Growth hormone nadir during oral glucose load depends on waist circumference, gender and age: normative data in 231 healthy subjects.

Objective  (i) To analyse the predictors of GH suppression after standard glucose load (oGTT) in the healthy population and (ii) to establish the 97th percentile of GH nadir post-oGTT according to these variables. Design  Analytical, retrospective. Measurements  GH nadir after oGTT. Subjects  Two hundred and thirty-one healthy subjects (113 women, 118 men 15-80 years) were studied. Results  The GH nadir after glucose load ranged from 0·01 (<assay detection limit) to 0·65 μg/l was higher in women and was inversely correlated with age, BMI, waist circumference, waist/hip, total cholesterol, triglycerides, basal and maximal glucose and basal insulin levels and directly correlated with basal GH levels, IGF-I SDS and HDL-cholesterol (P values ranging 0·004-<0·0001). On multistep regression analysis, the best predictors of nadir GH levels were waist circumference (t = -9·64, P < 0·0001), gender (t = -3·86, P = 0·0001) and age (t = -3·63, P = 0·0003). The results of comparative analysis among subjects grouped according to these variable showed different results in GH nadir in premenopausal women with waist circumference ≤88 cm (97th percentile 0·65 μg/l), in premenopausal women with waist circumference ≤88 cm and in men of any age with waist circumference ≤102 cm (97th percentile 0·33 μg/l) and in subjects of either gender and any age with waist circumference >88 cm in women and 102 cm in men (97th percentile 0·16 μg/l). Conclusions  The results of this study show that GH nadir after oGTT should be analysed according to gender, menopausal status and waist circumference. The GH cut-off should be limited to the assay used.