Growth Hormone Secretion Research Articles

Somatic GNAS mutations in acromegaly: prevalence, clinical features and gender differences

Background: Somatic GNAS mutations are acknowledged as a significant etiological factor for acromegaly. However, the relationship between GNAS mutation status, clinical characteristics and gender has not been adequately investigated. This study aims to address these gaps by examining GNAS mutations and delineating the detailed clinical profile of affected patients within a Chinese acromegaly cohort. Methods: Our study encompassed 97 individuals newly diagnosed with acromegaly, who underwent surgical treatment between May 2015 and January 2022. We obtained DNA from frozen pituitary adenomas to screen for GNAS hotspot mutations and assessed the associated clinical characteristics. Results: In our cohort, 44.3% (43/97) of patients exhibited somatic GNAS mutations. Patients with mutations were predominantly male (58.1% vs. 33.3%, p=0.015), experienced longer diagnosis delays [72.0 (48.0, 120.0) vs 36.0 (21.0, 75.0) months, p=0.002], had smaller maximum tumor diameters (1.75±0.83 vs. 2.23±0.89 cm, p=0.008), and demonstrated higher rates of GH secretion per unit tumor volume [18.93 (9.67, 30.12) vs 10.91 (2.80, 20.40) ng/mL/cm3, p=0.005]. Regarding gender-specific differences, GNAS mutations in male patients were linked to significantly higher baseline GH levels [24.40 (14.40, 36.30) vs. 10.55 (5.25, 16.95) ng/mL, p=0.002], while female patients with mutations had notably smaller tumor sizes (1.55±0.55 cm vs. 2.32±0.85 cm, p<0.001). Conclusion: GNAS mutations are prevalent among Chinese acromegaly patients, correlating with reduced pituitary tumor sizes and enhanced GH secretion functions. Our findings underscore the influence of gender on the clinical manifestations of GNAS mutations. Accordingly, we recommend that future clinical and foundational researches on acromegaly give heightened consideration to gender-specific differences.

Co-expression of multiple transcription factors is associated with clinical features and endocrine prognosis in growth hormone-secreting pituitary adenomas.

The types of growth hormone-secreting pituitary adenomas are diverse, we have found that there are significant differences in clinical features and prognosis between PIT-1 single-cell spectrum growth hormone adenomas and growth hormone phenotypic polyhormonal adenomas. This study examined a cohort of 193 patients with growth hormone-secreting pituitary adenoma (GHPA), stratifying them into two groups: PIT-1 single transcription factor positive growth hormone adenoma (STF-GHPA) and Multiple transcription factor-positive growth hormone-secreting adenomas (MTF-GHPA). The objective was to compare these two groups' clinical characteristics. Within the MTF-GHPA group, we further subtyped them based on transcription factors to evaluate potential variations in clinical manifestations. Logistic regression analyses were employed to develop a risk factor model for investigating factors influencing hormone remission. There were no statistically significant differences in terms of age, gender, serum GH, and IGF-1 levels between patients diagnosed with MTF-GHPA and STF-GHPA. However, patients with MTF-GHPA exhibited a higher proportion of hypopituitarism compared to those with STF-GHPA. Furthermore, MTF-GHPA were characterized by smaller tumor size and less invasiveness, as indicated by lower Knosp classes. However, patients with MTF-GHPA have a lower rate of hormonal remission (30.8%) and more postoperative complications (31.0%), which means that STF-GHPA (hormonal remission:71.6%; postoperative complications:13.4%) has a better endocrine outcome than MTF-GHPA patients. Between the PIT-1 + SF-1+ and PIT-1 + TPIT+ subtypes within MTF-GHPA, significant differences were also observed in tumor size, endocrine outcomes, and postoperative complications. Risk factors influencing hormonal remission for GHPA included preoperative GH level, primary/recurrent, extent of resection, and transcription factor expression. Co-expression of multiple transcription factors is an important factor associated with clinical behavior and endocrine outcomes in patients with GHPA.

Characterization and Regulation of the Neonatal Growth Hormone Surge.

High neonatal growth hormone (GH) secretion has been described in several species. However, the neuroendocrine mechanisms behind this surge remain unknown. Thus, the pattern of postnatal GH secretion was investigated in mice and rats. Blood GH levels were very high on postnatal day (P)1 and progressively decreased until near zero by P17 in C57BL/6 mice without sex differences. This pattern was similar to that observed in rats, except that female rats showed higher GH levels on P1 than males. In comparison, follicle-stimulating hormone exhibited higher secretion in females during the first 3 weeks of life. Hypothalamic Sst mRNA and somatostatin neuroendocrine terminals in the median eminence were higher in P20/P21 mice than in newborns. Knockout mice for GH-releasing hormone (GHRH) receptor showed no GH surge, whereas knockdown mice for the Sst gene displayed increased neonatal GH peak. Leptin deficiency caused only minor effects on early-life GH secretion. GH receptor ablation in neurons or the entire body did not affect neonatal GH secretion, but the subsequent reduction in blood GH levels was attenuated or prevented by these genetic manipulations, respectively. This phenotype was also observed in knockout mice for the insulin-like growth factor-1 (IGF-1) receptor in GHRH neurons. Moreover, glucose-induced hyperglycemia overstimulated GH secretion in neonatal mice. In conclusion, GH surge in the first days of life is not regulated by negative feedback loops. However, neonatal GH secretion requires GHRH receptor, and is modulated by somatostatin and blood glucose levels, suggesting that this surge is controlled by hypothalamic-pituitary communication.

Exogenous Opioids and the Human Endocrine System: An Endocrine Society Scientific Statement.

The use and misuse of opioids are a growing global problem. Although the effects of these drugs on the human endocrine system have been studied for decades, attention on their related clinical consequences, particularly on the hypothalamic-pituitary system and bone health, has intensified over recent years. This Statement appraises research data related to the impact of opioids on the gonadal and adrenal function. Whereas hypogonadism is well recognized as a side effect of opioids, the significance of their inhibitory actions on the hypothalamic-pituitary-adrenal system and the occurrence of clinically relevant adrenal insufficiency is not fully elucidated. The often-inconsistent results of studies investigating how opioids affect the secretion of GH, prolactin, arginine vasopressin, and oxytocin are assessed. The accumulating evidence of opioid actions on bone metabolism and their negative sequelae on bone mineral density and risk of fracture are also reviewed. In each section, available data on diagnostic and management approaches for opioid endocrine sequelae are described. This Statement highlights a plethora of gaps in research associated with the effects and clinical consequences of opioids on the endocrine system. It is anticipated that addressing these gaps will improve the care of people using or misusing opioids worldwide. The Statement is not intended to serve as a guideline or dictate treatment decisions.

