Growth Hormone Assays Research Articles

In vivo and in vitro evidence for growth hormone-like bioactivity of Rhizoma Anemarrhenae extract

Certain herbs used in traditional Chinese medicine may produce a growth-enhancing effect by promoting the secretion of growth hormone (GH) by the pituitary gland or mimicking the function of GH. In this study, we aimed to identify herbs that could serve as GH alternatives. A reporter gene assay for GH was developed, and 100 different herbal extracts were assayed. We found that Rhizoma Anemarrhenae (RA) water extracts exhibited transactivation activities that stimulate the activation of signal transducer and activator of transcription 5 (STAT5). The growth-promoting effect of RA in NB2–11 cells was inhibited by co-treatment with GH receptor (GHR)-Fc fusion protein. Unlike GH, RA extracts did not enhance the growth of B16F10 melanoma cells. The activation of the Janus kinase 2-STAT5 signaling pathway was confirmed in both NB2–11 cells and WI-38 human normal lung fibroblasts; the activation was inhibited by co-treatment with GHR-Fc fusion protein. Docking analysis of the active ingredients of RA, including mangiferin, neomangiferin, isomangiferin, anemarsaponin E, 7-O-methylmangiferin, officinalisinin I, timosaponin BII, timosaponin AI, and timosaponin AIII, using SWISSDOCK indicated a direct interaction of these compounds with GHR. The growth-promoting effects and activation of STAT5 were also confirmed. Moreover, we found that RA extract significantly increased the height of the tibial growth plate and stimulated the production of insulin-like growth factor 1 in the serum, liver, and muscle tissues. Our findings provide evidence that herbal extracts, particularly, RA extracts, can promote growth by mimicking GH bioactivity.

Growth Hormone Stimulation Testing: To Test or Not to Test? That Is One of the Questions.

The evaluation of children with short stature includes monitoring over a prolonged period to establish a growth pattern as well as the exclusion of chronic medical conditions that affect growth. After a period of monitoring, evaluation, and screening, growth hormone stimulation testing is considered when the diagnosis of growth hormone deficiency (GHD) is entertained. Though flawed, growth hormone stimulation tests remain part of the comprehensive evaluation of growth and are essential for the diagnosis of growth hormone (GH) deficiency. Variables including testing length, growth hormone assay and diagnostic cut off affect results. Beyond the intrinsic issues of testing, results of GH stimulation testing can be influenced by patient characteristics. Various factors including age, gender, puberty, nutritional status and body weight modulate the secretion of GH.

Current concepts of the diagnosis of adult growth hormone deficiency

In adults, growth hormone (GH) deficiency is associated with increased visceral adiposity, decreased lean body mass, bone mineral density and exercise capacity, dyslipidemia, insulin resistance, increased cardiometabolic and fracture risk, and impaired quality of life. The aim of the present article is to review the diagnosis of GH deficiency in adults. To avoid overdiagnosis of GH deficiency, it is critical to evaluate only patients at risk for pituitary dysfunction, including those who have had sellar masses, pituitary surgery, radiation therapy, traumatic brain injury, subarachnoid hemorrhage or childhood onset GH deficiency. Evaluation for GH deficiency should be undertaken after testing and replacement of other pituitary hormone deficits. Since GH secretion is pulsatile, measuring serum GH levels randomly is not helpful in establishing the diagnosis of GH deficiency. Serum insulin-like growth factor I (IGF-I) levels lack substantial diurnal variation but also lack sufficient sensitivity and specificity in the diagnosis of GH deficiency in adults. However, adults with multiple (≥3) additional pituitary hormone deficiencies, risk factors for hypopituitarism and low serum IGF-I levels are very likely to be GH deficient. In most cases, the diagnosis of GH deficiency requires stimulation testing. These tests involve the administration of a pharmacologic agent that normally stimulates GH release from pituitary somatotrophs, including insulin, glucagon, growth hormone releasing hormone-arginine or macimorelin, followed by sampling of serum specimens at regular intervals for GH assay. Patients with a peak GH level that is below a predetermined cutpoint are classified as GH deficient. A systematic approach to the diagnosis of GH deficiency is essential in order to accurately identify adults who may benefit from GH replacement.

