ACTH Precursor Research Articles

RF09 | PSAT88 Pro-opiomelanocortin (POMC), ACTH and Cortisol Responses to Pediatric Cardiac Surgery

Abstract Introduction In critically ill adults, high plasma free cortisol in face of suppressed plasma ACTH coincides with high plasma pro-opiomelanocortin (POMC), the ACTH precursor (1). Further augmenting the systemic glucocorticoid availability with hydrocortisone treatment further lowered plasma ACTH, while plasma POMC remained unaffected (2). The dynamics of POMC in relation to ACTH and free cortisol prior to intensive care unit (ICU) admission are unknown, as well as the impact hereon of glucocorticoid treatment. Also, elevated plasma POMC concentrations have not yet been confirmed in pediatric ICU (PICU) patients. In pediatric cardiac surgery-induced critical illness, we hypothesized that plasma POMC is elevated and that plasma ACTH transiently rises per-operatively and becomes suppressed once free cortisol has risen on PICU day 1 and 2. In addition, we hypothesized that in patients receiving glucocorticoids per-operatively, plasma ACTH is further suppressed while plasma POMC is unaffected. Methods From 53 children aged 0-36 months, who underwent cardiac surgery and were admitted to the PICU, blood samples were taken prior to surgery (pre-operatively, available samples N=51), during surgery (per-operatively, N=47), on the following morning (PICU day 1, N=40) and the day hereafter (PICU day 2, N=24). Blood samples were also collected from 24 age- and gender-matched healthy children. To investigate the impact of synthetic glucocorticoid treatment on the endogenous plasma hormone concentrations, patients were categorized into steroid-naive (total N=38) and steroid-treated patients (total N=15). Plasma hormone concentrations were quantified with highly-specific ELISA (POMC), RIA (ACTH, cortisol, CBG) or colorimetric assays (albumin). Cross reactivity with synthetic glucocorticoids within the used cortisol RIA is minimal (<0.27% for methylprednisolone, <0.1% for dexamethasone). Free cortisol was estimated with the adapted Coolens’ formula. Results Plasma POMC was increased pre-operatively (p<0.0001) but no longer thereafter (p>0.05), irrespective of steroid treatment. Plasma ACTH in patients was never higher than in healthy children. While in steroid-naive patients, plasma ACTH became suppressed only by PICU day 1 (p<0.0001), steroid-treated patients had already suppressed plasma ACTH per-operatively (p≤0.0001). In steroid-naive patients, plasma free cortisol was increased from per-operatively onwards (p≤0.002), while in steroid-treated patients, plasma free cortisol (endogenous) concentrations always remained comparable to those of healthy children (p>0.05). Conclusion Pre-operatively high plasma POMC, not followed by increased ACTH, suggests a centrally-activated HPA-axis already prior to surgery and an immature pituitary processing of POMC into ACTH. Systemic glucocorticoid availability is elevated from surgery onwards, likely driven by ACTH-independent mechanisms. Further increasing systemic glucocorticoid availability exogenously with glucocorticoid administration accelerates the suppression of plasma ACTH. The long-term impact of early glucocorticoid treatment in critically ill children remains to be investigated. References (1) Téblick A. et al. Critical Care 2021. (2) Téblick A. et al. Endocrinology 2022. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Saturday, June 11, 2022 1:42 p.m. - 1:47 p.m.

Single-cell transcriptome analysis identifies a unique tumor cell type producing multiple hormones in ectopic ACTH and CRH secreting pheochromocytoma.

Ectopic Cushing's syndrome due to ectopic ACTH&CRH-secreting by pheochromocytoma is extremely rare and can be fatal if not properly diagnosed. It remains unclear whether a unique cell type is responsible for multiple hormones secreting. In this work, we performed single-cell RNA sequencing to three different anatomic tumor tissues and one peritumoral tissue based on a rare case with ectopic ACTH&CRH-secreting pheochromocytoma. And in addition to that, three adrenal tumor specimens from common pheochromocytoma and adrenocortical adenomas were also involved in the comparison of tumor cellular heterogeneity. A total of 16 cell types in the tumor microenvironment were identified by unbiased cell clustering of single-cell transcriptomic profiles from all specimens. Notably, we identified a novel multi-functionally chromaffin-like cell type with high expression of both POMC (the precursor of ACTH) and CRH, called ACTH+&CRH + pheochromocyte. We hypothesized that the molecular mechanism of the rare case harbor Cushing's syndrome is due to the identified novel tumor cell type, that is, the secretion of ACTH had a direct effect on the adrenal gland to produce cortisol, while the secretion of CRH can indirectly stimulate the secretion of ACTH from the anterior pituitary. Besides, a new potential marker (GAL) co-expressed with ACTH and CRH might be involved in the regulation of ACTH secretion. The immunohistochemistry results confirmed its multi-functionally chromaffin-like properties with positive staining for CRH, POMC, ACTH, GAL, TH, and CgA. Our findings also proved to some extent the heterogeneity of endothelial and immune microenvironment in different adrenal tumor subtypes.

