Pub. date: 2008 | Online Pub. Date: April 21, 2008 | DOI: 10.4135/9781412963855 | Print ISBN: 9781412941860 | Online ISBN: 9781412963855| Publisher:SAGE Publications, Inc.About this encyclopedia
Menstruation and Premenstrual Syndrome
The menstrual cycle, also called the ovarian cycle, is the cyclical repeat preparation of the human female reproductive organs for conception. Menarche (the first menstrual period) generally occurs between the ages of 11 and 15. The menstrual/ovarian cycle continues until climacteric or menopause between the ages of 48 and 55. Each woman experiences variations in timing and duration of the cycle from 25 to 35 days, with an average of 28 days, with an average blood loss of 40 mL The severity of inconvenience and symptoms vary. The cycle is hormonally mediated with gonadotropic releasing hormone (GnRH), a hypothalamic hormone that in turn stimulates the pituitary to release follicle stimulating hormone (FSH). This binds to specific receptors on the follicular cells in the ovaries. Luteinizing hormone (LH) binds to plasma membrane receptors and stimulates the production of progesterone by corpus luteum cells. A feedback loop controls the release of GnRH, ...