GLUCOSE-TOLERANCE, INSULIN-SECRETION, INSULIN SENSITIVITY AND GLUCOSEEFFECTIVENESS IN NORMAL AND OVERWEIGHT HYPERTHYROID WOMEN

OBJECTIVE Inter-relationships between insulin sensitivity and body wei ght in patients with hyperthyroidism remain incompletely understood. W e have examined whether a mild excess of body weight exacerbates the m etabolic abnormalities of spontaneous hyperthyroidism. DESIGN AND PATI ENTS Insulin-modified intravenous glucose tolerance tests were perform ed on 14 hyperthyroid women with body mass indices (BMI) ranging from 21 to 31 kg/m(2). A control group of 10 healthy women matched for age and BMI was also studied. MEASUREMENTS Intravenous glucose tolerance ( KG), first and second-phase integrated insulin responses to glucose, t he integrated glucose area under the curve (AUC), and minimal model pa rameters of insulin sensitivity (SI) and glucose effectiveness (SG) we re determined. RESULTS Hyperthyroid women had mean KG, glucose-induced insulin secretion and SG values similar to those in control women. Th e mean glucose AUC was higher in hyperthyroid patients (P < 0.05). Low er insulin sensitivity was observed in hyperthyroid patients than in c ontrol women (SI = 0.38 +/- 0.07 vs 0.59 +/- 0.07 l/min pmol 10(4) (me an +/- SEM), P < 0.05). A steeper decline in insulin sensitivity with increase in body mass index was found in hyperthyroid women when compa red with the control group, after adjusting for age. When groups were compared according to their BMI, hyperthyroid women with normal weight (BMI less than or equal to 25 kg/m(2), n = 8) had mean KG, insulin re sponse to glucose, glucose AUC, SG and SI values similar to those in n ormal weight control women (n = 11). Overweight hyperthyroid patients (BMI > 25 kg/ m(2), n = 6) had a higher (P < 0.05) second-phase insuli n response to glucose than normal weight patients, a higher glucose AU C (P < 0.05) than normal weight patients and overweight controls (n = 8), and a lower SI (P < 0.05) than normal weight patients and overweig ht controls. SG was not influenced by BMI in hyperthyroid patients. CO NCLUSIONS These results suggest that overall glucose tolerance was not significantly affected in normal weight hyperthyroid women. However, when a moderate excess of weight is also present, a state of clear ins ulin resistance occurs.