MON-309 Prevalence of Silent Corticotroph Adenomas in a Large Cohort of Nonfunctioning Pituitary Adenomas: Plasma Proopiomelanocortin(POMC) Levels and Response to Pasireotide LAR

Silent corticotroph adenomas (SCAs) are tumors of the TPIT anterior pituitary cell lineage that do not lead to biochemical or clinical Cushings syndrome. Thus, they present as clinically nonfunctioning pituitary adenomas (CNFPAs) and are only diagnosed pathologically. Since they are often aggressive tumors, identification of a peripheral blood marker of SCA activity would be useful for diagnosis and monitoring. Some data suggest that aberrant processing of POMC, the precursor of ACTH, underlies the lack of elevated biologically active ACTH and thus cortisol excess in SCAs. We hypothesized that these tumors could secrete POMC, resulting in elevated plasma levels of POMC in patients with SCAs. Therefore, we investigated plasma POMC levels as a potential marker of this tumor type and correlated with tumor ACTH immunoreactivity (IR), which may be detecting unprocessed POMC. We studied 267 patients (134M, 133F, age 56.3±13.6yr) with CNFPAs (Cushings excluded) prior to surgery and at enrollment in a prospective, observational study. We also studied 9 patients with known SCAs with residual macroadenomas after surgery. Peripheral blood was sampled for POMC, ACTH and cortisol levels. POMC was measured by in-house two-site ELISA (detects POMC and 22kD pro-ACTH) and ACTH and cortisol by Immulite(Siemens). POMC levels were compared to the 95%CI of the mean of 70 healthy subjects and considered elevated if ≥ the 97.5 percentile of 39 fmol/mL. Of the CNFPA cohort, 12/267 had elevated POMC levels (range 39-166 fmol/mL) and 4 of the 12 had elevated ACTH levels (> 50 pg/ml)(range 53.6-76 pg/ml). Of the 12 with elevated POMC, 9 underwent surgery and 6 of them had positive ACTH IR in their tumors. An additional 13 patients in the CNFPA cohort had weak ACTH IR tumors, but POMC <39 fmol/mL and normal ACTH. POMC levels were elevated in all 9 known SCA patients (range 40-996 fmol/mL), being highest in those with the most aggressive tumors. ACTH levels were elevated in 6 of them (range 50.6-397 pg/ml). POMC levels were lowered with surgery in 4 of 4 SCA patients followed longitudinally. Two SCAs were treated with monthly pasireotide LAR (40 mg escalated to 60 mg) for 8 months. Plasma POMC levels fell from 104 to 21 fmol/mL in 1 patient, but did not change in the 2nd, 124 to 112 fmol/mL. Both patients had no change in the size of their macroadenomas during treatment. In summary, patients with elevated plasma POMC levels were correctly identified as SCAs in most surgically treated patients and POMC levels were lowered by tumor removal in all who were tested longitudinally. Although POMC levels were not elevated in some other patients with weakly positive ACTH IR tumors, further characterization of these tumors by lineage specific transcription factors is underway to confirm them to be of corticotroph cell origin. These data suggest that plasma POMC measurements may have clinical utility in the evaluation of SCAs and this warrants further study.

OR19-06 Sepsis-Induced Critical Illness in Mice Alters Key Regulators of ACTH Production and Secretion Within the Anterior Pituitary Gland

