Amenorrhea is the absence of a menstrual period in a woman of reproductive age. Physiological states of amenorrhoea are seen, most commonly, during pregnancy and lactation (breastfeeding). Outside the reproductive years, there is absence of menses during childhood and after menopause.Amenorrhoea is a symptom with many potential causes. Primary amenorrhea is defined as an absence of secondary sexual characteristics by age 13 with no menarche or normal secondary sexual characteristics but no menarche by 15 years of age. It may be caused by developmental problems, such as the congenital absence of the uterus, failure of the ovary to receive or maintain egg cells, or delay in pubertal development. Secondary amenorrhoea, ceasing of menstrual cycles after menarche, is defined as the absence of menses for three months in a woman with previously normal menstruation, or six months for women with a history of oligomenorrhoea. It is often caused by hormonal disturbances from the hypothalamus and the pituitary gland, premature menopause, intrauterine scar formation, or eating disorders. Pathophysiology
Although amenorrhea has multiple potential causes, ultimately, it is the result of hormonal imbalance or an anatomical abnormality.Physiologically, menstruation is controlled by the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus. GnRH acts on the pituitary to stimulate the release of follicle stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH then act on the ovaries to stimulate the production of estrogen and progesterone which, respectively, control the proliferative and secretary phases of the menstrual cycle.
Although the exact mechanism still remains unknown, it is hypothesized that this is due to metformins ability to increase the bodys sensitivity to insulin. Anti-androgen medications, such as spironolactone, can also be used to lower body androgen levels and restore menstruation. Oral contraceptive pills are also often prescribed to patients with secondary amenorrhea due to PCOS in order to regularize the menstrual cycle, although this is due to the suppression of ovulation. References
External links

Disability Onlines amenorrhoea page
Disability Onlines athletic amenorrhoea page
Amenorrhea