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Menopause - The Physiological Basis For Menopause

Medicine EncyclopediaAging Healthy - Part 3Menopause - The Physiological Basis For Menopause, Sexuality During Menopause, Estrogen Replacement/hormonereplacement Therapy (hrt) And Androgen Replacement

The physiological basis for menopause

The effects of menopause are due to the loss of hormone production by the ovaries. Besides producing eggs over a woman's reproductive life span, the ovaries are also responsible for producing most of a woman's estrogen ("female" hormones) as well as half of her androgens, including testosterone ("male" hormones). Most symptoms of menopause are due to the loss of estrogen, though increasing attention is being paid to the effects of the loss of androgen production.

Menopause is not one moment in time, but rather a process called perimenopause that evolves over three to five years before the cessation of menses. During this time a woman's ovaries gradually become less responsive to stimulation from the central control of the pituitary gland at the base of the brain. Over this time, menstrual periods become gradually more irregular, both in timing and in flow. The pituitary gland at the base of the brain responds to circulating estrogen levels and the brain's hypothalamic stimulation by increasing secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH). Elevated levels of FSH are the cause of hot flushes.

Premenopausal women who have both ovaries removed, usually as part of a hysterectomy and bilateral oophorectomy, have a precipitous decline in their hormones and are suddenly thrust into the symptoms of menopause. The loss of ovarian function causes an 80 percent decrease in estrogen levels. The low levels remaining are produced by the adrenal glands, as well as by peripheral conversion of cholesterol to estrogen in the skin.

Estrogen has effects on many tissues in the body, especially the mucosal lining of the vagina. As estrogen levels drop, this lining thins, produces less lubrication, and becomes more vulnerable to trauma. The urethra is also affected by this increasing the chances of bladder infection and incontinence.

Ovarian testosterone production drops by half, starting as much as three years before a woman's final period. This decline can adversely affect overall mood and energy, as well contribute to decreased sexual desire. The ratio of androgens to estrogen can flip to androgen excess for some women, contributing to increases in hair growth in such "male" areas as the upper lip and chin.

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