IntroductionCritical illness is hallmarked by high plasma cortisol without elevated ACTH. This is partly explained by low cortisol-binding proteins and reduced binding affinity and by suppressed cortisol metabolism, 3 peripheral drivers of increased free cortisol (corticosterone (CORT) in rodents).1 We hypothesized that lack of elevated plasma ACTH is explained by CORT-induced feed-back inhibition either due to suppressed CRH or AVP pituitary signaling or to direct glucocorticoid receptor (GR)-mediated action within corticotrophs. To test this hypothesis, we documented alterations in ACTH precursors and key enzymes controlling ACTH maturation and secretion in a mouse model of sepsis-induced critical illness.MethodsC57Bl/6 mice were randomly allocated to a healthy control group or to 4 critically ill groups sacrificed after increasing illness duration (30 hours (H), 3 days (D), 5D or 7D). Critical illness was induced by sepsis brought about by cecal-ligation and puncture followed by fluid-resuscitation and antibiotics treatment. The study was continued until 15 surviving animals per time cohort were reached (n=120).We quantified pituitary pro-opiomelanocortin (POMC) gene/protein expression and POMC plasma concentrations, pituitary POMC intracellular trafficking and cleavage via intracellular POMC sorting/trafficking receptor Carboxypeptidase E (CPE) and prohormone convertase 1 (PC1/3) gene/protein expression. Gene expression of Annexin A1, an inhibitor of mature ACTH secretion, was quantified as marker of GR-mediated CORT-induced feedback inhibition at corticotroph level.ResultsPlasma CORT concentrations were median 3-fold increased during critical illness (p<0.001 for all time cohorts) in the face of normal (for 30H, 3D and 5D cohorts) to low (7D time cohort; p=0.01) plasma ACTH concentrations. Plasma POMC concentrations were higher in critically ill than in control mice (p=0.05). POMC gene expression (but not protein, P=0.8) was a median 55% higher in critically ill mice than in controls (p<0.05 for all time cohorts). In contrast, pituitary mature ACTH protein concentration was median 61% lower in critically ill than in control mice (p<0.01). CPE gene expression was only increased in 30H time cohort (p<0.001). PC1/3 gene and protein expression were positively correlated (R2 0.1; p=0.001) and were reduced (by 37% and 43%, respectively) during the entire course of critical illness (p<0.01). Annexin A1 gene expression was increased during critical illness (p<0.05 for all time cohorts).ConclusionSuppressed CRH or AVP signaling and GR-mediated action within corticotrophs explained lack of elevated plasma ACTH in critical illness, as indicated by impaired POMC processing and ACTH maturation. However, increased POMC gene expression suggests ongoing corticotroph activation, the driver of which needs to be identified. 1. Teblick A et al. Nat Rev Endocrinol 2019

SUN-291 Presence of Aberrant Adrenocorticotropic Hormone Precursors in Two Cases of McCune- Albright Syndrome

Background: McCune-Albright syndrome (MAS) is a rare disorder. MAS is caused by an activating postzygotic somatic mutation in the GNAS, and, is classically defined by the occurrence of fibrous dysplasia (FD), café-au-lait skin macules, and precocious puberty. Autonomous GH and/or PRL production in MAS has been reported. However, there have been no reports of ACTH excess in MAS. Method: Plasma ACTH and serum cortisol (F) levels were assessed using electrochemiluminescence immunoassays (Eclusys ACTHTM and Eclusys Cortisol IITM, respectively; Roche Diagnostics K.K., Tokyo, Japan).Clinical Cases: Case1; 42-year-old man showed craniofacial deformities and suffered from multiple bone fractures. He was diagnosed with FD at the age of 23 years. Café-au-lait macules were found on his back. He had slightly acromegaloid features. He showed no cushingoid features. Pituitary adenoma or hyperplasia was not detected by MRI. The diagnosis of GH excess was confirmed by no suppression of serum GH levels by a 75-g oral glucose tolerance test (nadir GH: 2.34 ng/mL) and an elevated serum IGF-I level (307 ng/mL; normal range: 92-257 ng/mL). The patient was treated with monthly subcutaneous lanreotide injection and then GH excess was well controlled. Basal ACTH and F levels in blood were 40.6-63.4 pg/mL and 8.0-10.5 μg/dL, respectively. The urinary free cortisol (UFC) level was 53 μg/day. Autonomous F excess was excluded by the level of midnight F (1.2 μg/dL) and the level of F (0.2 μg/dL) after a low-dose (1 mg) dexamethasone suppression test (DST). Case2; A 32-year-old man was diagnosed with MAS and gigantism at the Pediatrics Department at the age of 5 years. Treatment of GH excess was well controlled by monthly octreotide depot. He had no acromegaloid features and no cushingoid features. Café-au-lait macules were observed from the left flank to the back. Pituitary adenoma or hyperplasia was not detected by MRI. Basal ACTH and F levels in blood were 35.5-73.1 pg/mL and 7.0-11.7 μg/dL, respectively. The UFC level was 61 μg/day. Autonomous F excess was excluded by the level of F (<0.2 μg/dL) after a low-dose (0.5 mg) DST.Possibility of primary adrenal insufficiency was excluded by ACTH stimulation test and/or insulin tolerance test in both cases. The involvement of 11β-HSD1 by GH excess and PC1/3 deficiency were also excluded. Gel exclusion chromatography was then performed. POMC and pro-ACTH were detected and the aberrant ACTH/normal ACTH ratio was 42% in both cases. Conclusion: This is the first report of the presence of aberrant ACTH precursors, particularly POMC, in MAS. A high ratio of circulating ACTH to F may suggest secretion of inactive ACTH precursors in MAS. Further investigations are required to determine whether GNAS mutations or other mechanisms are involved in the presence of aberrant ACTH precursors in MAS.