MON-298 IGF-1 in the Early Post-operative Assessment of Acromegaly

Introduction: Transsphenoidal surgery is recommended as first line therapy in the vast majority of patients with acromegaly. Successful surgical intervention is determined by normalization of insulin like-growth factor (IGF) - 1 and adequate suppression of growth hormone (GH) during glucose GH suppression test or random GH levels <1.0 ng/mL. Given the long half-life of IGF-1, evolution of IGF-1 and GH assays and limitations of GH suppression test, clinicians remain reliant on IGF-1 results 3–6 months following surgery to assess disease remission following surgical intervention. This can lead to delayed treatment of patients with persistent disease and significantly increase patient anxiety. Aim: To determine if IGF-1 levels at 6 weeks were equally predictive of surgical outcomes when compared to IGF-1 levels at 3–6 months postoperative. Methods: Retrospective review of patients with newly diagnosed acromegaly who had surgery between 2010–2019 and had post-operative IGF-1 level measured at 6 weeks and 3–6 months. IGF-1 was measured using the Siemens Immulite assay until 2016 when it was replaced by a LC-MS/MS assay. IGF-1 measurements at 6 weeks are obtained based on clinician discretion. Results: 69 patients (mean age 49 ± 14.8, female 31/69, 44.9%) with acromegaly had surgery and IGF-1 follow-up measurements at 6 weeks and 3–6 months. Persistent acromegaly was noted in 45/69 at 3–6 months. The median IGF-1 pre-operative was 701 ng/ mL (289–1600), 6 weeks postoperative was 286 ng/ mL (109–1038) and at 3–6 months was 267 ng/ mL (77–996). The median pre-operative IGF-1 was significantly higher than the median IGF-1 level at 6 weeks and 3–6 months (P=<0.001). Although a statistically significant difference was seen between IGF-1 levels at 6 weeks and 3–6 months, the mean difference between these time points was small (20 ng/mL, P=<0.001). There was a greater percent reduction in IGF-1 at 6 weeks following surgery in those who had a normal IGF-1 at 3–6 months compared to those who did not (63% vs 35%, P=<0.01). Among patients who were deemed in remission at 3–6 months (24/69, 35%), 3/24 patients (all male with macroadenoma and no cavernous sinus invasion) had mildly elevated IGF-1 levels at 6 weeks (≤1.12 upper limit of normal) which subsequently normalized. In all of these patients, GH was <1 ng/mL post-op. In 1 male (macroadenoma and cavernous sinus invasion), IGF-1 levels increased from normal at 6 weeks to abnormal when measured at 3–6 months. Conclusion: In the vast majority of patients, 6 weeks post-operative IGF-1 can be used to assess response to surgery avoiding a delay in treatment. However, we would recommend repeating IGF-1 levels at 3–6 months in those who have marginally elevated IGF-1 above normal (≤ 1.12), without cavernous sinus invasion and a post-operative GH of <1 ng/mL prior to intervening if the IGF-1 is elevated 6 weeks as the IGF-1 may normalize.

Laboratory investigations in the diagnosis and follow-up of GH-related disorders.

In addition to auxiological, clinical and metabolic features measurements of growth hormone (GH) and insulin-like growth factor I (IGF-I) complement our tools in diagnosis and follow-up of GH-related disorders. While comparably robust during the pre-analytical phase, measurement and interpretation of concentrations of both hormones can be challenging due to analytical issues and biological confounders. Assay methods differ in terms of antibody specificity, interference from binding proteins, reference preparations and sensitivity. GH assays have different specificity towards different GH-isoforms (e.g. 20 kDa GH, placental GH) and interference from the GH antagonist Pegvisomant. The efficacy to prevent binding protein interference is most important in IGF-I assays. Methodological differences between assays require that reference intervals and diagnostic cut-offs are assay-specific. Among biological variables, pubertal development and age are most relevant for IGF-I, making detailed reference intervals mandatory for interpretation. GH has pulsatile secretion and short half-life. Its concentration is modified by acute factors such as stress, exercise and sleep, but also by intake of oral estrogens and anthropometric factors (e.g. BMI). Other GH dependent biomarkers such as free IGF-I, IGF binding protein 3 (IGFBP 3) and acid labile subunit (ALS) have been proposed. Their concentrations largely mirror the information obtained through measurement of IGF-I, but their measurement can be helpful in particular situations. In this review, we describe the evolution of analytical methods to measure biomarkers of GH action, the impact of the methodological changes on laboratory results and the need to include biological variables in their interpretation. Arch Endocrinol Metab. 2019;63(6):618-29.

