GH Assay Research Articles

Revisiting the usefulness of the short acute octreotide test to predict treatment outcomes in acromegaly.

We previously described that a short version of the acute octreotide test (sAOT) can predict the response to first-generation somatostatin receptor ligands (SRLs) in patients with acromegaly. We have prospectively reassessed the sAOT in patients from the ACROFAST study using current ultra-sensitive GH assays. We also studied the correlation of sAOT with tumor expression of E-cadherin and somatostatin receptor 2 (SSTR2) . A total of 47 patients treated with SRLs for 6 months were evaluated with the sAOT at diagnosis and correlated with SRLs' response. Those patients whose IGF1 decreased to <3SDS from normal value were considered responders and those whose IGF1 was ≥3SDS, were considered non-responders. The 2 hours GH value (GH2h) after s.c. administration of 100 mcg of octreotide was used to define predictive cutoffs. E-cadherin and SSTR2 immunostaining in somatotropinoma tissue were investigated in 24/47 and 18/47 patients, respectively. In all, 30 patients were responders and 17 were non-responders. GH2h was 0.68 (0.25-1.98) ng/mL in responders vs 2.35 (1.59-9.37) ng/mL in non-responders (p<0.001). GH2h = 1.4ng/mL showed the highest ability to identify responders (accuracy of 81%, sensitivity of 73.3%, and specificity of 94.1%). GH2h = 4.3ng/mL was the best cutoff for non-response prediction (accuracy of 74%, sensitivity of 35.3%, and specificity of 96.7%). Patients with E-cadherin-positive tumors showed a lower GH2h than those with E-cadherin-negative tumors [0.9 (0.3-2.1) vs 3.3 (1.5-12.1) ng/mL; p<0.01], and patients with positive E-cadherin presented a higher score of SSTR2 (7.5 ± 4.2 vs 3.3 ± 2.1; p=0.01). The sAOT is a good predictor tool for assessing response to SRLs and correlates with tumor E-cadherin and SSTR2 expression. Thus, it can be useful in clinical practice for therapeutic decision-making in patients with acromegaly.

FRI206 A Rare Case Of Coexisting Acromegaly And Adrenal Cushing’s Syndrome

Abstract Disclosure: T. Chamakkala: None. T. Gallagher: None. Introduction: Acromegaly has been associated with higher risk of cancer morbidity and mortality. Acromegaly coexisting with adrenal Cushing’s disease has been rarely described in literature. We present a patient who was found to have acromegaly during evaluation for Cushing’s syndrome. Clinical Case: A 50-year-old woman presented to the office for endocrinology evaluation at the referral of PCP for elevated 24h urine cortisol level 176ug/24h. She had noticed facial plethora over several years, fatigue, and easy bruising. She had recently been diagnosed with hypertension, poorly controlled on two medications at the time of evaluation. Repeat 24h urine cortisol and midnight salivary cortisol levels were elevated; dexamethasone suppression test was positive. ACTH was &amp;lt;1.5pg/mL, consistent with ACTH independent hypercortisolemia. Adrenal CT showed 2.6x3cm left adrenal adenoma. She underwent left adrenalectomy and pathology showed adrenal cortical adenoma. During evaluation for Cushing’s disease and new onset hypertension, IGF1 was evaluated and found to be elevated at 354ng/mL. She additionally endorsed symptoms of worsening carpal tunnel syndrome and increasing ring size. After adrenalectomy, IGF1 was repeated and remained elevated at 429ng/mL. Growth hormone suppression test showed nadir of 0.56ng/mL which is higher than &amp;lt;0.3ng/mL expected of high sensitivity GH assays. Pituitary MRI showed three suspected pituitary microadenomas, 4mm and 5mm in left gland, 7mm in right gland. Given difficulty with surgical approach and higher risk of hypopituitarism, she was started on lanreotide for treatment without surgery. She underwent genetic counseling and was offered genetic testing. Conclusion: This case highlights the rare coexistence of acromegaly and adrenal Cushing’s disease in a 50 year old woman. Though the relationship between acromegaly and cancer has been historically controversial, more recent studies have shown an increased risk of both benign and malignant tumors with acromegaly. Untreated Cushing’s Disease has been associated with mildly elevated IGF1 which then decreases after remission; it is unclear if the same pathological process is involved in other etiologies of hypercortisolemia like adrenal Cushing’s syndrome, but re-evaluation of IGF1 after treatment of Cushing’s should be considered. As Cushing’s and acromegaly share similar consequences such as worsening HTN, changing facial appearance, and worsening diabetes, it is prudent to consider each as differential diagnoses when signs do not remit after treatment. Acromegaly has additionally been associated with other endocrinopathies in syndromes including MEN1 syndrome, McCune Albright Syndrome, and Carney Complex. Evaluation for these syndromes and consideration for genetic testing should be considered in the evaluation of a patient with acromegaly and additional associated endocrinopathies. Presentation: Friday, June 16, 2023

Standardization of Growth Hormone and Insulin-like Growth Factor-I Measurement.

