Medical Health Encyclopedia

Reproductive Hormones. The hypothalamus (an area in the brain) and the pituitary gland regulate the reproductive hormones. The pituitary gland is often referred to as the master gland because of its important role in many vital functions, many of which require hormones. In women, six key hormones serve as chemical messengers that regulate the reproductive system:

Click the icon to see an image of the hypothalamus.

• The hypothalamus first releases the gonadotropin-releasing hormone (GnRH).
• This chemical, in turn, stimulates the pituitary gland to produce follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
• Estrogen, progesterone, and the male hormone testosterone are secreted by the ovaries at the command of FSH and LH and complete the hormonal group necessary for reproductive health.

Click the icon to see an image of the pituitary gland.

Ovulation. The process leading to fertility is very intricate. It depends on the healthy interaction of two sets of organs and hormone systems in both the male and female. In addition, reproduction is limited by the phases of female fertility. Nevertheless, this astonishing process results in conception within a year for about 80% of couples. Only 15% conceive within a month of their first attempts, however, and about 60% succeed after 6 months.

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A woman's ability to produce children occurs after she enters puberty and begins to menstruate. The process to conception is complex:

• With the start of each menstrual cycle, follicle-stimulating hormone (FSH) stimulates several follicles to mature over a two-week period until their eggs nearly triple in size. Only one follicle becomes dominant, however, during a cycle.
• FSH signals this dominant follicle to produce estrogen, which enters the bloodstream and reaches the uterus. There, estrogen stimulates the cells in the uterine lining to reproduce, therefore thickening the walls.
• Estrogen levels reach their peak around the 14th day of the cycle (counting days beginning with the first day of a period). At that time, they trigger a surge of luteinizing hormone (LH).