Pituitary carcinoma with hepatic metastasis hypersecreting ACTH precursors masquerading as Nelson syndrome after bilateral adrenalectomy for refractory Cushing's syndrome

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Crosstalk of BMP-4 and RA signaling pathways on Pomc gene regulation in corticotrophs.

Retinoic acid (RA), an active metabolite of Vitamin A, and bone morphogenetic protein 4 (BMP-4) pathways control the transcription of pro-opiomelanocortin (Pomc), the precursor of ACTH. We describe a novel mechanism by which RA and BMP-4 act together in the context of pituitary corticotroph tumoral cells to regulate Pomc transcription. BMP-4 and RA exert a potentiated inhibition on Pomc gene expression. This potentiation of the inhibitory action on Pomc transcription was blocked by the inhibitory SMADs of the BMP-4 pathway (SMAD6 and SMAD7), a negative regulator of BMP-4 signaling (TOB1) and a blocker of RA pathway (COUP-TFI). AtT-20 corticotrophinoma cells express RA receptors (RARB, RXRA and RXRG) which associate with factors of BMP-4 (SMAD4 and SMAD1) signaling cascade in transcriptional complexes that block Pomc transcription. COUP-TFI and TOB1 disrupt these complexes. Deletions and mutations of the Pomc promoter and a specific DNA-binding assay show that the complexes bind to the RARE site in the Pomc promoter. The enhanced inhibitory interaction between RA and BMP-4 pathways occurs also in another relevant corticotroph gene promoter, the corticotropin-releasing hormone receptor 1 (Crh-r1). The understanding of the molecules that participate in the control of corticotroph gene expression contribute to define more precise targets for the treatment of corticotrophinomas.

Identification of recurrent USP48 and BRAF mutations in Cushing’s disease

Cushing’s disease results from corticotroph adenomas of the pituitary that hypersecrete adrenocorticotropin (ACTH), leading to excess glucocorticoid and hypercortisolism. Mutations of the deubiquitinase gene USP8 occur in 35–62% of corticotroph adenomas. However, the major driver mutations in USP8 wild-type tumors remain elusive. Here, we report recurrent mutations in the deubiquitinase gene USP48 (predominantly encoding p.M415I or p.M415V; 21/91 subjects) and BRAF (encoding p.V600E; 15/91 subjects) in corticotroph adenomas with wild-type USP8. Similar to USP8 mutants, both USP48 and BRAF mutants enhance the promoter activity and transcription of the gene encoding proopiomelanocortin (POMC), which is the precursor of ACTH, providing a potential mechanism for ACTH overproduction in corticotroph adenomas. Moreover, primary corticotroph tumor cells harboring BRAF V600E are sensitive to the BRAF inhibitor vemurafenib. Our study thus contributes to the understanding of the molecular mechanism of the pathogenesis of corticotroph adenoma and informs therapeutic targets for this disease.

Proopiomelanocortin processing and prohormone convertase 1 level in dogs with pituitary corticotroph tumors

Preliminary data suggest that prohormone convertase 1 (PC1/3) protein expression and proopiomelanocortin (POMC) processing are altered in large corticotroph tumors. The aim of this study was to characterize the levels of ACTH precursors and PC1/3 protein in small and large corticotroph tumors of dogs with Cushing's disease. Pituitary tumors of dogs with Cushing's disease were collected postmortem 30 min to 12h after natural death or euthanasia, and classified as small or large. POMC, pro-ACTH, and PC1/3 were detected by Western blotting. Five small and 6 large corticotroph tumors were collected. POMC and pro-ACTH signals were visualized in 5/6 large tumors and in 4/5 small tumors. The strongest signal intensity was observed in 2 large tumors. The PC1/3 signal was weak to undetectable in 6/6 large tumors but strong in 5/5 small tumors. These results suggest differences in PC1/3 protein levels and patterns of POMC processing between large and small corticotroph tumors. If confirmed in larger groups of tumors, further studies will be required to characterize the mechanism involved in these differences.

