Suppression of serum insulin level by diazoxide does not alter serum testosterone or sex hormone-binding globulin levels in healthy, nonobese women. Suppression of serum insulin levels with diazoxide is associated with a decrease in serum testosterone and an increase in serum sex hormone-binding globulin in obese women with the polycystic ovary syndrome. To determine whether physiologic insulin levels play a regulatory role in the androgen status of nonobese women with normal menses, the androgen status of five nonobese normal women was assessed on two occasions: during a control study and after 10 days of oral diazoxide (100 mg, three times daily) administration. Insulin release in response to 100 gm oral glucose administration decreased from 108.0 +/- 28.2 to 49.3 +/- 5.2 nmol.min/L (p = 0.05) after diazoxide administration. However, despite suppression of insulin release, diazoxide administration did not affect serum total testosterone (diazoxide, 0.73 +/- 0.10; control, 0.69 +/- 0.11 nmol/L; p = NS) or sex hormone-binding globulin (diazoxide, 79.7 +/- 16.6; control, 70.2 +/- 12.6 nmol/L; p = NS) concentrations. These observations suggest that physiologic insulin levels in nonobese healthy women do not regulate testosterone metabolism and that diazoxide does not exert a direct or independent effect on serum testosterone or sex hormone-binding globulin levels. 