Determination of serum levels of GH and IGF-I is crucial for the diagnosis and treatment of GH deficiency and disorders related to GH excess such as acromegaly and pituitary gigantism. However, significant discrepancies in measured GH values among the methods were observed around the world. In Japan, the Study Committee for GH and Its Related Factors of The Foundation for Growth Science standardized GH values measured with various commercially available GH assay kits by creating formulas to adjust them to their averages. The committee also established reference values for IGF-I in Japanese subjects at all ages from childhood to adulthood. Internationally, collaborators have been working on the harmonization of GH measurements.

Gender has to be taken into account in diagnosing adult growth hormone deficiency by the GHRH plus arginine test

ObjectiveData on the effect of gender on the interpretation of the GHRH plus arginine stimulation test (GHRH+ARG test) is controversial. We validated the GHRH+ARG stimulation test in control subjects and patients with organic or idiopathic pituitary disease and a suspicion of adult growth hormone deficiency (AGHD) using the Immulite 2000 XPi GH assay. DesignWe studied 126 apparently healthy adults (median age 38.8years) and 34 patients with a suspicion of AGHD (median age 42.2years). Identification of AGHD with the GHRH+ARG test was investigated with commonly accepted BMI-related consensus cut-off limits for peak GH concentrations. Serum samples collected during the GHRH+ARG test were analysed for GH in 2014–2015. Serum IGF-1 concentrations were studied as a reference. ResultsIn 14 of 65 (22%) control males the GH peak value was below the BMI-related cut-off limits for GH sufficiency indicating a false diagnosis of AGHD. All control females had a normal GHRH+ARG response. Median peak GH response was significantly (p<0.001) higher in female (39.3μg/L) than in male controls (21μg/L). According to consensus cut-offs all but one young female patient had a deficient response compatible with a diagnosis of AGHD. ConclusionsThe GH response to stimulation by GHRH+ARG is gender-dependent, being lower in healthy males than in females. Gender should be considered when defining cut-off limits for peak GH concentrations in the GHRH+ARG test. The presently used BMI-related cut-off levels will lead to a significant misclassification of males as GH deficient.

MANAGEMENT OF ENDOCRINE DISEASE: Acromegaly and pregnancy: a contemporary review.

Although fertility is frequently impaired in women with acromegaly, pregnancy is apparently becoming more common due to improvement in acromegaly treatment as well as in fertility therapy. As a result, several studies on pregnancy in patients with acromegaly have been published in recent years adding new and relevant information to the preexisting literature. Also, new GH assays with selective specificities and the knowledge of the expression of the various GH genes have allowed a better understanding of somatotrophic axis function during pregnancy. In this review, we show that pregnancy in women with acromegaly is generally safe, usually with tumoral and hormonal stability. Although the paucity of data limits evidence-based recommendations for preconception counseling and pregnancy surveillance, controlling tumor size and hormonal activity before pregnancy is highly recommended to ensure better outcomes, and surgical control should be attempted when feasible. Treatment interruption at pregnancy confirmation has also proven to be safe, as drugs are not formally allowed to be used during pregnancy. Drug exposure (somatostatin analogs) during early or whole pregnancy might increase the chance of a lower birth weight. Aggressive disease is uncommon and may urge individual decisions such as surgery or drug treatment during pregnancy or lactation.