Proopiomelanocortin interference in the measurement of adrenocorticotrophic hormone: a United Kingdom National External Quality Assessment Service study.

It is recognized that measurement of ACTH-precursor peptides including proopiomelanocortin (POMC) has clinical utility in identifying the aetiology of Cushing's syndrome. Recent data have also demonstrated cross-reactivity of POMC in ACTH immunoassays used in clinical laboratories. The aim of this study was to assess the cross-reactivity of POMC in the main commercial immunoassays for ACTH and to survey the awareness of laboratory professionals to this potential interference. To assess cross-reactivity, specimens containing ACTH and/or POMC were prepared by the UK National External Quality Assessment Service (UK NEQAS) [Edinburgh]. A separate interpretative exercise was also sent to participating laboratories. Eighty-seven laboratories measured 'total' ACTH (i.e. ACTH and/or POMC) in their assays. Cross-reactivity of POMC varied from a mean of 1·6-4·7% (reflected in a large percentage increase in measured ACTH of up to 261% due to POMC cross-reactivity) depending on the manufacturer. Major differences in the clinical interpretation of test results were observed in returned responses to the interpretative exercise. An appraisal of POMC cross-reactivity in currently available ACTH immunoassays has been achieved. Cross-reactivity was sufficient to detect ACTH precursors at concentrations that could be found in patients with ectopic ACTH syndrome. These data will assist laboratories in interpreting results when assessing the hypothalamic-pituitary-adrenal axis. Endocrinologists and laboratory professionals should be aware of the degree of cross-reactivity in ACTH immunoassay in order to minimize the risk of misinterpretation of results and/or potentially delayed treatment.

Clinical Utility of Plasma POMC and AgRP Measurements in the Differential Diagnosis of ACTH-Dependent Cushing's Syndrome

Distinguishing between pituitary [Cushing's disease (CD)] and ectopic causes [ectopic ACTH syndrome (EAS)] of ACTH-dependent Cushing's syndrome can be challenging. Inferior petrosal sinus sampling (IPSS) best discriminates between CD and occult EAS but is a specialized procedure that is not widely available. Identifying adjunctive diagnostic tests may prove useful. In EAS, abnormal processing of the ACTH precursor proopiomelanocortin (POMC) and the accumulation of POMC-derived peptides might be expected and abnormal levels of other neuropeptides may be detected. The objective of the study was to evaluate the diagnostic utility of POMC measurements for distinguishing between CD and occult EAS in patients referred for IPSS. Another objective of the study was to evaluate in parallel the diagnostic utility of another neuropeptide, agouti-related protein (AgRP), because we have observed a 10-fold elevation of AgRP in plasma in a patient with EAS from small-cell lung cancer. Plasma POMC and AgRP were measured in 38 Cushing's syndrome patients presenting for IPSS, with either no pituitary lesion or a microadenoma on magnetic resonance imaging, and in 38 healthy controls. Twenty-seven of 38 patients had CD; 11 of 38 had EAS. The mean POMC was higher in EAS vs CD [54.5 ± 13.0 (SEM) vs 17.2 ± 1.5 fmol/mL; P < .05]. Mean AgRP was higher in EAS vs CD (280 ± 76 vs 120 ± 16 pg/mL; P = .01). Although there was an overlap in POMC and AgRP levels between the groups, the POMC levels greater than 36 fmol/mL (n = 7) and AgRP levels greater than 280 pg/mL (n = 3) were specific for EAS. When used together, POMC greater than 36 fmol/mL and/or AgRP greater than 280 pg/mL detected 9 of 11 cases of EAS, indicating that elevations in these peptides have a high positive predictive value for occult EAS. Expanding upon previous observations of high POMC in EAS, this study specifically demonstrates elevated POMC levels can identify occult ectopic tumors. Elevations in AgRP also favor the diagnosis of EAS, suggesting AgRP should be further evaluated as a potential neuroendocrine tumor marker.

Activation of the dopamine receptor type-2 (DRD2) promoter by 9-cis retinoic acid in a cellular model of Cushing's disease mediates the inhibition of cell proliferation and ACTH secretion without a complete corticotroph-to-melanotroph transdifferentiation.

