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 -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="">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="">P<0.001; aucb="421.22±4.31" mu/l="" vs="" 712.20±3.42="">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="">