Evaluation of the GHRH–arginine retest for young adolescents with childhood-onset GH deficiency

ObjectiveRetesting of adolescents with childhood-onset GH deficiency (GHD) is recommended, but age-related reference data are scarce. We aimed to establish a cut-off value for the GHRH–arginine test (GHRH+ARG) at the typical age of retesting at near-adult height. DesignsWe retrospectively studied 149 patients (108 males) with childhood-onset GHD aged 16.8±1.7years (mean±SD) with a BMI of 20.9±3.5kg/m2 who had received GHRH+ARG in one single center during 8consecutiveyears. Based on the IGF-I serum concentration falling below −2 SDS when off GH, 22 patients suffered from severe GHD of adulthood while 122 were GH sufficient. Five patients could not be determined definitively. GH and IGF-I were measured by in-house RIAs. IGF-I values were transformed into age-related SDS values. ROC-analysis was used to determine the cut-off value. ResultsFor GHRH+ARG, a cut-off limit of 15.9ng/ml had the highest pair of sensitivity (91%) and specificity (88%). GH peaks of the patients with a normal BMI between −1 and 0 SDS were higher than those with a high BMI >1 SDS (p<0.01). ConclusionsWhen retesting adolescents at near-adult height for severe GHD of adulthood, a GH value of <15.9ng/ml in GHRH+ARG is discriminatory with good accuracy. Conversion factors for other GH assays in use are provided. A rational decision for or against the continuation of GH therapy into adulthood can be made based on the clinical history of the patient and the combination of the GHRH+ARG retest result and the IGF-I serum concentrations when off GH.

Some Performance Genes in Dairy Cattle in Relation to Milk Composition

Different dairy cattle breeds in Egypt that notes deviation in milk composition and daily milk production which related to diversity in genetic character. To study the diversity between three main breeds (Native, Holstein and brown Swiss) in Egypt based on genetic polymorphism and biochemical investigation. In order to study the polymorphism of performance genes as (GH and PRL), the PCR-RFLP method was performed. A 428bp and 156pb fragments of GH and PRL genes respectively were amplified via PCR. These fragments were then restricted with the enzymes Alu1and RsaI respectively. In this study present two alleles,V and L in GH and A, B in PRL. L allele for GH and A allele for PRL are predominant and higher polymorphic in Holstein breed than Brown Swiss and Baladi breed. Hormonal assay for GH and PRL were measured in high and low producers in three breeds of cattle under study which give highly average level in high and low producers Holstein breed when compared to Brown Swiss and Baladi breeds, and this indicated when measured daily milk yield in high and low producers Holstein breed highly yield when compared to other breeds. Inversely expected for milk constituent (protein, fat, lactose, ash and total solid) high level were measured in low and high producers Baladi breed when compared two other breeds. This concluded that there was significance difference in some performance genes (GH, PRL) in genetic polymorphism and biochemical deviation in three breeds, the best one for milk production is Holstein breed than other two breeds.

Overcoming the need for a second test: an evaluation of anthropometric, biochemical, and radiological parameters in the diagnosis of GH deficiency

• Poor reproducibility • Variability of different GH assays • Invasive • Time consuming • Expensive ~ £1,000 per test • Potential risks & side effects (dependent on test): hypoglycaemia, hypotension, anaphylaxis, vomiting, nausea, hypokalaemia • Validity: arbitrary cut off regardless of stimulus/ assay (USA <10 μg/l, UK <6.7 μg/l) • Dependent on age, body composition, pubertal status, nutritional status, GH secretion prior to testing • False negatives (“fail”) in prepubertal children: no consensus on sex steroid priming • Non-physiological. 1. To interrogate clinical, biochemical and radiological parameters in the diagnosis of IGHD and Idiopathic Short Stature (ISS) in an attempt to reduce the need for dynamic function testing, and therefore the need for confirmatory testing. 2. To determine what proportion of children diagnosed with IGHD continue to be GH deficient after attaining their final height

Reevaluation of Acromegalic Patients in Long-Term Remission according to Newly Proposed Consensus Criteria for Control of Disease.

Acromegaly guidelines updated in 2010 revisited criteria of disease control: if applied, it is likely that a percentage of patients previously considered as cured might present postglucose GH nadir levels not adequately suppressed, with potential implications on management. This study explored GH secretion, as well as hormonal, clinical, neuroradiological, metabolic, and comorbid profile in a cohort of 40 acromegalic patients considered cured on the basis of the previous guidelines after a mean follow-up period of 17.2 years from remission, in order to assess the impact of the current criteria. At the last follow-up visit, in the presence of normal IGF-I concentrations, postglucose GH nadir was over 0.4 μg/L in 11 patients (Group A) and below 0.4 μg/L in 29 patients (Group B); moreover, Group A showed higher basal GH levels than Group B, whereas a significant decline of both GH and postglucose GH nadir levels during the follow-up was observed in Group B only. No differences in other evaluated parameters were found. These results seem to suggest that acromegalic patients considered cured on the basis of previous guidelines do not need a more intensive monitoring than patients who met the current criteria of disease control, supporting instead that the cut-off of 0.4 mcg/L might be too low for the currently used GH assay.