American Association of Clinical Endocrinologists and American College of Endocrinology Guidelines for Management of Growth Hormone Deficiency in Adults and Patients Transitioning from Pediatric to Adult Care

American Association of Clinical Endocrinologists and American College of Endocrinology Guidelines for Management of Growth Hormone Deficiency in Adults and Patients Transitioning from Pediatric to Adult Care

A case of 'micromegaly': need for revision of oral glucose tolerance test (OGTT) cut-offs with modern growth hormone assays in acromegaly

A case of 'micromegaly': need for revision of oral glucose tolerance test (OGTT) cut-offs with modern growth hormone assays in acromegaly

Growth hormone of dried blood spot for the diagnosis of growth hormone deficiency

The diagnosis of growth hormone deficiency (GHD) is difficult to determine, and could be associated with severe complications, especially in the neonatal period. The stimulation test of growth hormone (GH) secretion is considered the gold standard for diagnosis, but it has methodological complications and is associated with adverse effects. Neonates present physiological increased secretion of GH, representing a diagnostic window. To evaluate if the dried blood spot on filter paper obtained in the neonatal period, as part of a neonatal screening for con genital hypothyroidism and phenylketonuria, allows differentiating patients with GHD from those who do not have it. Study of cases and controls by measuring the GH concen tration in dried blood spot on filter paper obtained in the neonatal period, comparing controls with GHD with cases with discarded deficiency. The sample was extracted from the filter paper, obtaining two 0.125 inch discs per each patient from the center of the blood spot on the paper, for a highly sen sitive ELISA assay for human GH based on the use of polyclonal antibodies against 22 kDa recom binant human GH. Seven cases of GHD and ten controls were obtained. The median GH concentration of the dried blood spot in the cases is 2.0 ng/ml (Interquartile range 3.6 ng/ml) and 2.05 ng/ml (Interquartile range 2.0 ng/ml) in the controls, Mann-Whitney U test 30.5 (p = 0.68). The two cases with multiple pituitary-hormone deficiency (MPHD) present concentrations lower than 1 ng/ml. The dried blood spot sample did not differentiate GHD patients from control cases, although MPHD cases present much lower concentrations compared to isolated growth hor mone deficiency (IGHD).

Is GH nadir during OGTT a reliable test for diagnosis of acromegaly in patients with abnormal glucose metabolism?

The growth hormone (GH) nadir during oral glucose tolerance test (OGTT) is the gold standard diagnostic test for acromegaly. The utility of OGTT-GH suppression test in patients with abnormal glucose metabolism (AGM) has not been well established. In this study, we compared the GH nadir during OGTT in patients evaluated for acromegaly in the presence and absence of AGM. This is a retrospective cohort study of patients with acromegaly (G1, n = 40) and a group in whom acromegaly was not confirmed (G2, n = 53) who had OGTT-GH suppression test during 2000-2012, using a monoclonal GH immunoenzymatic assay. The patients were categorized as having normal glucose metabolism (NGM) or AGM. GH nadir during OGTT in each group were compared. In G1 and G2, 17 and 19 patients had AGM, respectively. Among 17 patients with diabetes, median HbA1C was 7% (range 5.7-9.6%). All except one patient had HbA1C< 8%. There was no difference in the GH nadir in patients with or without AGM within G1 (p = 0.15) and G2 (p = 0.43). All G1 patients with AGM had GH nadir > 0.4 µg/L. Four G1 patients with NGM had GH nadir<0.4 µg/L. All G2 patients had GH nadir < 0.4 µg/L, except one with NGM and GH nadir of 0.4 µg/L. Using highly sensitive GH assay, a GH nadir ≥ 0.4 µg/L during the OGTT-GH suppression test may be used for diagnosis of acromegaly in patients with AGM in the absence of poorly controlled diabetes.

The ongoing challenge of discrepant growth hormone and insulin-like growth factor I results in the evaluation of treated acromegalic patients: a systematic review and meta-analysis.

