Among the most common causes of female infertility, anovulation, menstrual irregularity, hirsutism, acne, and alopecia are congenital adrenal hyperplasia (CAH) and polycystic ovarian syndrome (PCOS). These two conditions resemble one another quite a bit, especially the nonclassic forms of CAH (NCAH). Another common cause of such problems is hyperprolactinemia, which results in increased androgen synthesis by both the ovaries and the adrenal cortex, while suppressing gonadotrophin-releasing hormone, gonadotrophin, and estrogen synthesis. Hyperprolactinemia, in turn, may be caused by primary hypothyroidism, prolactinomas, stalk effects of other pituitary and hypothalamic neoplasia, as well as a host of prescription and recreational drugs; it may also be idiopathic. Other, less frequently encountered causes of these problems include Cushing's syndrome and virilizing tumors (ovarian, adrenal, or ectopic). A growing worldwide problem in this sphere is androgen doping to improve athletic performance. Additional causes of menstrual irregularity include uterine leiomyomata, puberty, perimenopause, chronic illnesses eg. poorly controlled diabetes mellitus and sickle cell disease, elite athletics and dancing, eating disorders, endometriosis, and Asherman's syndrome. Infertility may also be caused by stress, tubal factors, Asherman's syndrome, immune response to spermatozoa, luteal phase inadequacy, and male factors. In this chapter we shall focus on 3 novel concepts: • The treatment of the congenital adrenal hyperplasias and the acquired/unmasked adrenal hyperplasias by interventions which reduce insulin resistance.