Cushing's disease (CD) is a rare condition in which hypercortisolemia is secondary to excessive ACTH release from a pituitary corticotroph adenoma. CD is associated with significant morbidity and mortality, and a safe therapy that effectively targets the pituitary tumor is still lacking. Retinoic acid (RA) and dopamine agonists (DAs) have recently been considered as monotherapy in CD patients, and satisfactory results have been reported, albeit in a limited number of patients. Given the permissive role of RA on the dopamine receptor type-2 (DRD2), the aim of the present study was to see whether a combination of 9-cis RA and the DA bromocriptine (Br) might represent a possible treatment for CD. Here we show that 9-cis RA induces a functional DRD2 in the pituitary corticotroph cell line AtT20, and increases cell sensitivity to Br via a mechanism only partially related to corticotroph-to-melanotroph transdifferentiation. In addition, 9-cis RA and Br act synergistically to modulate cell viability, with favorable implications for clinical use. In nearly 45% of corticotropinoma-derived primary cultures, the combined administration of 9-cis RA and Br lowered the steady-state level of the ACTH precursor proopiomelanocortin (POMC) more efficiently than either of the drugs alone. In conclusion, the effects of a combination of 9-cis RA and Br on ACTH synthesis/secretion and cell viability in AtT20, and on POMC transcriptional activity in human corticotropinomas might represent a suitable starting point for assessing the potential of this treatment regimen for ACTH-secreting pituitary adenomas. This study thus has potentially important implications for novel therapeutic approaches to CD.

Safety, efficacy and weight effect of two 11β‐HSD1 inhibitors in metformin‐treated patients with type 2 diabetes

We assessed safety and efficacy of two selective 11β-HSD1 inhibitors (RO5093151/RO-151 and RO5027383/RO-838) in this randomized, controlled study in metformin-treated patients with type 2 diabetes. Patients either received placebo (N = 21), RO-151 BID 5 mg (N = 24) or 200 mg (N = 20) or RO-838 QD 50 mg (N = 21) or 200 mg (N = 24) for 28 days. Metabolic assessments comprising of nine-point plasma glucose profiles, oral glucose tolerance tests and determination of metabolic biomarkers including insulin, C-peptide, glucagon, HbA1c and lipids were done at baseline and end of treatment. Despite the short treatment duration, both RO-151 and RO-838 showed trends for improved HbA1c and consistent reductions in body weight (-0.86 to -1.67 kg) exceeding those observed with placebo (-0.28 kg, p = 0.019 for 200 mg RO-151 vs. placebo). Insulin sensitivity parameters (e.g. HOMA-IR and Matsuda-Index) improved non-significantly with 200 mg RO-151. Lipid parameters did not consistently improve with either compound, but RO-838 led to non-significant increases in triglycerides and VLDL-cholesterol versus placebo. Both compounds were well tolerated and showed inhibitory effects on 11β-HSD1 activity based on urinary corticosteroid excretion. As reported for other 11β-HSD1-inhibitors increased concentrations of ACTH and adrenal androgen precursors were found with RO-151, but not with RO-838. Slight metabolic improvements were seen, in particular with RO-151 high dose, however, the observed changes often did not reach statistical significance and were not clearly dose dependent. Studies of longer duration are needed to further investigate potential benefits and risks of these compounds.

Recurrent Pituitary Macroadenoma with Increased Plasma ACTH Precursors that Cross-React in a Commonly Used ACTH Immunoassay

adrenocorticotropic hormone

A Novel Medical Treatment of Cushing's Due to Ectopic ACTH in a Patient With Neurofibromatosis Type 1

A 64-year-old male presented with neurofibromatosis 1 and Cushing’s syndrome. Clinically he was over weight, depressed with extensive skin bruising and hypertension. His 24 hours urinary metanephrines, urinary 5HIAA, gut peptides and chromgranin levels were normal. His renal function and renal MRI scan was also normal. His cortisol failed to suppress on overnight dexamethsone suppression test. His low dose dexamethasone suppression with CRH stimulation showed failure of suppression of cortisol to < 50 nmol/L and ACTH was measurable at 10 ng/L on day 3. There was no response of ACTH or cortisol to CRH stimulation. His ACTH precursors were high at 126 pmol/L consistent with defective pro-opiomelanocortin (POMC) processing suggesting an ectopic source of ACTH production. The MRI scan of his pituitary and CT scan of the adrenal glands was normal. His octreotide scan was negative. The source of his ectopic ACTH was most likely a large retroperitoneal plexiform neurofibroma seen on CT abdomen that had undergone malignant peripheral nerve sheath tumour transformation on histology. He was a poor surgical risk for tumour debulking procedure. In view of the available literature and role of c-kit signalling in neurofibromatosis, he was treated with Imitinib. Four months after the treatment his Cushings had resolved on biochemical testing. After a year his plexiform neurofibroma has not increased in size. To our knowledge, this is the first case of NF1 associated with clinical and biochemical features of Cushing’s secondary to ectopic ACTH due to MPNST in a plexiform neurofibroma and its resolution on treatment with imatinib.

