Congenital Adrenal Hyperplasias (CAH) are genetic diseases transmitted in an autosomal recessive way and these diseases affect many aspects of human health. The majority of CAH cases is due to a deficiency in 21-hydroxylase as a result of the existence of mutations in both alleles of the CYP21A2 gene. Since the identification of mild, non-classic forms of this disease, CAH has been recognized to be one of the most common genetic diseases in human beings.
This disease is generally associated with elevated secretion of androgens, sometimes resulting in virilizing syndromes, including genital ambiguity, precocious puberty in both sexes, or milder syndromes of androgen excess like precocious pubarche or the occurrence of hirsutism and oligomenorrhea in women. Accumulating precursors like 17-hydroxypregnenolone and 17-hydroxyprogesterone (17OHP) are directed to the synthesis of androgens through the enzyme 17-hydroxylase/17,20 lyase leading to the production of dehydroepiandrosterone that is then converted to testosterone and dihydrotestosterone (DHT) at the gonads and at other peripheral tissues. 17OHP, the hallmark of 21-hydroxylase deficiency, can be converted to androstenedione (in a low efficiency molecular process) but can also be converted to DHT through an alternative pathway that becomes active due to the large amounts of accumulated 17OHP – the backdoor pathway. Another important pathway that becomes significant in this disease is the 11-oxyandrogens pathway through which androstenedione is converted to 11β-hydroxyandrostenedione at the adrenal and from there to 11-ketotestosterone and 11-ketoDHT. The elevated androgens levels affect the hypothalamic-pituitary-gonadal axis and, in some cases, the ovary resulting in chronic anovulation and infertility.