Estrogen maintains fertility in women and regulates energy balance. After menopause, when the ovaries stop making estrogen, women tend to gain weight, which may lead to metabolic syndrome and type 2 diabetes. Estrogen exerts it effect by binding to specific estrogen receptors in the ovaries, uterus, fat, and muscles. Now a new study traced the effect of weight control to estrogen receptors in the brain. When brain estrogen receptors were deleted in mice, the mice became fat. The studies also suggested that fertility and problems with ovulation are controlled by brain estrogen receptors.
How estrogen works
Estrogen refers to a group of related chemicals, or hormones, that are produced in the body by the ovaries, adrenal glands, and fat tissue. Estrogens need to bind to estrogen receptors in different parts of the body to activate genes. Estrogen-activated genes help develop female organs, cause ovulation, maintain bone strength, and maintain a normal pregnancy.
Weight gain
Women with slim figures and no change in their diet, often become plump at menopause. Studies showed that the drop in estrogen causes an increase in appetite and lowers metabolism. Animal studies found that signaling by an estrogen receptor by binding to estrogen or even to an anti-estrogen could reduce appetite and increase metabolism.
Infertility
Estrogen thickens the lining of the uterus during the first part of the menstrual cycle. An insufficient amount of estrogen results in a thin lining and prevents implantation of a fertilized egg. Estrogen also regulates ovulation, the release of an egg from the ovaries. Insufficient estrogen reduces ovulation and causes irregular periods. Both insufficient estrogen as well as too much estrogen, sometimes called “estrogen dominance”, can cause infertility. Too much estrogen can reduce infertility, because it can cause ovarian cysts, uterine fibroids and endometriosis.
It’s all in the brain
When researchers removed all brain estrogen receptors in mice, all mice gained abdominal fat without a change in diet. The scientists then looked at estrogen receptors in different parts of the brain and found that estrogen receptors on some neurons, or nerve cells, regulated abdominal fat. The loss of these estrogen receptors caused the mice to become obese, while the loss of estrogen receptors on other neurons in other parts of the brain did not cause obesity, but made the mice infertile.
Development of drugs or designer hormones could target brain estrogen receptors on the different type of neurons to prevent abdominal obesity, infertility, and maybe even hot flashes and memory loss in women without the use of estrogen. Exogenous estrogen may have serious side effects in postmenopausal women.
Sources
Xu, Y. et al. Distinct Hypothalamic Neurons Mediate Estrogenic Effects on Energy Homeostsis and Reproduction. Cell Metabolism (2011) 14: 453
http://www.sciencedaily.com/releases/2011/10/111004123600.htm
http://www.mayoclinic.com/health/belly-fat/WO00128