Growth hormone (GH) and insulin-like growth factor I (IGF-I) are the principal biomarkers used to assess disease activity in acromegaly, and any discrepancy between them renders interpretation of results inconclusive. Purpose of this study was to assess the frequency of this discrepancy and identify parameters that might affect its occurrence. A systematic review of MEDLINE and Scopus was performed (1987-2013) followed by a meta-analysis to address the frequency of discrepant results between GH and IGF-I levels. Meta-regression and subgroup analyses were performed assessing the effects of the year of publication, the different types of GH testing and GH assays used, as well as the impact of treatment with somatostatin analogues (SSAs) on the occurrence of this discrepancy. The analysis retrieved 39 eligible studies totalling 7071 patients. The pooled discordance rate between GH and IGF-I was 25·7% (95% CI: 22·3-29·4), and the predominant format was that of elevated IGF-I with normal GH levels (15·3%, 95% CI: 12·5-18·7). No significant correlation between the discordance rate and the year of publication was shown; whereas, the use of ultrasensitive GH assays resulted in higher discordance rates (30·7%, 95% CI: 25·9-35·9 vs 19·8%, 95% CI: 14·1-27·2, P = 0·04) as did treatment with SSAs (32·5%, 95% CI: 27·8-37·4) vs (21·6%, 95% CI: 17·8-25·6, P = 0·001). Discrepancy between GH and IGF-I results is encountered in a quarter of treated patients with acromegaly, especially when using ultrasensitive GH assays or in patients receiving SSAs, a fact that the clinician should take into consideration when making clinical decisions.

A half-century of studies of growth hormone insensitivity/Laron syndrome: A historical perspective

A growth hormone (GH) dependent substance responsible for sulfate uptake by costal cartilage of hypophysectomized rats, labeled sulfation factor, was reported in 1957. In 1962 the radioimmunoassay for GH was described. The clinical picture of severe GH deficiency but with high serum concentrations of GH was reported in 3 siblings in 1966 and followed by a 1968 report of 22 patients belonging to 14 consanguineous oriental Jewish families in Israel. Defective sulfation factor generation was demonstrated in 15 of these individuals and in a 1971 report; FFA response to IV GH and growth response to GH injections suggested competitive saturation of peripheral tissue receptors by an abnormal GH. However, studies published in 1973 demonstrated normal fractionation of their circulating GH, and normal binding of GH from 22 patients to various antisera used for radioimmunoassay. In 1976, the Israeli investigators reported that circulating GH from 7 patients reacted normally in the recently developed radioreceptor assay for GH. In 1984, using hepatic microsome pellets, they demonstrated that the defect was a failure of GH binding to receptors. Characterization of the human GH receptor (GHR) gene, reported in 1989, included the initial description of a genetic defect of the GHR in 2 of 9 Israeli patients. At about the same time began the identification in Ecuador of what was to become the largest population of GH insensitivity in the world, ~100 individuals, and the only substantial population with a common mutation of the GH receptor. Treatment studies with recombinant IGF-I began in 1990. Growth response was modest compared to that of GH treated GH deficient subjects. The spectrum of GH insensitivity has expanded beyond GH receptor deficiency to include postreceptor abnormalities: IGF-I gene mutation (1996); IGF-I receptor mutation (2003); signal transducer and activator of transcription 5b mutation (2003); and mutation of the GH-dependent acid labile subunit (2004). ConclusionRare conditions of GH insensitivity caused by GH receptor and postreceptor abnormalities have provided insights into the processes of growth, body composition, and metabolism.

Controversies in the diagnosis and management of growth hormone deficiency in childhood and adolescence.

Growth hormone deficiency (GHD) is a rare but important cause of short stature in childhood with a prevalence of 1 in 4000. The diagnosis is currently based on an assessment of auxology along with supporting evidence from biochemical and neuroradiological studies. There are significant controversies in the diagnosis and management of GHD. Growth hormone (GH) stimulation tests continue to play a key role in GHD diagnosis but the measured GH concentration can vary significantly with stimulation test and GH assay used, creating difficulties for diagnostic accuracy. Such issues along with the use of adjunct biochemical markers such as IGF-I and IGFBP-3 for the diagnosis of GHD, will be discussed in this review. Additionally, the treatment of GHD remains a source of much debate; there is no consensus on the best mechanism for determining the starting dose of GH in patients with GHD. Weight and prediction based models will be discussed along with different mechanisms for dose adjustment during treatment (auxology or IGF-I targeting approaches). At the end of growth and childhood treatment, many subjects diagnosed with isolated GHD re-test normal. It is not clear if this represents a form of transient GHD or a false positive diagnosis during childhood. Given the difficulties inherent in the diagnosis of GHD, an early reassessment of the diagnosis in those who respond poorly to GH is to be recommended.

