A Reappraisal of Diagnosing GH Deficiency in Adults: Role of Gender, Age, Waist Circumference, and Body Mass Index

Objective: The objective of the study was to reevaluate the diagnostic accuracy of GH peak after GHRH plus arginine test (GHRH + ARG) according to patients' age, body mass index (BMI), and waist circumference to diagnose GH deficiency (GHD). Outcome Measures: GH peak after GHRH + ARG and IGF-I levels reported as SD score. Subjects: Subjects included 408 controls (218 women, 190 men, aged 15-80 yr) and 374 patients with hypopituitarism (167 women, 207 men, aged 16-83 yr). Results: In the (elderly) healthy subjects 15-25 yr old (young), 26-65 yr old (adults) and older than 65 yr, GH cutoffs were 15.6, 11.7, and 8.5 mu g/liter, 11.8, 8.1, and 5.5 mu g/liter, and 9.2, 6.1, and 4.0 mu g/liter, respectively, in the lean, overweight, and obese subjects. Waist circumference was the best predictor of GH peak (t = -7.6, P < 0.0001) followed by BMI (t = -6.7, P < 0.0001) and age (t = -5.7, P < 0.0001). Based on the old (<9.1 mu g/liter) and new GH cutoff, 286 (76.5%) and 276 (73.8%) of 374 hypopituitary patients had severe GHD. The receiving-operator characteristic analysis showed GH cutoffs in line with the third percentile or slightly higher results so that the prevalence of GHD increased to 90.1%. Conclusions: The results of the current study show that waist circumference and BMI are the strongest predictors of GH peak after GHRH + ARG followed by age. However, the old cutoff value of 9.0 mu g/liter was in line with the new cutoffs in 95% of patients. (J Clin Endocrinol Metab 94: 4414-4422, 2009)