Determinants of the growth hormone nadir during oral glucose tolerance test in adults

• Published in: European journal of endocrinology Vol. 181; no. 1; pp. 55 - 67
• Main Authors: Schilbach, Katharina, Gar, Christina, Lechner, Andreas, Nicolay, Shiva Sophia, Schwerdt, Laura, Haenelt, Michael, Dal, Jakob, Jørgensen, Jens-Otto Lunde, Störmann, Sylvère, Schopohl, Jochen, Bidlingmaier, Martin
• Format: Journal Article
• Language: English
• Published: England Bioscientifica Ltd 01.07.2019; Oxford University Press
• Subjects: 17β-Estradiol; Acromegaly; Acromegaly - diagnosis; Adult; Aged; Body weight; Clinical Study; Female; Females; Glucose; Glucose metabolism; Glucose tolerance; Glucose Tolerance Test; Growth hormones; Human Growth Hormone - analysis; Humans; Immunoassay - methods; Male; Menstrual cycle; Menstrual Cycle - blood; Middle Aged; Overweight; Post-menopause; Prospective Studies; Reference Values; Retrospective Studies; Sensitivity and Specificity; Young Adult
• ISSN: 0804-4643; 1479-683X; 1479-683X
• DOI: 10.1530/EJE-19-0139

Objective Growth hormone (GH) nadir (GHnadir) during oral glucose tolerance test (OGTT) is an important tool in diagnosing acromegaly, but data evaluating the need to adjust cut-offs to biological variables utilizing today's assay methods are scarce. We therefore investigated large cohorts of healthy subjects of both sexes to define normal GHnadir concentrations for a modern, sensitive, 22 kD-GH-specific assay. Design Multicenter study with prospective and retrospective cohorts (525 healthy adults: 405 females and 120 males). Methods GH concentrations were measured by the IDS-iSYS immunoassay after oral application of 75 g glucose. Results GHnadir concentrations (µg/L) were significantly higher in lean and normal weight subjects (group A) compared to overweight and obese subjects (group B); (males (M): A vs B, mean: 0.124 vs 0.065, P = 0.0317; premenopausal females without estradiol-containing OC (OC-EE) (FPRE): A vs B, mean: 0.179 vs 0.092, P < 0.0001; postmenopausal women (FPOST): A vs B, mean: 0.173 vs 0.078, P < 0.0061). Age, glucose metabolism and menstrual cycle had no impact on GHnadir. However, premenopausal females on OC-EE (FPREOC) exhibited significantly higher GHnadir compared to all other groups (all P < 0.0001). BMI had no impact on GHnadir in FPREOC (A vs B, mean: 0.624 vs 0.274, P = 0.1228). Conclusions BMI, sex and OC-EE intake are the major determinants for the GHnadir during OGTT in healthy adults. Using a modern sensitive GH assay, GHnadir concentrations in healthy subjects are distinctly lower than cut-offs used in previous guidelines for diagnosis and monitoring of acromegaly.