D-Aspartate Stimulates Growth Hormone Secretion in Wethers.

Growth hormone (GH) is an essential factor in enhancing the productivity of animals. In ruminants, L-aspartate (L-Asp) stimulates the secretion of GH; however, the effect of D-Asp on GH remains unknown. Here, we examined the effect of D-Asp on GH secretion in wethers. Blood GH, insulin, adrenaline, noradrenaline, non-esterified fatty acid (NEFA), and glucose concentrations were evaluated in response to the intravenous infusion of a high-dose (0.1 mmol/kg/min) of D-Asp for 20min. Further, concentrations of these biomolecules were evaluated when a low-dose (0.05 mmol/kg/min) of D-Asp was continuously infused intravenously for 20min. Finally, the direct effect of D-Asp on GH secretion was determined using cultured sections of the anterior pituitary tissue from wethers. Infusion of the high-dose of D-Asp markedly increased blood GH concentrations (P < 0.05), resulting in an increase in the area under the curve (AUC). Plasma GH concentrations and AUC also increased in response to infusion of a low D-Asp dose. Infusion of a high and low D-Asp dose caused a prolonged reduction in plasma insulin concentrations, and the AUC was lower (P < 0.05). Plasma NEFA concentrations gradually increased after the end of D-Asp infusion, with a low D-Asp dose infusion resulting in significantly higher concentrations at 90min (P < 0.05). Plasma adrenaline, noradrenaline, and glucose concentrations did not show significant changes despite differences in the dose of D-Asp. Although D-Asp treatments stimulated GH secretion in the cultured sections of pituitary tissues, the effect was not significant. These results suggest that D-Asp stimulates the secretion of GH in wethers through not only a direct action on the pituitary gland but also through another pathway of GH stimulation.

Hsa_circ_0002473 inhibits GH3 cell proliferation and GH secretion as a competitive endogenous RNA for has-miR-4645-3p.

Growth hormone deficiency (GHD) diagnosis still lacks a gold standard or ideal diagnostic marker. Unlike other epigenetic mechanisms, non-coding RNAs regulate post-transcriptional levels. The information on non-coding RNAs in the field of GHD is limited. Therefore, this study aimed to explore the role of hsa_circ_0002473 as a competitive endogenous RNA for has-miR-4645-3p in attenuating the inhibitory effect of has-miR-4645-3p on SSTR2. In this study, we screened three significantly expressed circular RNAs (circRNAs) in five children with GHD, and selected the highest expressed hsa_circ_0002473 as the study object, and screened has-miR-4645-3p, which is the most likely to bind to hsa_circ_0002473, according to the microRNA (miRNA)-circRNA regulatory network, to study the role and mechanism of has-miR-4645-3p as a competitive endogenous RNA of has-miR-4645-3p on GH3 cells. Somatostatin receptor 2 (SSTR2) inhibits GH3 cell proliferation, and miRNA binding to SSTR2 inhibits the latter expression. Both bioinformatics and dual-luciferase reporter analyses showed targeting relationships between hsa_circ_0002473 and has-miR-4645-3p and between has-miR-4645-3p and SSTR2. We constructed the hsa_circ_0002473/has-miR-4645-3p axis and transfected it into GH3 cells and found that overexpression of hsa_circ_0002473 inhibited the proliferation and growth hormone (GH) secretion of GH3 cells, and that hsa-miR-4645-3p promoted the proliferation and GH secretion of GH3 cells by targeting SSTR2. Co-culture revealed that the inhibitory effect of hsa_circ_0002473 was reversed by has-miR-4645-3p. In conclusion, our findings suggest that hsa_circ_0002473 can act as a competitive endogenous RNA for has-miR-4645-3p to regulate GH3 cell proliferation and secretion by targeting SSTR2.

Mixed Gangliocytoma-Pituitary Adenoma: Incidental Discovery During Eye Injury Evaluation: A Case Study

Abstract Introduction/Objective Mixed gangliocytoma-adenoma is exceedingly rare, representing less than 0.5% of sellar tumors. We present a unique case of mixed gangliocytoma-pituitary adenoma incidentally diagnosed during the evaluation of traumatic eye injury. We aim to clarify the diagnostic process using real clinical data, stressing how such cases might be missed without careful histopathological examination Methods/Case Report A 32-year-old male presented for elective transsphenoidal resection (TSR) due to a suspected growth hormone (GH) secreting pituitary tumor. Surprisingly, the adenoma was discovered incidentally during an eye injury evaluation. Referred from an ophthalmology clinic, initial concerns were a possible blood clot or foreign body in the left eye, following a forceful encounter with a tree branch Results (if a Case Study enter NA) Imaging incidentally identified a 2 cm pituitary mass. Further evaluation showed elevated levels of insulin-like growth factor 1 (IGF1) at 1162 ng/ml and GH at 10.2 ng/ml. Remarkably, the patient had not observed signs of acromegaly, until photographic comparison between past and present appearances was made. TSR of the pituitary mass was done. Microscopic examination revealed monomorphic cells with round nuclei with the typical speckled chromatin pattern of neuroendocrine cells with cytoplasm ranging from chromophobic to eosinophilic, consistent with pituitary adenoma. An additional unexpected finding was the presence of large gangliocytic cells (large neurons), dispersed throughout the tumor as single or clustered cells. In some regions, distinct patches of fine neuropil stroma were associated with the clustered ganglion cells. IHC staining with synaptophysin and neurofilament highlighted the gangliocytic component. CAM 5.2 IHC stain showed perinuclear dot-like expression in the adenoma cells, GH IHC showed patchy expression, and prolactin IHC was expressed in scattered cells. Ki67 index was ~ 2%. There was no evidence of necrosis nor mitosis. The coexistence of sellar gangliocytoma with pituitary adenoma, as observed in this case, represents a rare entity known as mixed gangliocytoma-pituitary adenoma Conclusion The adenomatous component of mixed gangliocytoma-pituitary adenoma often secrete GH, leading to its classification as pituitary somatotroph adenoma. This poses a diagnostic challenge due to the lack of specific symptoms or unique brain imaging features, necessitating thorough histological evaluation for precise diagnosis and to ensure the gangliocytoma component is not overlooked

