The phenotypes of the polycystic ovarian syndrome (PCOS) and congenital adrenal hyperplasia syndrome (CAHS) present a number of similarities. The main symptoms of PCOS are obesity, menstrual disorders, hirsutism, and low fertility in which the pituitary and adrenal glands are spared. The CAHS is a group of various entities all characterised by different degrees of malfunction of the 21-hydroxylase (CYP21) enzyme. The consequences are a downfall of the levels of aldosterone and cortisol, and the hyperproduction of adrenal androgen hormones. It is capital to be able to recognise these 2 entities in terms of identification of high risk families because the female foetuses suffering from CAHS will undergo severe virilization of there genitals in utero, which can efficiently be prevented by a administration of corticotherapy to the mother throughout the pregnancy.