Ovarian hyperandrogenism may induce adrenal enzymatic defects that mimic true inherited disorders of adrenal hormone biosynthesis. To assess the effect of hyperandrogenism on adrenal steroidogenesis, seven normal ovulatory women were studied on 2 days during the early follicular phase of their cycles. Plasma 17-hydroxyprogesterone (17-Prog), 17-hydroxypregnenolone, dehydroepiandrosterone (DHEA), DHEA sulfate, androstenedione (Adione), testosterone (T), 11-deoxycortisol, and cortisol concentrations were measured every 15 min for 3 h after iv injection of 0.25 mg ACTH (day 1) and pretreatment with dexamethasone on each day. On the second study day, T (80 micrograms/h) was infused iv for 5 h, and ACTH was given after 2 h of T infusion. The T infusion raised mean serum T levels from 1.2 +/- 0.3 (+/- SE) to 8.6 +/- 0.6 nmol/L. The maximum incremental (delta max) plasma Adione response to ACTH was significantly higher (2.6 +/- 0.3 to 3.2 +/- 0.4 nmol/L; P less than 0.009) during the T infusion, while the delta max responses of the other steroids did not change. There was an increase in the delta max 17-Prog to cortisol ratio (4.9 +/- 0.7 to 7.0 +/- 1.0; P less than 0.05), but no change in the delta max 17-Prog to Adione or 17-hydroxypregnenolone to DHEA ratios and no changes in the delta max delta 5- to delta 4-steroid ratios. These data suggest that acute T elevations result in subtle inhibition of 21-and/or 11 beta-hydroxylase activities, but not in 17-20-desmolase or 3 beta-ol activities.