Acromegalia em felinos

Acromegaly in felines occurs mainly due to a pituitary adenoma of somatotropic cells, and presents slow and progressive evolution, responsible for increasing the production and secretion of growth hormones (GH). This condition is common in senile or adult male domestic cats, neutered and with short hair. The pathophysiology is due to the excessive release of GH in the adenohypophysis region, whose synthesis is regulated by growth hormone-releasing hormone (GHRH) and somatostatin, responsible for stimulating or inhibiting the secretory axis, respectively. The anabolic action of GH is responsible for increasing the secretion of IGF-1, which is mainly responsible for the clinical signs of acromegaly, such as body growth and organomegaly. The catabolic effect refers to insulin resistance. Clinical signs may be associated with secondary diabetes mellitus (DM), weight gain, exacerbated growth of various tissues and neurological signs as the tumor mass grows. The diagnosis of the disease can be performed through laboratory, imaging and endocrine tests such as the specific immunoassay for GH and/or insulin-like growth factor 1 (IGF-1). Treatment is based on controlling the DM that develops secondary to it, as well as on attempts to reduce or even inhibit the excess release of GH. Treatment can be performed with somatostatin analogues and dopamine agonists. The use of stereotactic radiotherapy can also be recommended, with favorable results for tumor reduction, as well as the surgical technique of transsphenoidal hypophysectomy, which presents better results than other techniques but is a complex surgical procedure. This project aims to inform veterinarians of this endocrine disease and its main currently recognized diagnoses and treatments, emphasizing the need to establish a differential diagnosis for difficult-to-control DM.

The clinical and genetic aspects of six individuals with GH1 variants and isolated growth hormone deficiency type II.

Isolated growth hormone deficiency type II (IGHD II) is an autosomal dominant disorder characterized by a GH1 gene variant resulting in a significant reduction in growth hormone (GH) secretion and a subsequent decrease of plasma insulin-like growth factor 1 (IGF-1) levels and eventual growth impairment. This study aimed to identify causative variants in six Chinese families with IGHD II, exploring both clinical and genetic characteristics. Detailed clinical data, including clinical presentations, physical charateristics, medical and family histories, as well as genetic test results, were systematically examined. Six children, comprising four males and two females, with a mean age of 4.64 ± 1.15 years, exhibited short stature with a mean height of -3.95 ± 1.41 SDS. Four of them had a family history of short stature, while one patient presented with pulmonary hypertension. All children demonstrated GH deficiency in growth hormone stimulation tests (mean peak GH value: 2.83 ± 2.46 ng/mL). Exome sequencing for the six patients and targeted gene sequencing for their family members revealed heterozygous variants in the GH1 gene, including Exon2-5del, c.334T>C, c.291 + 1G>A, c.291 + 2T>A, 1.5 kb deletion, and 1.7 kb deletion, with four variants being novel. Four patients underwent human recombinant growth hormone (rhGH) replacement therapy, initiating treatment at a mean age of 4.6 ± 0.7 years. The mean height increase in patients was 1.21 ± 0.3 SDS in the first six months of treatment and 1.79 ± 0.15 SDS in the first year. Our findings contribute to expanding the genotypic and phenotypic spectra of individuals with IGHD II.

9318 Growth Response To Oral Growth Hormone Secretagogue LUM-201 In Children With Moderate GH Deficiency (GHD) Is Dependent On The Pattern Of Pulsatile GH Secretion Induced By LUM-201

Abstract Disclosure: A. Roslan: None. R. Roman: None. A. Avila: None. D. Said: None. I. Baier: None. E. Brincks: Employee; Self; Lumos Pharma, Inc.. Stock Owner; Self; Lumos Pharma, Inc. A. Bruchey: Employee; Self; Lumos Pharma, Inc.. Stock Owner; Self; Lumos Pharma, Inc. J. McKew: Employee; Self; Lumos Pharma, Inc.. Stock Owner; Self; Lumos Pharma, Inc. P. Pitukcheewanont: Employee; Self; Lumos Pharma, Inc.. Stock Owner; Self; Lumos Pharma, Inc.. M. Johnson: None. T. Garner: Consulting Fee; Self; Lumos Pharma, Inc.. Grant Recipient; Self; Novo Nordisk. M.O. Thorner: Consulting Fee; Self; Lumos Pharma, Inc.. Stock Owner; Self; Lumos Pharma, Inc. P.E. Clayton: Advisory Board Member; Self; Lumos Pharma, Inc.. Consulting Fee; Self; Lumos Pharma, Inc.. Grant Recipient; Self; Novo Nordisk. A. Stevens: Consulting Fee; Self; Lumos Pharma, Inc. F. Cassorla: Consulting Fee; Self; Lumos Pharma, Inc.. Background: Oral GH secretagogue, LUM-201, increases growth rates in children with moderate GHD in Phase 2 trials (OraGrowtH210 and 212) [ENDO 2023, OR21-06]. GH pulse profiles at baseline (D1) and 6 months (6M) were assessed in OraGrowtH212. This study aims to understand relationships between pulse profiles and growth response to LUM-201. Methods: The OraGrowtH212 trial is being conducted at a single site (Chile). 22 prepubertal children (M 14: F 8) with moderate GHD (peak GH level on two stimulation tests &amp;gt;3 and &amp;lt;10ng/ml), who had basal IGF-I &amp;gt;30ng/ml and an acute GH response to 0.8mg/kg LUM-201 of ≥5ng/ml, were randomised to receive LUM-201 1.6 or 3.2 mg/kg/day. 10min samples over 12hrs (08.00-20.00) were collected at D1 and M6 for measurement of GH concentration (ng/ml), with GH secretion rates (ng/ml/min) derived by deconvolution analysis. A univariate Spearman’s rank correlation matrix was used to screen for relationships (significant at p&amp;lt;0.05) between D1 characteristics, D1 height velocity, 6M annualised height velocity (AHV) and interpulse, pulsatile and total GH secretion at D1 and M6.The pattern of pulsatile GH secretion in the 12hr profile was characterised using Functional Principal Component Analysis (FPCA) - used to explore the dominant modes of variation in functional data, in this case the GH time series. Subjects were grouped into tertiles based on 6M AHV (High [mean 8.9cm/yr], Medium [7.7], and Low [6.7]), and the 12hr profiles were divided into three 4hr intervals. The interquartile range (IQR) for mean GH secretion (representing variation in amount) and principal components [PCs] (variation in pattern) for all subjects in each AHV tertile at D1 and M6 were generated. Results: All GH secretion parameters increased significantly from D1 to M6 (p&amp;lt;0.01). Age was negatively associated with 6m AHV (rs= -0.46), and D1 pulsatile GH secretion was positively associated with D1 AHV (rs = +0.51). However, GH secretion at D1 and M6 was not correlated with 6m AHV. In the FPCA, the difference in IQR for mean GH secretion from D1 to 6M was highest over 0-4hrs for subjects in the high and medium AHV tertiles (5- and 3.3-fold greater respectively compared to the other time intervals), while subjects with low AHV had the highest difference over 8-12hrs (42-fold greater). Using the first PC (which accounts for ∼50% of total variation), the change in IQR was highest over 0-4 and 4-8hrs in the high AHV tertile (3-fold greater compared to other time intervals), over 0-4hrs in the medium tertile (46-fold greater) and over 8-12hrs in the low tertile (3.4-fold greater). Conclusions: Oral LUM-201 stimulates significant increases in GH secretion over 6 months in children with moderate GH deficiency. Complex relationships exist between growth response and both the amount and pattern of GH secretion, with the highest growth responses to LUM-201 associated with the greatest pulsatile activity early in the profile. Presentation: 6/3/2024

