What physiological changes occur in the menopausal transition?

The physiological changes that occur during menopausal transition begin with your ovaries producing fewer eggs. Eventually, the ovaries no longer release eggs into the fallopian tubes and your menstrual cycle ends. You will have a drop in the female hormones estrogen and progesterone.

Low estrogen levels may cause hot flashes, night sweats, and vaginal dryness and irritation. You may also experience discomfort or pain during sex and lose your desire for sex. You can also experience memory loss, hair thinning and depression during the menopause transition.

When doctors talk about the physiological changes that occur during menopause we are talking about changes in how the body functions. So let's step back to the time before menopause. After puberty there is a team of hormones that sends a signal to an egg in the ovaries to mature into a follicle, which causes it to make estradiol, a type of estrogen. This ovulation happens every 28 days or so. If the egg doesn't get fertilized, it exits in the form of a monthly period. After a certain age, the eggs stop maturing and estrogen levels start to decline. And since estrogen has a big job in the body besides preparing the eggs for fertilization, less of it produced in the ovaries means less of it gets to the brain, blood vessels, bone, skin, heart, uterus, lungs, intestines and breasts. If estrogen doesn't get to these cells physiological changes occur. That's what causes hot flashes, night sweats, loss of bone, and vaginal dryness and vaginal tissue thinning. This menopausal transition can last a few years before it is completed. Menopause symptoms usually wane after a few years, although some women can have disabling symptoms for longer.

Estradiol levels are associated with many physiologic functions in women, including fat deposition, glucose metabolism, bone metabolism, blood clotting, and lipid metabolism. These factors, in turn, have been associated with potential risk for some diseases of advanced age, such as heart disease, diabetes, and osteoporosis.

Adipose (fat) tissue deposits are influenced by estradiol. During adolescence, estradiol causes fat deposits on the thighs, buttocks and breast tissue of young women. Although obesity is becoming much more common among women in the United States, evidence that women gain weight because of the menopausal transition is mixed. Women in the Healthy Women Study experienced an increase in waist circumference and upper body fat during the menopausal transition.

Blood insulin levels were highest in women with both a higher body mass index (BMI is higher among women who are heavier for their height) and increased abdominal fat. These factors are being tracked in the ongoing SWAN study. Early results suggest that estradiol levels are not associated with resistance to insulin (a body's failure to respond as usual to insulin). The forthcoming results of the SWAN study will help us understand the changes in metabolism across the menopausal transition and the development of diabetes.

Bone mass is constantly being built up and broken down. Since estradiol inhibits the breakdown of bone, there is concern that after menopause, women are at greater risk of losing bone mass. Indeed, women lose bone mass faster within the first three years following the final menstrual period than their reproductive years. One study indicated that women with higher estradiol and estrone levels have greater bone density, as do women who are overweight.

Estradiol promotes blood clotting, which can be good if you need to stop bleeding and heal, but can be dangerous if blood clots form in your leg veins or lungs (pulmonary emboli) and interfere with circulation, and even cause death. Effects of the menopausal transition on clotting are not yet clear. Estradiol is associated with increased secretion of lipoproteins, substances in the blood related to cholesterol and fat metabolism. It is also associated with lowered serum cholesterol and increased phospholipids levels.