MANAGEMENT OF ENDOCRINE DISEASE: GH excess: diagnosis and medical therapy

Acromegaly is predominantly caused by a pituitary adenoma, which secretes an excess of GH resulting in increased IGF1 levels. Most of the GH assays used currently measure only the levels of the 22 kDa form of GH. In theory, the diagnostic sensitivity may be lower compared with the previous assays, which have used polyclonal antibodies. Many GH-secreting adenomas are plurihormonal and may co-secrete prolactin, TSH and α-subunit. Hyperprolactinaemia is found in 30-40% of patients with acromegaly, and hyperprolactinaemia may occasionally be diagnosed before acromegaly is apparent. Although trans-sphenoidal surgery of a GH-secreting adenoma remains the first treatment at most centres, the role of somatostatin analogues, octreotide long-acting repeatable and lanreotide Autogel as primary therapy is still the subject of some debate. Although the normalisation of GH and IGF1 levels is the main objective in all patients with acromegaly, GH and IGF1 levels may be discordant, especially during somatostatin analogue therapy. This discordance usually takes the form of high GH levels and an IGF1 level towards the upper limit of the normal range. Pasireotide, a new somatostatin analogue, may be more efficacious in some patients, but the drug has not yet been registered for acromegaly. Papers published on pasireotide have reported an increased risk of diabetes mellitus due to a reduction in insulin levels. Pegvisomant, the GH receptor antagonist, is indicated - alone or in combination with a somatostatin analogue - in most patients who fail to enter remission on a somatostatin analogue. Dopamine-D2-agonists may be effective as monotherapy in a few patients, but it may prove necessary to apply combination therapy involving a somatostatin analogue and/or pegvisomant.

Comparison of two growth hormone stimulation tests and their cut-off limits in healthy adults at an outpatient clinic

ObjectiveA peak GH less than 3μg/L to insulin tolerance test (ITT) is commonly used as a threshold indicating severe adult GH deficiency (GHD). This cut-off is based on results obtained by polyclonal radioimmunoassays preferably under standard conditions at hospital. Our aim was to evaluate the validity of this cut-off limit using two currently used immunometric GH assays and to compare GH responses in the ITT and the GH releasing hormone+arginine (GHRH+ARG) test in healthy adults at our outpatient endocrine unit. DesignITT was performed on 73 subjects and the GHRH+ARG test on those 28 who showed insufficient response to the ITT. MethodsGH was measured by an immunofluorometric and immunochemiluminometric assay. ResultsGH peak above 3μg/L was observed in 56% of the healthy volunteers with adequate hypoglycemia in the ITT. Among the 28 subjects with a peak GH below 3μg/L, only two overweight men had a GH peak response below the commonly used cut-off limit of 9.1μg/L in the GHRH+ARG test. ConclusionsLean healthy adults could erroneously be classified as GH deficient by the ITT while their results in the GHRH+ARG test were normal. The GH results are highly dependent on the immunoassay used, but false positive results in the ITT are often obtained even if lower cutoff limits determined on the basis on the calibration of the GH assay are used. Confounding factors seemed to blunt the GH response to the ITT more than to the GHRH+ARG test at our outpatient clinic.

Novel Use of Endogenous GH-Measurement Directly after Transsphenoidal Microsurgery in Acromegaly Treated with Pegvisomant

The GH receptor antagonist pegvisomant is increasingly used as therapy in acromegaly. Pituitary surgery might be indicated on pegvisomant treatment, due to side effects, adenoma growth or intention to cure after primary treatment. This study was initiated to clarify if, and when, GH measurement could be useful postoperatively with an assay specific for endogenous GH that does not cross-react with pegvisomant. This study was designed as a prospective study in 2006 with the German Pituitary Working Group. Only 2 cases with potentially resectable adenomas from the German Pegvisomant Observational Study (GPOS) had been operated. Now with a post-operative follow-up of more than 5 years in these 2 cases, the usefulness of immediate pre-operative GH measurement shortly after pegvisomant treatment was evaluated. In both patients a steep decline of endogenous GH after transnasal microsurgery could be proven by using the special GH assay after near radical or radical removal, of the GH secreting adenomas respectively. Conventional GH assays showed no effect. GH half-life was more than 20 min in the patient with a small invasive residual adenoma and less than 20 min in the cured patient. Endogenous GH-levels declined to less than 1 ng/ml in the days after surgery in the patient with long-term cure. Measurement of endogenous GH in this special subgroup of patients under pegvisomant therapy can be used to decide upon early reoperation. Thus the beneficial effect of pegvisomant on acromegalic symptoms can be kept without interfering with post-operative monitoring of GH levels.