6877 Withdrawing Growth Hormone Treatment at Mid-Puberty in Idiopathic Isolated Growth Hormone Deficiency: Baseline Characteristics in Patient-Preference Design Study

Abstract Disclosure: J. Vliegenthart: None. J. Wit: None. B. Bakker: None. A. Boot: None. C. de Bruin: None. M. Finken: None. J.V. Heyden: None. M. Houdijk: None. H. van der Kamp: None. E. Van Mil: None. A. Reedijk: None. T. Sas: None. D.A. Schott: None. P. van Setten: None. S. Straetemans: None. V. van Tellingen: None. B. Touwslager: None. A.V. Trotsenburg: None. P. voorhoeve: None. A.C. Hokken-Koelega: None. D.C. van der Kaay: None. Background: The majority of children diagnosed with idiopathic isolated growth hormone deficiency (IIGHD) show a normal growth hormone (GH) secretion (assessed by GH stimulation tests) when retested at near adult height (NAH). It appears plausible that, if normal stimulated GH secretion is observed in mid-puberty, continuing recombinant human GH (rhGH) treatment may only have a minor effect on NAH. The effect on NAH has never been investigated in a prospective study. Aim: To evaluate patient preference in the choice to (dis-)continue GH treatment from mid-puberty, and to study whether patients who discontinued treatment differed in baseline characteristics from those who continued treatment. Methods: The study population consisted of adolescents who were diagnosed in childhood with IIGHD (GH peak at diagnosis between 1.7 ug/L and 10 ug/L) and who had started rhGH therapy between 2005-2018. According to the national treatment protocol, GH secretion was retested in mid-puberty (males: Tanner stage G3/4, testicular volume &amp;gt;12 ml and bone age (BA) 13-16 years; females: Tanner stage B3/4 and BA 11-14 years). In this multicentre prospective patient-preference design study, adolescents who tested GH sufficient at mid-puberty (GH peak &amp;gt;6.7 ug/L) had the choice to discontinue or continue rhGH treatment until NAH (height velocity &amp;lt;2cm/year). Results: In total 127 patients (95 male, 75%) participated in this study. Forty-four patients (35%) chose to continue GH treatment until NAH (group 1), and 83 patients (65%) chose to discontinue GH treatment (group 2). Mean height at inclusion (group 1: -0.76±0.69 SDS vs group 2: -0.47±0.85 SDS; P=0.055), target height SDS (group 1: -0.73±0.54 SDS and -0.58±0.53 SDS, P=0.15) and age at inclusion (group 1: 14.0±1.1y and 13.9±1.1y, P=0.69) did not significantly differ between groups. Males and females did not differ in these characteristics. Currently, 109 patients (86%) have reached NAH. Conclusions: The majority of patients (65%) preferred to discontinue rhGH treatment after sufficient GH retesting in mid-puberty. An anticipated difference in baseline data between the groups (adolescents who choose to discontinue treatment may be taller and older) could not be confirmed. Data are being collected until all patients reach near adult height. Presentation: 6/3/2024

5162 Oral LUM-201 Restores Pulsatile Growth Hormone Secretion and Growth Response in Moderate Pediatric Growth Hormone Deficiency (PGHD): Key Discoveries from Phase 2 of OraGrowtH212 Trial

Abstract Disclosure: F. Cassorla: Consulting Fee; Self; Lumos Pharma, Inc. Research Investigator; Self; Lumos Pharma, Inc. R. Roman: Research Investigator; Self; Lumos Pharma, Inc. M.L. Johnson: Consulting Fee; Self; Lumos Pharma, Inc. A. Avila: Research Investigator; Self; Lumos Pharma, Inc. G. Iñiguez: Research Investigator; Self; Lumos Pharma, Inc. I. Baier: Research Investigator; Self; Lumos Pharma, Inc. D. Said: Research Investigator; Self; Lumos Pharma, Inc. A. Bruchey: Employee; Self; Lumos Pharma, Inc.. Stock Owner; Self; Lumos Pharma, Inc. C. Smith: Employee; Self; Lumos Pharma, Inc.. Stock Owner; Self; Lumos Pharma, Inc. E. Brincks: Employee; Self; Lumos Pharma. Stock Owner; Self; Lumos Pharma, Inc. J. McKew: Employee; Self; Lumos Pharma. Stock Owner; Self; Lumos Pharma. M.O. Thorner: Consulting Fee; Self; Lumos Pharma, Inc.. Stock Owner; Self; Lumos Pharma, Ammonett Pharma LLC. P. Pitukcheewanont: Employee; Self; Lumos Pharma. Stock Owner; Self; Lumos Pharma. Objectives: The primary objective was to examine the pharmacokinetic/pharmacodynamic (PK/PD) aspects of oral LUM-201 at doses of 1.6 and 3.2 mg/kg/d with moderate PGHD, involving frequent GH sampling for 12 hours post-administration. Using deconvolutional analysis, the study compared the GH secretion patterns before &amp; after 6 months (m) daily administration of LUM-201. LUM-201, an investigational agonist of the growth hormone (GH) Secretagogue Receptor 1a (GHSR1a), was employed as part of a predictive enrichment marker (PEM) test to identify moderate PGHD subjects likely to respond, based on baseline insulin-like growth factor-1 (IGF-1) level &amp;gt;30 ng/mL &amp; a peak GH of ≥5 ng/mL post a single 0.8 mg/kg dose of LUM-201. Methods: The OraGrowtH212 Trial, conducted at Santiago, Chile, monitors subjects until they approach their near final height. The current report focuses on data analysis at 6 and 12m, with ongoing subject follow-ups extending to 24m. This trial randomized 22 PEM+ moderate PGHD subjects into two LUM-201 dosage groups: 1.6 or 3.2 mg/kg/d. To assess GH secretion, each child was sampled every 10 min from 0800-2000h at baseline &amp; 6m. Safety was assessed throughout the study and growth evaluated at 6 &amp; 12m intervals. Results: At start of the study, basal GH secretion in the LUM-201 1.6mg/kg/d group (all values expressed as mean ± SD µg/kg body weight) was 0.19 ±0.09, pulsatile GH was 1.17 ± 0.66, and total GH was 1.35 ± 0.66. At 6m, each of these parameters had significantly increased to 0.36 ± 0.21, 1.8 ±0.74 and 2.2 ±0.89 respectively (p values from 0.02-0.04). Similar significant increases were seen for LUM-201 3.2mg/kg/d. Combining the data from both LUM-201 doses demonstrated that GH secretion determined by deconvolution analysis was 3.3-4.0 µg/kg/24hrs compared to 5 µg/kg/24hrs derived from published data on normal children (Zadik et al, Horm Res 1992), indicating restoration of GH secretion by LUM-201. These values are considerably less than 25-34µg/kg/d of recombinant human GH used in the treatment of PGHD. At 6m, the annualized height velocity (AHV) was 7.2cm/yr for the LUM-201 1.6mg/kg/d and 8.1cm/yr for the 3.2 mg/kg/d dose. At 12m, AHV for a subset was 6.9cm/yr for the 1.6 dose and 7.2cm/yr for the 3.2 dose. Baseline IGF-1 SDS (mean ±SD) were -1±0.63 in 1.6mg/kg/d group &amp; -0.85±0.47 in 3.2mg/kg/d group. The change over 12m was +0.9 on 1.6 dose and +1.1 on 3.2 dose, indicating similar efficacy for IGF-1 generation. LUM-201 showed good tolerability in this study, with no observed safety concerns in adverse events (AEs), labs, and ECGs. Conclusions: At 6m LUM-201 was able to restore endogenous GH pulsatile secretion to a similar level to that seen in normal children, while normalizing serum IGF-1 concentrations. These results indicate that by restoring endogenous GH secretion, LUM-201 facilitates growth utilizing a much lower amount of GH than that provided by daily exogenous rhGH administration. Presentation: 6/3/2024