PO-0091 5 Year Old Girl With Disproportionate Short Stature With Failure To Thrive And Dysmorphism: Rare Case Of Scheie Syndrome

Background Hurler-Scheie Syndrome is an autosomal recessive mucopolysaccharidois resulting in reduced activity of α-L-iduronidase with accumulation of heparin and dermatan sulphate. Scheie syndrome represents less severely affected form with varied clinical features. Case Report 5 year female, first born child of 2nd degree consanguineous Egyptian parents, referred for short stature presented with following features. On examination: Length: 88 cm; Upper: Lower segment=1:1.3; weight: 12.3 kg; Head circumference: 51 cm Protuberant abdomen, mild proptosis, enlarged skull, prominent forehead, low set ears, simian crease, clawed hand, mild kyphosis, strabismus, normal IQ, hepatomegaly. Investigation: USG: hepatomegaly, Karyotyping normal Mild delay bone age; Elevated TSH, low T4; tissue transglutaminase normal; sweat chloride test normal; ammonia, lactate normal; growth hormone assay normal; Deficient enzyme in fibroblast confirmed diagnosis of Scheie syndrome Discussion Scheie syndrome is an autosomal recessive, rare lysosomal storage disease, with skeletal deformities and motor delay; described first in 1972; caused by mutations in IDUA gene (4p16.3) leading to partial deficiency in alpha-L-iduronidase enzyme and lysosomal accumulation of dermatan and heparan sulfate. Genetic testing is available. Antenatal diagnosis done by measurement of enzymatic activity in chorionic villus/ amniocytes and by genetic testing (if disease-causing mutation is known). Genetic counselling is recommended. Management is multidisciplinary including physiotherapy (to maintain range of movement); bone marrow or umbilical cord blood transplant (to preserve neurocognition, improve somatic disease and increase survival). Enzyme replacement therapy slows disease progression. Conclusion Scheie syndrome should be considered in differential diagnosis of disproportionate short stature with dysmorphism, failure to thrive with normal IQ.

English

The aim of the study was to illustrate the radio-receptor assay of beetal recombinant caprine growth hormone (rcGH). Tracer ( 125 I-rcGH) was prepared by iodinating beetal rcGH with iodine-125 and its biological activity was analyzed by rabbit anti-rcGH antibodies. Liver microsomal membranes of the Bovidae species (caprine, ovine and bovine) were prepared to study the binding properties of beetal rcGH. The tracer binding was dependent on receptor protein concentration, tracer counts, temperature, time of incubation and assay pH. The maximum percentage specific binding of the tracer to the microsomal membrane was 45% in 32 h at 4°C. In cross-reactive study, human GH competed and displaced the 125 I-rcGH by binding effectively to the cGH receptor. Scatchard analysis of the rcGH binding suggested a single class of binding site to the caprine microsomal membrane with an affinity of 337.1 ± 82.94 × 10 9 M -1 and capacity of 57.61 ± 4.23 fmol mg -1 while rcGH binding affinity and capacity to the ovine and bovine receptor protein showed 365.4 ± 66.82 × 10 9 M -1 , 57.69 ± 3.23 (fmol mg -1 ) and 392.6 ± 56.25 × 10 9 M -1 , 56.8 ± 2.56 (fmol mg -1 ) respectively. This study provides data for beetal rcGH interaction with microsomal membrane that shall be beneficial to study hormone receptor interactions of other Bovidae species. Keywords: Beetal recombinant caprine growth hormone, Bovidae, iodine-125, microsomal membrane, receptor protein African Journal of Biotechnology , Vol 13(30) 3081-3091

Transsphenoidal surgery for acromegaly: predicting remission with early postoperative growth hormone assays.