Idiopathic Adult Growth Hormone Deficiency

GH secretion is controlled by hypothalamic as well as intrapituitary and peripheral signals, all of which converge upon the somatotroph, resulting in integrated GH synthesis and secretion. Enabling an accurate diagnosis of idiopathic adult GH deficiency (IAGHD) is challenged by the pulsatility of GH secretion, provocative test result variability, and suboptimal GH assay standardization. The spectrum between attenuated GH secretion associated with the normal aging process and with obesity and truly well-defined IAGHD is not distinct and may mislead the diagnosis. Adult-onset GHD is mainly caused by an acquired pituitary deficiency, commonly including prior head/neck irradiation, or an expanding pituitary mass causing functional somatotroph compression. To what extent rare cryptic causes account for those patients seemingly classified as IAGHD is unclear. About 15% of patients with adult GHD and receiving GH replacement in open-label surveillance studies are reported as being due to an idiopathic cause. These patients may also reflect a pool of subjects with an as yet to be determined occult defect, or those with unclear or incomplete medical histories (including forgotten past sports head injury or motor vehicle accident). Therefore, submaximal diagnostic evaluation likely leads to an inadvertent diagnosis of IAGHD. In these latter cases, adherence to rigorous biochemical diagnostic criteria and etiology exclusion may result in reclassification of a subset of these patients to a distinct known acquired etiology, or as GH-replete. Accordingly, rigorously verified IAGHD likely comprises less than 10% of adult GHD patients, an already rare disorder. Regardless of etiology, patients with adult GHD, including those with IAGHD, exhibit a well-defined clinical phenotype including increased fat mass, loss of lean muscle mass, decreased bone mass, and enhanced cardiac morbidity. Definition of unique efficacy and dosing parameters for GH replacement and resultant therapeutic efficacy markers in true IAGHD requires prospective study.

Detecting and solving the interference of pregnancy serum, in a GH immunometric assay

BackgroundHigh homology of GH with placental GH (pGH) and hPL frequently resulted in falsely high GH levels in competitive immunoassays during pregnancy. However, in immunometric assays, falsely high or low GH levels can result from GH-like molecules binding to both or only one monoclonal antibody. Since our GH-IFMA assay detected GH suppression in both normal and acromegalic pregnancies, we evaluated potential negative interference of pregnancy serum in the assay. MethodsGH was measured in samples from acromegalic patients with and without the addition of normal pregnancy serum using a sensitive in-house two-step GH-IFMA (no crossreactivity with pGH, Prolactin or hPL). Standard GH assay curves were run with and without pGH (20 and 22K). Pegvisomant, a GH-antagonist with high homology to GH, was also tested for cross-reactivity. ResultsAddition of pregnancy serum to acromegaly serum resulted in marked decrease in GH, but addition of pGH did not change GH measurements. Redesign of the routine assay by switching the positions of the antibodies (“inverted” assay) completely abrogated the interference of pregnancy serum. GH by both routine and inverted assays declined progressively throughout pregnancy in controls, with higher nadir levels in the “inverted” assay (median 0.03μg/L vs 0.50μg/L, P<0.05). GH suppression during acromegalic pregnancy previously found with the routine assay was not observed in the “inverted” assay. Pegvisomant does not cross-react with GH in the “inverted” assay. ConclusionsGH measurements in pregnancy by immunometric assays must be made after exclusion of pregnancy serum interference by dilutional tests. Redesigning a two-step immunometric GH assay by switching the positions of the antibodies can be a successful strategy to abrogate such interference.

Growth hormone variants: a potential avenue for a better diagnostic characterization of growth hormone deficiency in children.

