Optimal timing of blood samplings to detect GH inhibition during oral glucose tolerance test

• Published in: Journal of endocrinological investigation Vol. 45; no. 5; pp. 981 - 987
• Main Authors: Bioletto, F., Prencipe, N., Berton, A. M., Bona, C., Varaldo, E., Gasco, V., Ghigo, E., Grottoli, S.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.05.2022; Springer Nature B.V
• Subjects: Accuracy; Acromegaly; Acromegaly - diagnosis; Blood Specimen Collection; Cohort Studies; Endocrinology; Glucose tolerance; Glucose Tolerance Test; Human Growth Hormone; Humans; Insulin-Like Growth Factor I; Internal Medicine; Medicine; Medicine & Public Health; Metabolic Diseases; Original Article; Acromegaly; Oral glucose tolerance test; Growth hormone suppression; Growth hormone; Acromegaly diagnosis
• ISSN: 1720-8386; 0391-4097; 1720-8386
• DOI: 10.1007/s40618-021-01731-0

Background In patients with suspected acromegaly, evaluation of IGF-I is recommended as first-line test, while the assessment of GH-nadir during oral glucose tolerance test (OGTT) is advised as confirmatory test. The procedure of this test generally involves GH measurement every 30 min (30’) from baseline to +120’ or +180’. However, the optimal timing of samplings for the distinction between patients with or without active acromegaly is still a matter of debate. Methods Sixty-seven healthy subjects and 46 acromegalic patients who achieved documented and persistent long-term cure were enrolled. A greedy algorithm was used to identify the minimal subset of time-points that sufficed to correctly detect GH suppression. Results The sampling at 90’ was the one in which a GH level < 1 μg/L was most frequently achieved (i.e., in 91.3% of cured acromegalic patients and in 91.0% of healthy subjects). Considering the whole cohort, the best combination of 2 time-points was +90’ and +150’ and achieved 95.6% accuracy; the best combination of 3 time-points was +60’, +90’ and +150’ and achieved 99.1% accuracy. The minimal subset of GH determinations that demonstrated perfect accuracy (100%) needed the inclusion of 4 time-points, namely +60’, +90’, +120’ and +150’. Conclusion A subset of 4 time-points (60’ – 90’ – 120’ – 150’) was identified as the most relevant to detect GH suppression at OGTT, with a perfect classification of 100% of subjects. This supports the possibility to restrict the blood samplings to these time-points when assessing disease cure, with possible advantages in terms of saving time and lowering costs.