Production rates for testosterone were determined in seven healthy men before and during a euglycemic clamp using a stable labeled tracer (1alpha,2alpha-D-testosterone 0.13 +/- 0.04 mg/h) and analysis by gas chromatography-mass spectrometry (GC-MS). Following an equilibration period of 12 hours (8 PM to 8 AM), blood samples obtained at 20-minute intervals from 8 AM until 2 PM were subsequently pooled and evaluated for three 2-hour periods. Following determination of basal endogenous production (8 AM to 10 AM), the investigation was continued during two 2-hour periods of induced euglycemic hyperinsulinemia (10 AM to 2 PM). Production rates for testosterone (basal, 245 +/- 91 microg/h) remained unchanged during the first (234 +/- 87 microg/h) and second (207 +/- 94 microg/h) period of this euglycemic clamp. These results suggest that short-term hyperinsulinemia has no effect on endogenous production rates of testosterone in healthy men.