Human GH (hGH) is a heterogeneous protein hormone consisting of several isoforms. This heterogeneity is the consequence of multiple hGH genes, mRNA splicing, post-translational modifications, and peripheral metabolism, and it represents one important reason for the disparity among GH assay results from different laboratories. However, other factors are involved: a) interference from endogenous GH binding proteins; b) different specificities of anti- GH (monoclonal and polyclonal) antibodies; c) different matrix effects among the calibrators; d) the use of different calibrators. The measurement of GH levels in response to provocative testing is an essential part of the diagnosis of GH deficiency. For this purpose, an accurate, reproducible and universally valid GH measurement would be highly desirable, but, despite a huge number of efforts in clinical biochemistry, this goal remains elusive.

Labordiagnostik bei Wachstumshormon-assoziierten Erkrankungen/Biochemical diagnosis of growth hormone related diseases

Zusammenfassung Die Krankheitsbilder des Wachstumshormonmangels und des Wachstumshormonexzesses imponieren klinisch unterschiedlich vor und nach dem Abschluss des Längenwachstums. Stets jedoch bilden die Messung der zirkulierenden Konzentrationen von Wachstumshormon und Insulinartigem Wachstumsfaktor I (Insulin-like growth-factor I, IGF-I) die Basis der laborchemischen Diagnostik. Mit den Immunoassays stehen praktikable, sensitive und meist auch spezifische Methoden zur Messung beider Hormone zur Verfügung. Trotzdem bestehen nach wie vor gravierende Diskrepanzen zwischen den Messergebnissen verschiedener Assays. Diese Diskrepanzen sind vor allem bedingt durch Unterschiede in der Isoformspezifität der Assays, die Verwendung unterschiedlicher Standardpräparationen sowie die Interferenz von Bindungsproteinen. Die methodenbedingten Unterschiede in den Messergebnissen erschweren die allgemeine Anwendung publizierter diagnostischer Entscheidungsgrenzen. Auf einer interdisziplinären Konsensuskonferenz unter Beteiligung der Growth Hormone Research Society, der IGF Society, und der International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) wurden die bestehenden Probleme analysiert und mögliche Strategien zu einer Verbesserung der Vergleichbarkeit der Messergebnisse verschiedener GH- und IGF-I-Assays aufgezeigt. Derzeit bleibt jedoch in der klinischen Praxis die Anwendung methodenspezifischer, an gut charakterisierten Kollektiven gewonnener Referenzbereiche unabdingbar.

Biochemical diagnosis of growth hormone related diseases1)

Abstract The symptoms of growth hormone deficiency and growth hormone excess clinically impose differently before and after the completion of longitudinal growth. Always, however, biochemical diagnostics is based on the measurement of circulating concentrations of growth hormone and insulin-like growth factor I (IGF-I). Immunoassays are practical, sensitive, and mostly specific methods for measuring either hormone. There are, however, still serious discrepancies between the results reported from different assays. These discrepancies are mainly due to differences in the isoform specificity of assays, the use of different standard preparations, as well as the interference of binding proteins. The method-related differences in measured results make the general application of published diagnostic decision limits more difficult. At an interdisciplinary consensus conference, with the participation of the Growth Hormone Research Society, the IGF Society, and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), the existing problems were analyzed and possible strategies were highlighted to improve the comparability between results obtained from different GH and IGF-I assays. Currently, however, the use of method-specific reference ranges obtained from well-characterized cohorts continues to be essential in clinical practice.

Gender, Age, Body Mass Index, and IGF-I Individually and Jointly Determine Distinct GH Dynamics: Analyses in One Hundred Healthy Adults

GH secretion is quantifiable as mean, peak, and nadir GH concentrations; degree of irregularity (approximate entropy); and spikiness (brief staccato-like fluctuations). Distinct GH dynamics reflect relatively distinct (combinations of) subject variables, such as gender, age, body mass index (BMI), and IGF-I concentrations. The study took place at a clinical translational research unit. Subjects included 100 healthy adults ages 20-77 yr (59 women and 41 men), BMI 18-42 kg/m(2), and IGF-I 9.2-38 nmol/liter. Immunofluorometric GH assay was done on 10-min samples collected for 24 h. Stepwise forward-selection multivariate regression analysis revealed that mean GH concentrations were simultaneously determined (overall r = 0.36; P < 0.001) by gender (higher in women, P < 0.001), BMI (negatively, P < 0.001), and IGF-I (positively, P < 0.001). Peak GH levels were influenced (r = 0.28) by both BMI (P < 0.001) and IGF-I (P = 0.001). Nadir GH values were jointly affected by gender (higher in women, P = 0.005) and BMI (negatively, P = 0.001). GH approximate entropy was triply defined (r = 0.29) by gender (greater irregularity in women, P < 0.001), age (P = 0.022), and BMI (P = 0.008) and dually (r = 0.25) by gender (P = 0.0001) and BMI (P = 0.017) if sex steroids were included. GH spikiness was determined (r = 0.29) by gender (higher in women, P = 0.0016) and BMI (positively, P = 0.0002). In healthy adults, combinations of gender, age, BMI, and IGF-I specify distinct GH dynamics, thus requiring balanced representation of these variables in comparative GH studies.