PlasmaACTHPrecursors in Cats with Pituitary‐Dependent Hyperadrenocorticism

Diagnosis of pituitary-dependent hyperadrenocorticism (PDH) in cats is challenging because there is no specific diagnostic test. The determination of plasma ACTH precursor (POMC and pro-ACTH) concentration might facilitate the diagnosis of PDH in cats. The aim of the study was to evaluate prospectively the plasma concentrations of ACTH precursors in a small cohort of cats with PDH and to estimate the value of this approach for diagnosis. Four groups of cats were included: group 1 (cats with PDH), group 2 (cats with diabetes mellitus but not hyperadrenocorticism (HAC)), group 3 (cats with diabetes mellitus and confirmed acromegaly but not HAC), and group 4 (healthy cats). PDH diagnosis was based on clinical data, low-dose dexamethasone suppression test (LDDST), and adrenal and pituitary gland computed tomography (CT) scan. For groups 2, 3, and 4, hyperadrenocorticism was excluded by LDDST or urine cortisol:creatinine ratio (UCCR). An immunoluminometric assay was used to determine plasma concentrations of ACTH precursors in the 4 groups of cats. Group 1 contained 9 cats (enlarged pituitary gland in 7/9). Plasma ACTH precursor concentrations ranged from <53 to >1010 pmol/L with 8/9 concentrations ≥ 229 pmol/L. Groups 2, 3, and 4 included 13, 7, and 13 cats, respectively. Plasma ACTH precursor concentrations ranged from <53 to 96 pmol/L in group 2, <53 to 72 pmol/L in group 3, and <53 to 99 pmol/L in group 4. High plasma concentration of ACTH precursors in cats (>100 pmol/L) is highly suggestive of PDH.

Testosterone modulates pituitary vasotocin receptor expression and adrenal activity in osmotically stressed chicken

Regulation of arginine vasotocin (AVT), avian neurohypophyseal hormone, is an important component of the hypothalamo-pituitary–adrenal axis. Changes in plasma osmolality levels and sex steroids are known to affect AVT gene expression. The present study reports the effect of water deprivation and testosterone treatment independently, as well as simultaneously, on the pituitary vasotocin receptor VT2R expression and adrenal steroidogenic activity in sexually immature male chicken ( Gallus gallus). Birds were divided into four groups— control, water deprived (WD), testosterone injected (TE) and TE treated water deprived (TE + WD). WD decreased and TE treatment alone or in combination with WD (TE + WD) increased VT2R expression compared to the control. Expression of pro-opiomelanocortin (POMC) was also studied since this gene is a polypeptide precursor of ACTH and is under the negative feedback of adrenal corticoids. TE treatment as well as WD separately or when coupled together decreased the POMC mRNA expression in the pituitary but stimulated adrenal steroidogenic activity. Further, VT2R expression decreased in TE + WD compared to TE group, but it was not different from the vehicle treated control group suggesting that the suppressive effect of WD on VT2R expression was inhibited by the stimulatory effect of testosterone. Similarly, although both TE and WD decreased POMC expression and increased steroidogenic activity, no further decrease or increase in these parameters was observed when these two (WD and TE) treatments were combined together. Although, the exact mechanism is not clear, data indicate a stimulatory action of testosterone on VT2R expression and adrenal function despite a decreased expression of POMC mRNA. Results also suggest that testosterone treatment to sexually immature birds, in addition to its effect on hypothalamic AVT neurons (earlier study) and pituitary VT2R expression (present study), masks or inhibits osmotic stress-induced alterations in pituitary–adrenal activity.

Glucocorticoid receptor over-expression promotes human small cell lung cancer apoptosis in vivo and thereby slows tumor growth.

Small cell lung cancer (SCLC) is an aggressive tumor, associated with ectopic ACTH syndrome. We have shown that SCLC cells are glucocorticoid receptor (GR) deficient, and that restoration of GR expression confers glucocorticoid sensitivity and induces apoptosis in vitro. To determine the effects of GR expression in vivo, we characterized a mouse SCLC xenograft model that secretes ACTH precursor peptides, and so drives high circulating corticosterone concentrations (analogous to the ectopic ACTH syndrome). Infection of SCLC xenografts with GR-expressing adenovirus significantly slowed tumor growth compared with control virus infection. Time to fourfold initial tumor volume increased from a median of 9 days to 16 days (P=0.05; n=7 per group). Post-mortem analysis of GR-expressing tumors revealed a threefold increase in apoptotic (TUNEL positive) cells (P<0.01). Infection with the GR-expressing adenovirus caused a significant reduction in Bcl-2 and Bcl-xL transcripts. Furthermore, in both the GR-expressing adenovirus-infected cells and tumors, a significant number of uninfected cells underwent apoptosis, supporting a bystander cell killing effect. Therefore, GR expression is pro-apoptotic for human SCLCs in vivo, as well as in vitro, suggesting that loss of GR confers a survival advantage to SCLCs.

