Objective: This study sought to examine corticosteroidogenic enzyme activities in normo-and hyperandrogenic polycystic ovary syndrome (PCOS) patients. Subjects and methods: This cohort study included 81 patients with biochemical hyperandrogenism and 41 patients with normal androgen levels. Enzyme activities were assessed according to the serum steroid product/precursor ratios at baseline and after adrenal stimulation. Results: At baseline, in the delta 4 (Δ4) pathway, hyperandrogenic patients showed greater 17-hydroxylase and 17,20 lyase activities in converting progesterone (P4) into 17-hydroxyprogesterone (17-OHP4) and 17-hydroxypregnenolone (17-OHPE) into androstenedione (A) (p = 0.0005 and p = 0.047, respectively) compared to normoandrogenic patients. In the delta 5 (Δ5) pathway, the 17-hydroxylase and 17,20 lyase enzymes showed similar activities in both groups. Hyperandrogenic patients presented lower 21-hydroxylase, lower 11β-hydroxylase (p = 0.0001), and statistically significant increases in 3β-hydroxysteroid dehydrogenase II (3β-HSDII) activities (p < 0.0001). Following tetracosactrin stimulation, only the 17,20 lyase activity remained up--regulated in the Δ4 pathway (p < 0.0001). Conclusion: Hyperandrogenic patients had higher 17,20 lyase activity, both at baseline and after adrenal stimulation. Greater conversion of dehydroepiandrosterone (DHEA) into A with normal conversion of 17-OHPE to 17-OHP4 in hyperandrogenic PCOS patients indicated different levels of 3β-HSDII activity in adrenal cells, and hyperandrogenic patients had lower 11β-hydroxylase and 21-hydroxylase activities. Arq Bras Endocrinol Metab. 2013;57(6):437-44 Keywords Polycystic ovary syndrome; steroidogenesis; hyperandrogenism; enzyme activity; adrenal stimulation RESUMO Objetivo: O objetivo deste estudo foi examinar a atividade de enzimas responsáveis pela produção de corticosteroides em pacientes normo e hiperandrogênicas com síndrome de ovários policísticos (SOP). Sujeitos e métodos: A coorte estudada incluiu 81 pacientes com hiperandrogenismo bioquímico e 41 pacientes com níveis normais de androgênio. A atividade enzimática foi avaliada de acordo com as proporções de produto/precursor do esteroide sérico, no momento inicial do estudo e depois de estimulação adrenal. Resultados: No momento inicial, na via delta 4 (Δ4), as pacientes hiperandrogênicas mostraram maior atividade da 17-hidroxilase e 17,20 liase na conversão da progesterona (P4) em 17-hidroxiprogesterona (17-OHP4) e na conversão da 17-hidroxipregnenolona (17-OHPE) em androstenediona (A) (p = 0,0005 e p = 0,047, respectivamente) em comparação com pacientes normoandrogênicas. Na via delta 5 (Δ5), a 17-hidroxilase e a 17,20 liase mostraram atividades similares nos dois grupos. As pacientes hiperandrogênicas mostraram menor atividade da 21-hidroxilase, menor atividade da 11β-hidroxilase (p = 0,0001) e aumento estatisticamente significativo na atividade da 3β-hidroxiesteroide desidrogenase II (3β-HSDII) (p < 0.0001). Após a estimulação com tetracosactrin, apenas a ativi...