Octreotide administration, under particular temporal conditions, enhances the responses of growth hormone to growth hormone-releasing hormone in normal subjects

Somatostatin not only inhibits basal and GHRH-stimulated GH secretion but might also enhance pituitary GH responsivity to GHRH under different temporal conditions. We investigated whether octreotide, a long-acting somatostatin analogue, has any positive actions on GHRH-induced GH release in normal human subjects. The study consisted of three protocols. At 0800 hours, after fasting overnight, all subjects received 1 microgram/kg GHRH i.v. bolus at 0 minutes. In each protocol, either octreotide (200 micrograms s.c.) or placebo were given respectively 8, 12, or 16 hours prior to GHRH challenge. Three groups of eight normal volunteers (four female and four male in each group), aged 18-35 years, were randomly assigned to each protocol. Growth hormone was measured by IRMA. Samples for GH assay were taken at -30 and 0 minutes and then at 15-minute intervals up to 120 minutes. When placebo or octreotide were administered 8 hours before GHRH, peak GH levels were respectively (mean +/- SE, mU/l) 56.2 +/- 16.6 and 60.8 +/- 11.4 (NS). Also, when placebo or the somatostatin analogue were administered 16 hours prior to GHRH, peak GH levels were comparable (61.0 +/- 7.4 vs 58.8 +/- 7.4, NS). However, in the group receiving placebo or octreotide 12 hours prior to GHRH, the GH responses to GHRH were clearly enhanced by octreotide administration (peak GH levels, mU/l, 55.6 +/- 21.6 vs 104.0 +/- 17.4, P < 0.02). This enhancement of GH responses was observed in all subjects. Octreotide administration did not affect GH responses to GHRH when given either 8 or 16 hours prior to GHRH. However, octreotide enhanced GHRH-induced GH release when administered 12 hours prior to GHRH. It thus appears that, under particular temporal conditions, octreotide may act positively on GH secretion in man.

Effect of physical fitness and endurance exercise on indirect biomarkers of growth hormone and insulin misuse: Immunoassay-based measurement in urine samples

Indirect biomarkers of recombinant human growth hormone (rhGH), insulin-like growth factor-I (IGF-I), insulin-like growth factor-II (IGF-II), insulin-like growth factor binding proteins (IGFBP-2 and IGFBP-3) and insulin (C-peptide) were measured together with urinary parameters of renal damage (β 2-microglobulin and proteinuria) by immunoassays, in house validated for the purpose, in 61 subjects (36 elite athletes, 18 recreational athletes and 7 sedentary individuals) with different levels of physical fitness and endurance exercise. Validation parameters were good for the evaluated assays, excluding a high inter-assay imprecision and inaccuracy of 24 and 26% obtained for GH assay. The range of concentrations found in urine samples under investigation was generally covered by the calibration curves of the studied immunoassays. However, for the samples below or above the calibration curve, opportune dilution or concentration were performed. Particularly, C-peptide samples had to be diluted 1:5 and β 2-microglobulin ones assayed using a triple sample volume, to fall within the calibration range. Urinary C-peptide was the only biomarker statistically higher in samples of elite athletes when compared to recreational athletes and sedentary individuals. Among elite athletes, taekwondo athletes showed the highest IGF-II basal values while weightlifting athletes showed the lower IGF-I and IGFBP-3 basal values. The trend observed in weightlifters basal samples was confirmed in their training samples: IGF-I, IGF-II, IGFBP-3 and β 2-microglobulin were lower in with respect to those from synchronised swimming. Over the training season, within athlete variability was observed for IGFBP-3 for weightlifting athletes. In the studied subjects, no direct associations were found between biomarkers of GH or insulin misuse and urinary parameters of renal damage, eventually due to high-workload endurance training. The variations observed in different biomarkers should be taken in consideration in the hypothesis of setting reference concentration ranges for doping detection.