9262 Withdrawing Growth Hormone Treatment at Mid-Puberty in Idiopathic Isolated Growth Hormone Deficiency: Baseline Characteristics in Patient-Preference Design Study

Abstract Disclosure: J. Vliegenthart: None. J. Wit: None. B. Bakker: None. A. Boot: None. C. de Bruin: None. M. Finken: None. J.V. Heyden: None. M. Houdijk: None. H. van der Kamp: None. E. Van Mil: None. A. Reedijk: None. T. Sas: None. D.A. Schott: None. P. van Setten: None. S. Straetemans: None. V. van Tellingen: None. B. Touwslager: None. A.V. Trotsenburg: None. P. voorhoeve: None. A.C. Hokken-Koelega: None. D.C. van der Kaay: None. Background: The majority of children diagnosed with idiopathic isolated growth hormone deficiency (IIGHD) show a normal growth hormone (GH) secretion (assessed by GH stimulation tests) when retested at near adult height (NAH). It appears plausible that, if normal stimulated GH secretion is observed in mid-puberty, continuing recombinant human GH (rhGH) treatment may only have a minor effect on NAH. The effect on NAH has never been investigated in a prospective study. Aim: To evaluate patient preference in the choice to (dis-)continue GH treatment from mid-puberty, and to study whether patients who discontinued treatment differed in baseline characteristics from those who continued treatment. Methods: The study population consisted of adolescents who were diagnosed in childhood with IIGHD (GH peak at diagnosis between 1.7 ug/L and 10 ug/L) and who had started rhGH therapy between 2005-2018. According to the national treatment protocol, GH secretion was retested in mid-puberty (males: Tanner stage G3/4, testicular volume &amp;gt;12 ml and bone age (BA) 13-16 years; females: Tanner stage B3/4 and BA 11-14 years). In this multicentre prospective patient-preference design study, adolescents who tested GH sufficient at mid-puberty (GH peak &amp;gt;6.7 ug/L) had the choice to discontinue or continue rhGH treatment until NAH (height velocity &amp;lt;2cm/year). Results: In total 127 patients (95 male, 75%) participated in this study. Forty-four patients (35%) chose to continue GH treatment until NAH (group 1), and 83 patients (65%) chose to discontinue GH treatment (group 2). Mean height at inclusion (group 1: -0.76±0.69 SDS vs group 2: -0.47±0.85 SDS; P=0.055), target height SDS (group 1: -0.73±0.54 SDS and -0.58±0.53 SDS, P=0.15) and age at inclusion (group 1: 14.0±1.1y and 13.9±1.1y, P=0.69) did not significantly differ between groups. Males and females did not differ in these characteristics. Currently, 109 patients (86%) have reached NAH. Conclusions: The majority of patients (65%) preferred to discontinue rhGH treatment after sufficient GH retesting in mid-puberty. An anticipated difference in baseline data between the groups (adolescents who choose to discontinue treatment may be taller and older) could not be confirmed. Data are being collected until all patients reach near adult height. Presentation: 6/3/2024

7248 Spliceosome component TCERG1 regulates the aggressiveness of somatotroph adenoma

Abstract Disclosure: K. Kim: None. The role of the spliceosome in the development of pituitary tumors is not well understood, despite preliminary studies indicating abnormal expression of oncogenic splicing variants in these neuroendocrine tumors. We aimed to identify differentially expressed spliceosome components in growth hormone (GH)-secreting pituitary tumors and investigate their roles in pathogenesis.We performed transcriptome analysis of 20 somatotroph adenomas and 6 normal pituitary tissues to select dysregulated spliceosome components. Clinical characteristics were analyzed based on gene expression in 64 patients with acromegaly. GH secreting pituitary adenomas were confirmed by 75 g oral glucose tolerance and immunohistochemical staining. Proliferation, invasion, and hormonal activity of GH secreting pituitary adenoma cells were investigated after modulating gene expression.TCERG1 expression was significantly higher in somatotroph adenomas than in normal cells (log2 fold change 0.59, adjusted P=0.0002*). Genotype-phenotype analysis revealed that patients with higher TCERG1 expression had lower surgical remission rates than those with lower expression (63.64% vs. 95.45%, P=0.009*). TCERG1 expression was significantly higher in groups with cavernous sinus (CS) invasion or Ki67 index over 1.5 (2.06 vs. 1.65, P=0.011*; 2.02 vs. 1.66, P=0.043*). TCERG1 overexpression led to a 16.91% increase in proliferation after 72 h (P&amp;lt;0.001*) and a 249.47% increase in invasion after 48 h in GH3 cells (P=0.026*). Conversely, TCERG1 silencing significantly decreased cell proliferation (10.15% at 72 h, P&amp;lt;0.001*) and invasion (96.87% at 48 h, P=0.029*). Vimentin was increased, but E-cadherin was decreased in both TCERG1 overexpressed GH3 cells and somatotroph adenomas. And TCERG1 silence reversed the expression of the genes (CDH2, SNAI1, ZEB2, and VIM) in GH3 cells. Additionally, GH secretion increased when TCERG1 was overexpressed in GH3 cells. Spliceosome machinery provide novel insights into the pathogenesis of GH-secreting pituitary tumor and highlight the potential role of TCERG1 as a therapeutic target. Presentation: 6/2/2024

