ECEESPE2025 ePoster Presentations Growth Axis and Syndromes (132 abstracts)
Insulin tolerance test for the diagnosis of adult GH deficiency: definition of BMI-dependent cut-offs using a clinical gold standard
Daniela Cuboni 1 , Michela Sibilla 1 , Francesca Mocellini 1 , Luigi Simone Aversa 1 , Emanuele Varaldo 1 , Fabio Bioletto 1 , Alessandro Maria Berton 1 , Nunzia Prencipe 1 , Mauro Maccario 1 , Ezio Ghigo 1 , Silvia Grottoli 1 & Valentina Gasco 1
1Division of Endocrinology, Diabetes, and Metabolism, Department of Medical Science; University of Turin;, Turin, Italy
JOINT2302
Background: The diagnosis of adult growth hormone deficiency (GHD) relies on demonstrating a reduced growth hormone (GH) response to stimulation tests. Excess body weight, a condition with increasing prevalence in the general population, is known to blunt GH secretion across all stimulation tests. Consequently, establishing BMI-specific normality cut-offs is essential to ensure accurate interpretation of somatotropic axis function. However, no validated BMI-adjusted cut-offs currently exist for the insulin tolerance test (ITT), the gold standard for GHD diagnosis. This study aimed to define BMI-dependent ITT cut-offs using a clinical criterion as the diagnostic gold standard, addressing key methodological limitations in previous research.
Subjects and Methods: We conducted a retrospective analysis of 105 patients with hypothalamic-pituitary disorders who underwent ITT at our center between January 1, 2021, and September 30, 2024. GHD was defined by the presence of at least three pituitary hormone deficiencies (MPHD), while preserved somatotropic function was established by the absence of other pituitary deficits and an IGF-I SDS ≥ 0. ITT was performed using a standardized protocol. ROC curve analysis was applied to determine optimal BMI-specific cut-off values, defined as those achieving the best sensitivity (SE) and specificity (SP).
Results: The optimal GH cut-off for diagnosing GHD was 2.8 μg/L in normal-weight and overweight subjects (normal-weight: SE 84.6%, SP 97.4%; overweight: SE 100%, SP 92.3%), while for obese individuals, the optimal threshold was lower at 2.1 μg/L (SE 88.2%, SP 87.5%). The area under the ROC curve values were 0.968, 0.957, and 0.897 for normal-weight, overweight, and obese patients, respectively, demonstrating high diagnostic accuracy across BMI categories.
Discussion: This study is the first to establish BMI-specific GH cut-offs for ITT using a clinical definition of GHD as the diagnostic gold standard. The findings reinforce the necessity of applying lower cut-offs in obese individuals to mitigate the risk of overdiagnosis and avoid unnecessary GH replacement therapy. Implementing BMI-adjusted thresholds in clinical practice could enhance diagnostic precision, ensuring that treatment is appropriately targeted to those who will benefit most.
Volume 110
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Endocrine Abstracts
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