Perimenopause, defined as the period of up to 10 years before menopause, is defined by hormonal changes that signal the shutting down of ovulation and the end of menstrual periods. One marker used to determine the onset of perimenopause is the level of follicle stimulating hormone (FSH) in the blood. Since FSH levels are linked to oestrogen production, fluctuating levels of these hormones result in menopausal symptoms such as breast tenderness and hot flushes.
Since perimenopause signals the end of reproductive life, hormones that trigger ovulation and the menstrual cycle undergo great shifts and become unbalanced. Menstrual cycles may become shorter or longer, periods may be heavier or lighter or are skipped altogether, until finally they completely shut down. These hormonal fluctuations cause the familiar symptoms of menopause such as breast tenderness, hot flushes, fatigue and mood swings.
FSH and the Menstrual Cycle
Follicle stimluating hormone (FSH) and luteinizing hormone (LH) are responsible for the menstrual cycle. In a regular cycle, FSH stimulates the ovaries to release an egg, or oocyte. Once that takes place, LH is released in the second half of the cycle, and if the egg is not fertilised, menstruation occurs on an average 28- to 30-day cycle. In perimenopause, ageing ovaries may not respond to normal levels of FSH, so the body produces more in an effort to stimulate ovulation. Testing for high FSH levels is one way to diagnose perimenopause.
FSH and Estrogen
The master hormone in the female reproductive system is oestrogen. This hormone stimulates the pituitary gland to produce FSH and begin ovulation. Fluctuations in oestrogen levels in perimenopause also cause changes in the production of FSH and other hormones in the reproductive cycle and, because these hormones circulate in the bloodstream, affect not only the reproductive system but the body as a whole.
Symptoms of High FSH Levels
Because changes in oestrogen levels and high FSH levels typically occur during perimenopause, a variety of symptoms typical of menopause are associated with the fluctuating levels of these hormones. Hot flushes, night sweats, vaginal dryness, headaches, irritability, mood swings and decreased libido are among the symptoms associated with high FSH levels, fluctuations in oestrogen levels and the overall onset of perimenopause.