6743 Decline in IGF-1 after surgery of the nonfunctioning pituitary neuroendocrine tumor

Abstract Disclosure: J. Sugata: None. S. Fujio: None. R. Makino: None. T. Hanada: None. R. Hanaya: None. Background: Patients undergoing surgical treatment for nonfunctioning pituitary neuroendocrine tumors (PitNET) may experience impaired secretion of growth hormone (GH). The optimal timing for assessing GH secretory function postoperatively remains unclear. In our department, we typically conduct hormone-loading tests three months after surgery. However, even in some cases without a diagnosis of growth hormone deficiency (GHD) at that point, there might be a gradual decline in Insulin-like growth factor-1 (IGF-1). Methods: We studied patients who exhibited peak GH levels &amp;gt; 1.8ng/ml in an insulin tolerance test (ITT) three months after undergoing surgery for nonfunctioning PitNET. We evaluated the levels of IGF-1 during the last observation, excluding cases where reoperation or radiosurgery was performed. Results: We identified 67 cases (29 males, 38 females) meeting the study criteria, with a median age of 54 years. The median follow-up time spanned 6 years (range 1-13 years). The median standard deviation (SD) scores of IGF-1 three months after surgery were -0.96, with 14 cases (21%) below -2.0 SD. At the end of the follow-up period, the median SD scores of IGF-1 were -1.31. This was significantly lower than the three-month time point (p&amp;lt;0.01), and 21 cases (31%) recorded were below -2.0 SD. In 6 cases suspected of severe GHD due to subjective symptoms or decreased IGF-1, ITT, or GH-releasing peptide-2 were retested. Among these, 2 cases were diagnosed with severe GHD, while the remaining demonstrated normal secretion of GH despite the low concentration of IGF-1. The IGF-1 SD scores at the end of follow-up and the three-month time-point exhibited a significant correlation (R2=0.74, p&amp;lt;0.01). However, no correlation was found between IGF-1 scores and peak GH concentration, age, tumor size, pituitary apoplexy, or preoperative IGF-1 SD scores. Conclusions: IGF-1 exhibited a progressive decrease in the majority of cases without severe GHD, with some cases showing reductions greater than -2.0 SD. Our findings emphasize the importance of cases with long-term clinical follow-up low IGF-1 after PitNET surgery, even when GH secretion appears normal. Presentation: 6/1/2024

8396 Growth Hormone Secretion after Glucagon Stimulation is Increased in Individuals with History of Bariatric Surgery

Abstract Disclosure: L. Pei: None. C. Cummings: None. H. Saeed: None. M. Farahmandsadr: None. A. Amore: None. A. Sheehan: None. R. Ferraz-Bannitz: None. D.C. Simonson: Stock Owner; Self; GI Windows. Other; Self; wife owns Phase V Technologies. M. Patti: Advisory Board Member; Self; data and safety monitoring board on Fractyl Health. Consulting Fee; Self; AstraZeneca, Hamni, MBX Biosciences. Grant Recipient; Self; Receive investigator-initiated research funding from Dexcom. Background: Growth hormone (GH) is an important counterregulatory hormone and regulator of hepatic glucose metabolism. Previous studies demonstrated increased plasma GH and reduced plasma growth hormone receptor (GHR) after bariatric surgery in both rodents and humans. Moreover, plasma GHR was identified as mediator of improved glycemic control after Roux-en-Y gastric bypass (RYGB). We now test the hypothesis that altered GH and/or GHR levels contribute to post-bariatric hypoglycemia (PBH). Methods: Cross-sectional studies were performed at a single academic institution. GH secretion was assessed after 1mg IV glucagon (GCG) and during hyperinsulinemic-hypoglycemic clamp in 3 groups: 1) post-RYGB without hypoglycemia symptoms (RnonH) (20F, age 51±11 (mean±SD) y, BMI 35±8 kg/m2, HbA1c 5.2±0.3%, 10.6±5.3 years post-surgery), 2) PBH (18F/2M, age 54±12y, BMI 30.5±4.6 kg/m2, HbA1c 5.2±0.3%, 9.4±6.0 years post-surgery), 3) weight-similar controls without upper GI surgery (CON) (6F/4M, age 47.1±13.1y, BMI 31.9±5.7 kg/m2, HbA1c 5.4±0.3%). Plasma GHR and GH were measured via ELISA. Results: Fasting GH did not differ between groups (mean±SE, CON: 285±78, RnonH: 860±179, PBH: 980±284 pg/mL, P=0.16). Peak incremental glucose response to GCG, ranging from 46-59 mg/dL, did not differ between groups. At 120 min after GCG, GH was significantly higher in both PBH and RnonH vs. CON (PBH: 3018±678, RnonH: 2521±656, CON: 481±137 pg/mL, ANOVA P= 0.012, PBH vs. CON P=0.003, RnonH vs. CON P=0.02). Peak GH in PBH was significantly higher vs. CON (3431± 655 vs. 547±153 pg/mL, P=0.03), but did not differ in RnonH vs. PBH. Peak GH was inversely correlated with postoperative duration in PBH only (r=-0.49, P=0.03), with BMI in both surgical groups (PBH: r=-0.49, P=0.03, RnonH: r=-0.57, P=0.009) and with percent body fat (impedance plethysmography) in the combined surgical group (r=-0.51, P=0.0007). In contrast, GH during hyperinsulinemic hypoglycemia did not differ between groups (CON: 9660 ±2588, RnonH: 7759±1751, PBH: 7309±1549 pg/mL, P=0.3) at similar degrees of hypoglycemia (CON: 54.8±1.5, RnonH: 50.7±1.0, PBH: 50.9±1.4 mg/dL). Fasting plasma GHR did not differ (CON: 23.3±3.8, RnonH: 19.4±2.8, PBH: 13.8±2.1 ng/mL, P=0.10). GHR was correlated with percent fat mass in the combined surgical group (r=0.56, P=0.0003) but not in CON. Conclusion: Plasma GH did not differ as a function of prior RYGB, with or without hypoglycemia, in the fasting state or in response to insulin-induced hypoglycemia. However, GCG-stimulated GH levels were 5-6-fold higher in individuals with history of RYGB, numerically higher in PBH, and inversely related to body fat and postop duration. Together these results suggest that reduced GH is not likely driving hypoglycemia in PBH, but that alterations in glucagon-mediated GH secretion and/or action may contribute to observed metabolic effects of RYGB. Presentation: 6/1/2024