Early detection of residual disease may benefit management strategies in patients undergoing transsphenoidal surgery for acromegaly. This requires establishing objective thresholds for early postoperative growth hormone (GH) assays, and incorporating these parameters into a scale for outcome prediction. We analyzed a database containing the records of 86 patients who had undergone gross total transsphenoidal resection of GH-secreting pituitary adenomas. Early postoperative biochemical testing included a morning fasting basal GH assay on the first postoperative day (POD1) and a second GH assay following suppression with 100 g of oral glucose on the seventh postoperative day (POD7). Remission was defined as a normal IGF-1 with either a GH nadir <0.4 ng/ml following suppression with oral glucose or a basal fasting GH <1 ng/ml on follow-up dated >3 months after surgery. Receiver operator characteristic (ROC) curves identified optimal thresholds for all biochemical parameters. Logistic regression analysis assessed the statistical significance of factors associated with cure. A point system was developed, employing regression coefficients obtained from the multivariate statistical model to quantify the impact of each predictor on cure. Remission was achieved in 34.6 % of patients and was associated with smaller, non-invasive tumors with lower preoperative, POD1 and POD7 GH levels. Optimal thresholds obtained from the ROC analysis suggested that lower POD1 and POD7 GH values provided good sensitivity and specificity for cure, despite modest predictive values. The model with the best ability to predict outcome included size, POD1 GH and POD7 GH levels, with a score of ≥95 demonstrating high specificity for prediction of remission. Early postoperative GH assays are highly sensitivity and specific. The scoring system that we propose provided excellent predictive value and requires further validation in larger cohorts and in different populations. The model may help guide the intensity of follow-up and enable early identification of residual disease.

Discordance between growth hormone and insulin-like growth factor-1 after pituitary surgery for acromegaly: a stepwise approach and management

Follow-up management of patients with acromegaly after pituitary surgery is performed by conducting biochemical assays of growth hormone (GH) and insulin-like growth factor-1 (IGF1). Despite concordant results of these two tests in the majority of cases, there is increasing recognition of patients who show persistent or intermittent discordance between GH and IGF1 (normal GH and elevated IGF1 or vice versa). In this narrative review, the last three decades materials on the issue of discrepancy between GH and IGF1 were thoroughly assessed. Various studies have obtained different discordance rates, ranging from 5.4 to 39.5%. At present, despite the use of current sensitive assays and more stringent criteria to define remission, the rate of discordance still remains high. A number of mechanisms have been proposed to explain the postoperative discordance of GH and IGF1 including; altered dynamics of the GH secretion after surgery, early postoperative hormone assay, inaccurate or less sensitive tests and laboratory errors, too high cut-off point for GH suppression in the GH assays, GH nadir values not adjusted to age, sex, and body mass index, the influence of concomitant medication, co-existing physiologic and pathologic conditions, and many other proposed reasons. Nevertheless, the underlying mechanisms are still far from clear, and the solution continues to evade complete elucidation. Similarly, the impacts of such a discrepancy over mortality and morbidity and the risk of biochemical and/or clinical recurrence are unclear. As a challenging clinical problem, a stepwise evaluation and management of these patients appears to be more rational.

Determination of Nadir Growth Hormone Concentartion Cutoff In Patients with Acromegaly

ObjectiveThe purpose of this study was to define an appropriate nadir growth hormone (nGH) cutoff for patients with acromegaly in remission using the Access Ultrasensitive human growth hormone (hGH) assay (Beckman Coulter, Brea, CA). MethodsThis cross-sectional study included 55 acromegalic subjects and 41 healthy adult volunteers. All subjects underwent oral glucose tolerance testing (OGTT) for growth hormones (GHs). An optimal cutoff for nGH for patients with active disease versus those in remission was determined using receiver-operating curve analysis. ResultsThe nGH of 0.53 ng/mL revealed a sensitivity of 97% (95% confidence interval [CI], 83-100%) and a specificity of 100% (95% CI, 82-100%). All 22 patients with acromegaly in remission suppressed GH to <1 ng/mL, 20/22 (91%) suppressed to <0.4 ng/mL, and 19/22 (86%) of subjects suppressed to <0.3 ng/mL (the maximum nGH measured in our healthy volunteer group). ConclusionWhen using the Access Ultrasensitive hGH assay for OGTT, a cutoff of 0.53 ng/mL was found to most accurately differentiate patients with acromegaly in remission from those with active disease. (Endocr Pract. 2013;19:937-945)

Establishment and characterization of dairy cow growth hormone secreting anterior pituitary cell model

