Prolactin levels in the insulin tolerance test with and without pre-treatment with dexamethasone

The serum prolactin response to insulin-induced hypoglycaemia was studied in 20 healthy volunteers. The results of insulin tolerance tests performed after pre-treatment with dexamethasone in a dose of 0.5 mg (0.5-DEX-ITT) and 1.0 mg (1.0-DEX-ITT) were compared with those of a similar control insulin tolerance test (ITT). The serum prolactin levels increased in all but 3 ITT's. In the ITT and 0.5-DEX-ITT the prolactin responses were significantly greater in women than in men. After pretreatment with dexamethasone the basal serum prolactin levels and the prolactin response to hypoglycaemia were significantly decreased compared with those in the ITT. The prolactin response both to insulin-induced hypoglycaemia and to dexamethasone showed such a large individual variation that this type of response seems unsuitable for evaluation of the hypothalamo-pituitary function.