Evaluation of growth hormone in thalassaemic boys with failed puberty: Spontaneous versus provocative test

Growth hormone (GH) secretion was determined by evaluating ultradian GH profiles for 12 h and GH responses to insulin stimulated hypoglycaemia (ITT) in 28 stunted boys with β-thalassaemia major aged 15.2–17.4 years, who presented with pubertal failure (FP). Healthy non thalassaemia prepubertal boys (n=10) aged 7.5–8.8 years, were studied as controls. All patients had normal responses to ITT with peak GH levels ≥15 mU/l. Basal GH concentrations (mean±sem) (1.65±0.03 mU/l vs 2.58±0.27 mU/l;P<0.05) and the stimulated GH responses (peak GH=15.4±0.20 mU/l vs 21.08±0.78 mU/l;P<0.001) were significantly lower in the patients with failed puberty than in the controls, indicating that the FP patients had diminished GH reserve and secretory capacity. Moreover, all the GH peak parameters including the maximum spontaneous concentrations (MX-GH) and the area under the GH curve (AUC) were significantly lower in the thalassaemic patients than in the controls (MX-GH=5.2±0.21 mU/l vs 20.42±0.14 mU/l;P<0.001; AUCb=421.22±4.31 mU/l vs 712.20±3.42 mU/l;P<0.001). These observations suggest that the thalassaemic patients had endogenous neurosecretory GH deficiency (GHND). Priming with sex steroid did not cause any improvement in the spontaneous or stimulated GH secretory patterns in thalassaemic patients. It was noteworthy that in neither the patients nor the control subjects, was there a significant correlation between the maximum stimulated and the MX-GH concentrations. These data suggest that the provocative ITT underestimates spontaneous GH secretion and that measurement of spontaneous GH secretion was a more reliable method for identifying patients with GH insufficiency than the ITT.