9228 Insulin-Like Growth Factor-1 Modulates Arcuate Kisspeptin Neuron Activity

Abstract Disclosure: J.N. Silva: None. R. Frazao: None. The kisspeptin-producing cells located at the arcuate nucleus of the hypothalamus (ARHKisspeptin) are considered the GnRH pulse generator necessary for fertility. In addition, ARHKisspeptin cells act as a metabolic sensor to control the hypothalamic-pituitary-gonadal (HPG) axis. The insulin-like growth factor-1 (IGF-1) is considered a component contributing to puberty onset and fertility. Peripherical or intracerebroventricular IGF-1 administration is sufficient to increase hypothalamic Kiss1 expression. However, whether IGF-1 acts directly on ARHKisspeptin cells to modulate the HPG axis is not known. To determine whether IGF-1 modulates ARHKisspeptin neuron activity, we used mice expressing the green fluorescent protein “humanized renilla” under the transcriptional control of the Kiss1 gene (8-10 weeks old). Fura-2 fluorescent probe was used to evaluate the state coupled or uncoupled to calcium in the face of IGF- 1 administration (0.5 μg/ml). Furthermore, whole-cell patch-clamp was employed to determine IGF-1 effects on ARHKisspeptin neuron's resting membrane potential (RMP). FURA-2 was incorporated by 64 ARHKisspeptin neurons out of 424 cells in the ARH. IGF-1 administration to the bath led to a significant increase of the intracellular calcium levels ([Ca2+]i) in 53% of ARHKisspeptin cells evaluated in male mice (34 out of 64 cells; IGF-1, 203.0 ± 26.1 nM; baseline period, 68.8 ± 9.6 nM; P&amp;lt; 0.0001). Non-responsive cells (30 out of 64 ARHKisspeptin neurons) exhibited average [Ca2+]i of 53.2 ± 6.3 nM after IGF-1 application vs 46.2 ± 5.6 nM in the baseline period (P= 0.3). Of note, IGF-1 also increased [Ca2+]i in 25% of non-kisspeptin cells in the ARH (93 out of 364 cells, IGF-1, 193.8 ± 12.4 nM; vs baseline period, 73.0 ± 5.6 nM, P&amp;lt; 0.0001). By evaluating the IGF-1 effects on ARHKisspeptin neuron’s RMP, we observed that IGF-1 tends to depolarize the RMP of 18% of cells recorded from males (4 out of 22 cells, IGF-1, -58.0 ± 3.0 mV; baseline, -64.1 ± 4.4 mV; P= 0.05), and depolarized the RMP of 44% of cells recorded from female mice (7 out of 16 cells, IGF-1, -61.1 ± 3.3 mV; baseline, -66.3 ± 2.7 mV; P= 0.002). Importantly, IGF-1-induced depolarization of ARHKisspeptin cells RMP was blocked when the recordings were performed in the presence of tetrodotoxin and ionotropic amino acid antagonists. Therefore, IGF-1-induced effects on ARHKisspeptin cells RMP depend on action potentials mediated by synaptic transmission. Our results suggest that IGF-1 indirectly modulates the activity of a large number of ARHKisspeptin neurons. Thus, situations of metabolic stress that induce changes in growth hormone secretion and, consequently, IGF-1 circulating levels, (e.g., fasting), can modulate the HPG axis through the indirect modulation of the activity of ARHKisspeptin cells. Presentation: 6/2/2024

8388 Insulin-Like Growth Factor-1 Modulates Arcuate Kisspeptin Neuron Activity

Abstract Disclosure: J.N. Silva: None. R. Frazao: None. The kisspeptin-producing cells located at the arcuate nucleus of the hypothalamus (ARHKisspeptin) are considered the GnRH pulse generator necessary for fertility. In addition, ARHKisspeptin cells act as a metabolic sensor to control the hypothalamic-pituitary-gonadal (HPG) axis. The insulin-like growth factor-1 (IGF-1) is considered a component contributing to puberty onset and fertility. Peripherical or intracerebroventricular IGF-1 administration is sufficient to increase hypothalamic Kiss1 expression. However, whether IGF-1 acts directly on ARHKisspeptin cells to modulate the HPG axis is not known. To determine whether IGF-1 modulates ARHKisspeptin neuron activity, we used mice expressing the green fluorescent protein “humanized renilla” under the transcriptional control of the Kiss1 gene (8-10 weeks old). Fura-2 fluorescent probe was used to evaluate the state coupled or uncoupled to calcium in the face of IGF- 1 administration (0.5 μg/ml). Furthermore, whole-cell patch-clamp was employed to determine IGF-1 effects on ARHKisspeptin neuron's resting membrane potential (RMP). FURA-2 was incorporated by 64 ARHKisspeptin neurons out of 424 cells in the ARH. IGF-1 administration to the bath led to a significant increase of the intracellular calcium levels ([Ca2+]i) in 53% of ARHKisspeptin cells evaluated in male mice (34 out of 64 cells; IGF-1, 203.0 ± 26.1 nM; baseline period, 68.8 ± 9.6 nM; P&amp;lt; 0.0001). Non-responsive cells (30 out of 64 ARHKisspeptin neurons) exhibited average [Ca2+]i of 53.2 ± 6.3 nM after IGF-1 application vs 46.2 ± 5.6 nM in the baseline period (P= 0.3). Of note, IGF-1 also increased [Ca2+]i in 25% of non-kisspeptin cells in the ARH (93 out of 364 cells, IGF-1, 193.8 ± 12.4 nM; vs baseline period, 73.0 ± 5.6 nM, P&amp;lt; 0.0001). By evaluating the IGF-1 effects on ARHKisspeptin neuron’s RMP, we observed that IGF-1 tends to depolarize the RMP of 18% of cells recorded from males (4 out of 22 cells, IGF-1, -58.0 ± 3.0 mV; baseline, -64.1 ± 4.4 mV; P= 0.05), and depolarized the RMP of 44% of cells recorded from female mice (7 out of 16 cells, IGF-1, -61.1 ± 3.3 mV; baseline, -66.3 ± 2.7 mV; P= 0.002). Importantly, IGF-1-induced depolarization of ARHKisspeptin cells RMP was blocked when the recordings were performed in the presence of tetrodotoxin and ionotropic amino acid antagonists. Therefore, IGF-1-induced effects on ARHKisspeptin cells RMP depend on action potentials mediated by synaptic transmission. Our results suggest that IGF-1 indirectly modulates the activity of a large number of ARHKisspeptin neurons. Thus, situations of metabolic stress that induce changes in growth hormone secretion and, consequently, IGF-1 circulating levels, (e.g., fasting), can modulate the HPG axis through the indirect modulation of the activity of ARHKisspeptin cells. Presentation: 6/2/2024