Processing of high-molecular-weight form adrenocorticotropin in human adrenocorticotropin-secreting tumor cell line (DMS-79) after transfection of prohormone convertase 1/3 gene

Ectopic ACTH-producing tumors preferentially secrete biologically inactive ACTH precursors and ACTH-related fragments. DMS-79 is known to secrete unprocessed high-molecular-weight (HMW) form ACTH. To determine whether prohormone convertase (PC) 1/3 is involved in the abnormal processing of proopiomelanocortin (POMC), we studied whether PC1/3 and 2 genes are expressed in DMS-79, and whether overexpression of PC1/3 gene affects POMC processing pattern. Steady-state mRNA levels of PC1/3 and 2 were determined by real-time RT-PCR. Molecular weights of ACTH-related peptides were determined by chromatographical analyses coupled with ACTH and beta-endorphin (beta-END) radioimmunoassays. PC1/3 gene was transfected into DMS-79 by retrovirus transduction using pMX-IP vector encoding PC1/3 cDNA. The steady-state mRNA levels of PC1/3 and 2 in DMS-79 were lower than those in ACTH-secreting and nonfunctioning pituitary tumors. DMS-79 predominantly secreted HMW form with both ACTH and beta-END immunoreactivities by size-exclusion chromatography. After purification by immunoaffinity chromatography with anti-ACTH antibody, the apparent molecular weight of HMW form ACTH was estimated to be 16 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with silver staining. After retroviral transfection of PC1/3 cDNA into DMS-79 and puromycin selection, PC1/3 stably-expressing cell line (DMS-79T) secreted two immunoreactive ACTH components, a major one coeluting with ACTH(1-39) and a minor one as a HMW form as well as two beta- END immunoreactive components coeluting with beta-lipotropic hormone and beta-END, respectively. Thus, we have established PC1/3 stably-expressing cell line (DMS-79T) capable of proteolytically processing ACTH precursor molecule(s) into mature ACTH and beta-END.

Long-term hypoxia enhances ACTH response to arginine vasopressin but not corticotropin-releasing hormone in the near-term ovine fetus

This study tested the hypothesis that long-term hypoxia (LTH) results in enhanced fetal corticotrope sensitivity to the ACTH secretagogues, corticotropin-releasing hormone (CRH), and AVP. Ewes were maintained at high altitude (3,820 m) from 40 to 130-131 days of gestation. Upon return to the laboratory, hypoxia was maintained by maternal nitrogen infusion. Vascular catheters were placed in both LTH (n = 4) and normoxic controls (n = 4). Each fetus received a 15-min infusion of either saline, 100 ng/kg of ovine CRH, or 20 ng/kg of AVP/min over 3 consecutive days in a randomized order. Fetal blood samples were collected at 0, 15, 30, 60, and 90 min after the start of infusion and analyzed for ACTH(1-39), ACTH precursors, and cortisol. Anterior pituitaries were collected from additional noninstrumented fetuses for analysis of vasopressin receptor 1b (V1b) mRNA and protein. Basal plasma concentrations of both ACTH(1-39) and ACTH precursors were higher in LTH fetuses and were not altered by saline infusion. In response to CRH, ACTH(1-39) increased in both groups and was higher in the LTH group compared with control (P < 0.05). When analyzed as sum of ACTH(1-39) released (Delta0-90 min) above basal, CRH released equal amounts of ACTH(1-39) in both groups. In LTH fetuses, AVP evoked a greater ACTH(1-39) release (P < 0.05) when analyzed as an increased sum of ACTH(1-39) (Delta0-90 min) above basal. Both CRH and AVP elicited a release of ACTH precursors with no differences observed between LTH and control. AVP and CRH elicited significant increases in cortisol, which were higher in response to AVP than CRH. V1b mRNA and protein were elevated in the anterior pituitary of LTH fetuses compared with control. LTH significantly increases pituitary sensitivity to AVP. This enhanced sensitivity may be a mechanism of our previously observed enhanced corticotrope function.