The insulin tolerance test after pre-treatment with dexamethasone.

The plasma 11-hydroxycorticosteroid and serum GH responses to insulin-induced hypoglycaemia were studied in 25 healthy volunteers. The results of a control insulin tolerance test were compared with those of 2 similar tests which were performed after pre-treatment with dexamethasone 0.5 and 1.0 mg, respectively. The GH response to hypoglycaemia was significantly lower in women than in men in all 3 tests. In men, but not in women, the GH response was lower after pre-treatment with 1 mg dexamethasone than in the other 2 tests. The plasma 11-hydroxycorticosteroid response was significantly greater after pre-treatment with 0.5 mg dexamethasone than in the control test, and was at least as good after 1 mg dexamethasone. After pre-treatment with dexamethasone the subjects experienced less discomfort and a shorter duration of sweating than in the control insulin tolerance test. Pre-treatment with 1 mg dexamethasone also has other advantages. Thus, the basal plasma cortisol level is low and stable, which facilitates estimation of the magnitude of the cortisol response. Furthermore, information is obtained about the dexamethasone suppression response.