A dairy cow anterior pituitary cell (DCAPC) model was established in vitro for the study of growth hormone (GH) synthesis and secretion in the anterior pituitary gland of the dairy cow. Pituitary glands were obtained from Holstein dairy cows' heads cut by electric saw, and the posterior pituitary glands were removed to obtain integrated anterior pituitary glands. Immunohistochemistry assay of GH in the anterior pituitary glands showed that most somatotrophs were located within the lateral wings of the anterior pituitary. Tissues of the lateral wings of the anterior pituitary were dispersed and cultured in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum. The DCAPCs displayed a monolayer, cobblestone, epithelial-like morphology which are the typical characteristics of the anterior pituitary cells. The DCAPCs were subcultured continuously over ten passages. GH immunoreactivity was present in DCAPCs at passage 10. The transcription of the bovine GH mRNA in DCAPCs at passage 10 was decreased to below 50% compared with the lateral wings of the anterior pituitary tissues. Thus, our DCAPCs model is effective for the in vitro examination of GH synthesis and secretion in the dairy cow anterior pituitary gland. The effects of transforming growth factor beta 1 (TGF-β1) and interferon-γ (IFN-γ) on the expression of GH mRNA in DCAPCs at passage 3 were also investigated. There were no obvious changes in transcription of the GH gene after treatment with TGF-β1 for 24 h, while IFN-γ increased transcription of the GH gene in a dose-dependent manner.

Diagnosis of acromegaly: state of the art

Biochemical diagnosis of acromegaly relies on measurement of insulin-like growth factor-1 (IGF-1) and growth hormone (GH). An elevated IGF-1 level above the age- and gender-specific normal range and nonsuppression of GH to oral glucose load to a nadir < 0.4 ng/ml in sensitive assays are currently considered diagnostic of acromegaly. Lack of normative data for both IGF-1 and GH across a wide range of populations and ethnicities, interassay and intraassay laboratory variability, pulsatility of GH secretion, and effects of medications and hormones may confound interpretation of these biochemical tests. Clinical situations in which acromegaly should be suspected and/or investigated. Strengths and limitations of current IGF-1/GH assays are discussed. Clinical scenarios with discordant GH suppression test and IGF-1 levels and, briefly, acromegaly in pregnancy, prolactin-cosecreting tumors, familial acromegaly, and nonpituitary acromegaly are also discussed. Serum IGF-1 is the cornerstone and in most cases the stand-alone test in the diagnosis and follow-up in patients with acromegaly. Diagnosis depends on the accurate and reliable measurement of serum IGF-1. GH suppression testing is currently used in limited clinical setting. Standardization of IGF-1 assay and development of normative data across a wide population base are needed. Newer bioassays for IGF-1 hold promise for future.

Automated 22-kD Growth Hormone–Specific Assay without Interference from Pegvisomant

Large variability exists among different growth hormone (GH) assays owing to differences in calibration, antibody specificity, isoform recognition, and interference from GH binding protein (GHBP). The GH receptor antagonist Pegvisomant presents a new challenge because Pegvisomant interferes with many GH assays. A recent consensus conference established criteria for standardization and evaluation of GH assays. Following consensus recommendations, we developed a new GH assay on an automated analyzer (IDS-iSYS, Immunodiagnostic Systems). A monoclonal antibody not cross-reacting with Pegvisomant was combined with a monoclonal antibody specific for 22-kD GH. Isoform specificity and interference from GHBP was tested and compared to that seen in 2 existing automated GH assays (Siemens Immulite, Diasorin Liaison). We also compared GH concentrations measured by the 3 assays for healthy volunteers and patients with acromegaly receiving different treatments. Using the iSYS assay, we also established nadir GH values during oral glucose load and analyzed changes in endogenous GH during Pegvisomant treatment. Analytical and functional sensitivities were 0.01 μg/L and 0.04 μg/L, with a dynamic range from 0.04 to 100 μg/L. Intraassay CVs were 2%-4%, whereas interassay CVs were 5%-7% at GH concentrations between 1.7 and 27.5 μg/L. The assay was specific for 22-kD GH and not affected by GHBP. The presence of Pegvisomant, which leads to a negative bias on the Immulite and dramatic overestimation of GH on the Liaison, had no impact on the iSYS GH assay. The new assay fulfils recent consensus recommendations and presents a useful new tool for reliable measurement of GH.