Thermoregulatory responses to hyperinsulinaemic hypoglycaemia and euglycaemia in IDDM.

In healthy subjects hypoglycaemia causes a fall in body temperature through increased sweating and limb blood flow, and despite increased metabolic heat production. We studied thermoregulatory responses to hyperinsulinaemic (100 mU.m-2.min-1) (a) hypoglycaemia (2.5 mmol/l) and (b) euglycaemia (4.5 mmol/l) in insulin-dependent diabetic men of short (< 5 years) and long (> 15 years) diabetes duration. Plasma noradrenaline (p < 0.0001), metabolic rate (p < 0.005), heart rate (p < 0.0001) and skin blood flow (p < 0.05) increased during hypoglycaemia and euglycaemia with a greater rise in noradrenaline during the former (p < 0.05). Plasma adrenaline (p < 0.005), forearm blood flow (p < 0.05) and systolic blood pressure (p < 0.02) increased and diastolic blood pressure decreased (p < 0.005) during hypoglycaemia, with greater changes in adrenaline (p < 0.05) and diastolic blood pressure in patients of short diabetes duration. Only two patients (diabetes duration < 2 years) sweated appropriately, while body temperature changed minimally in the two groups of patients. In summary, thermoregulatory responses to hypoglycaemia are impaired in IDDM due to attenuated sweating and adrenomedullary responses.