Estrogen produced in the brain is necessary for ovulation in monkeys, according to researchers at the University of Wisconsin–Madison who have upended the traditional understanding of the hormonal cascade that leads to release of an egg from the ovaries.
Their findings, published Dec. 11 in the journal Proceedings of the National Academy of Sciences, may reveal the cause of some undiagnosed infertility problems and point the way to new methods of birth control.
For decades, scientists have known that a group of neurons in a part of the brain called the hypothalamus and cells in the pituitary gland control the menstrual cycle. The brain stimulates the pituitary to make hormones that, early in the menstrual cycle, spur the ovaries to produce estrogens — predominantly a type of estrogen called estradiol.
Estradiol builds in the bloodstream until it reaches a concentration that causes a surge of the hypothalamic and pituitary hormones, including one called luteinizing hormone, which in turn trigger an ovary to release an egg.