Objective: To summarize available data concerning adrenal hyperandrogenemia caused by 21-hydroxylase deficiency, non-classic adrenal hyperplasia (NCAH). Design: Review article. Setting: Department of Gynecology and Obstetrics, General Faculty Hospital and 1st Medical Faculty, Prague. Methods: Compilation of published data from scientific literature. Conclusion: Although 21-hydroxylase deficiency is one of the most frequent autosomal recessive genetic disorders, prevalence of NCAH in the whole population and among hyperandrogenic women is very low. The measurement of 17OH-progesterone should be incorporated into the standard evaluation of all hyperandrogenic patients to establish or exclude the diagnosis of NCAH. There is no typical clinical sign of NCAH, and clinical symptoms are to similar to patients with PCOS. Corticoid substitution as a treatment modality of NCAH is derived from therapy of classic congenital adrenal hyperplasia (CAH). Antiandrogen therapy is effective in skin disorders (hirsutism). Due to normal cortisol value there is to use of combined oral contraceptives in the treatment of choice. An improvement of clinical symptoms is a key parameter for the evaluation of treatment effectiveness. There are no data about risk of late metabolic complications in NCAH patients.

        Key words: classic adrenal hyperplasia (CAH), non-classic adrenal hyperplasia (NCAH), polycystic ovary syndrome, 17OH-progesterone, corticoids