The role of PRL in the secretion of androgens by the adrenal glands was investigated in vivo and in vitro. In women with hyperprolactinemia whose pituitary-adrenal function was normal, there was significant correlation between serum PRL and dehydroepiandrosterone sulfate [(DHEA-S) gamma = 0.48, P less than 0.05, n = 34] and DHEA (gamma = 0.50, P less than 0.05, n = 34), but not with androstenedione. Long term administration of sulpiride to normal women increased both serum PRL and DHEA-S, whereas acute elevation of PRL after a single iv dose of domperidone had no influence on the serum DHEA-S levels. Monolayer cultures of human adrenal cells were used in order to study the direct effect of PRL on adrenal androgen secretion. The daily secretion of DHEA-S, DHEA, androstenedione, and cortisol was determined. In the absence of ACTH, PRL had no effect on steroid secretion in a 7-day culture period. In the presence of ACTH, there was a daily increase in the secretion of steroids. PRL, when added in combination with ACTH, potentiated the effect of ACTH on DHEA-S and DHEA but not on androstenedione and cortisol secretion on the seventh day in culture. These results indicate that PRL has a direct synergistic effect with ACTH on adrenal cells to increase adrenal androgen release. Increases in DHEA-S and DHEA but not androstenedione in vitro and correlation between serum PRL and DHEA-S and DHEA but not androstenedione in women with hyperprolactinemia suggest that the synergistic effect of PRL on adrenal androgen secretion may result from partial inhibition of adrenal 3 beta-hydroxysteroid dehydrogenase.