7518 A Case of Delayed Diagnosis of Acromegaly Associated with Uncontrolled Diabetes

Abstract Disclosure: A. Mahmoudabadi: None. S. Patel: None. Background: Acromegaly is a rare disorder characterized by an excess secretion of growth hormone (GH) and increased circulating insulin-like growth factor 1 (IGF-1) levels, typically due to a GH-secreting pituitary adenoma. This consequently leads to complications such as acral and soft tissue overgrowth, visual disturbance, insulin resistance, and dyslipidemia. In this case, we describe a patient who presented to the endocrinology clinic for uncontrolled diabetes and was subsequently diagnosed with acromegaly. Clinical Case: This is a 47-year-old male with a history of heart failure, hypertension, and type 2 diabetes mellitus (DM) who presented to the clinic with uncontrolled DM. He had failed to achieve adequate blood sugar control despite being compliant with metformin, dapagliflozin, and insulin degludec. Physical examination revealed frontal bossing, prognathism, macroglossia, and a deep voice. On further questioning, he had noticed these changes since five years prior. Anthropometry and laboratory tests were as follows: Height, 180 cm; body weight 107.5 kg; body mass index (BMI), 33.05 kg/m2 and A1c level of 15.0%. Suspicion of acromegaly was confirmed based on biochemical and imaging findings. Fasting growth hormone (GH), at 58 mU/L (reference range 0-10), and insulin-like growth factor 1 (IGF-1), at 857 nmol/L (reference range 81-263), were markedly elevated. Pituitary magnetic resonance imaging (MRI) showed a sellar and suprasellar mass (2.6 × 2.2 × 2.2 cm) extending and compressing the optic chiasm. He eventually underwent a transsphenoidal adenomectomy with neurosurgery. Following surgery, his insulin requirements went from a total daily dose of about 100 units to an inpatient dose of 30 units by his last day of admission. Conclusion: Acromegaly is prevalent in less than 3% of patients with DM, but higher rates of DM are seen in acromegalic patients with higher IGF-1 levels and longer duration of disease. The diagnosis of acromegaly can often be delayed due to missed findings on routine physical examination. This can lead to increased morbidity, mortality, and complications such as uncontrolled DM, witnessed in our patient. Surgical management of acromegaly is the mainstay of treatment and can lead to improvement of glycemic control and insulin sensitivity. Fortunately, our patient could undergo surgery, but delayed diagnosis can prevent patients from surgery if the pituitary tumor becomes too large or unresectable. Ultimately, this case highlights the importance of a thorough physical examination and keeping a wide differential diagnosis when evaluating patients with uncontrolled DM, as failure to diagnose acromegaly at an early stage may have devastating consequences on patient outcomes. Presentation: 6/3/2024

7795 Gender based differences in peripubertal growth patterns may offer insight into the twofold representation of boys compared to girls among children referred for growth hormone stimulation tests

Abstract Disclosure: Y. Dekel: None. L. Horowitz : None. R. Gendelman: None. M. Cohen: None. Background: Growth hormone (GH) stimulation tests are essential in the diagnostic assessment of pediatric GH deficiency (GHD). However, the tests bare multiple limitations, resulting from both intrinsic and child-related factors. Thus, referral decisions are key in making a correct diagnosis. Several studies demonstrated a gender bias in referral for short stature evaluation with a higher proportion of boys referred and diagnosed with GHD. Moreover, the boys had higher height z-scores upon referral. About 100 GH stimulation-tests are conducted annually at our pediatric endocrinology unit. We aimed to characterize the children that underwent GH stimulation-testing between 2017-2021, specifically focusing on differences based on: 1) gender 2) GH secretion status (deficient vs. sufficient). Methods: A retrospective review of charts of children aged 0-18 years that performed GH stimulation-tests at the Rambam pediatric endocrinology unit between the years 2017-2021 was conducted. Children followed at an outside clinic that had a first GH stimulation-test elsewhere, were excluded. Data was collected through the electronic database and by manually screening medical charts. The IBM SPSS statistics package 21 version was used for analysis. Results: Four-hundred children were included in the study, 266 boys (66.5%) and 134 girls (33.5%). Mean age 8.8±4.2 years, mean height z-score -2.3±0.7 and mean mid-parental height standard-deviation-scores (MPH-SDS) -0.6±0.7. The mean difference between MPH-SDS and child height-z-score was 1.7±0.8 SDS. Mean age was younger in girls compared with boys, 7.3±3.3 and 9.6±4.4 years respectively (p&amp;lt;0.001). Age distribution differed between genders, while refferals peaked between 3-4 years of age in both girls and boys, a second peak at 13-14 years of age was evident only in boys. Interestingly, there was no significant difference between boys and girls in height z-score, difference from MPH-SDS or rates of GHD. Overall, 93 (23.3%) children were diagnosed with GHD, 32 girls (24%) and 61 boys (23%). Children with GHD were younger and had higher BMI-SDSs compared to GH sufficient children, age 7.8±3.8, 9.2±4.3 years respectively (p=0.003), BMI z-score 0.17±1.38, -0.47±1.15 respectively (p&amp;lt;0.001). Conclusion: Twice as many boys than girls were referred for GH stimulation tests in our cohort. Based on differences in age distribution, the peripubertal physiologic growth deceleration that occurs later in boys, likely contributes to this finding. This male-to-female ratio is similar to ratios reported in the literature regarding short stature referrals; however, in contrast to the literature, in our cohort it could not be explained by an anthropometric bias in referral criteria. Presentation: 6/3/2024