Follicle stimulating hormone, or FSH, is a hormone secreted by the pituitary gland that plays a critical role in the reproductive process for both sexes. In women, FSH stimulates the ovaries to release an egg each month, while in men it helps to regulate sperm production. Normal levels of FSH and pregnancy are closely tied together, as without FSH, no egg would be present for fertilization and sperm could not be produced to fertilize it. High levels of FSH are often indicative of fertility problems, as this typically means that women have fewer viable eggs available to release and men have testicular damage or failure.
The main way FSH and pregnancy are related is through the hormone's role in the production of the gametes, or sex cells. For women, it is essential for the process of ovulation; at a certain point in a woman's menstrual cycle, the brain recognizes that it is time for an egg to be produced and it stimulates the pituitary to release FSH, which in turn triggers one of the ovaries to cause a follicle to mature and release the resulting egg. Once this occurs, there is a window of opportunity for the woman to become pregnant. FSH and pregnancy are also connected because the hormone is critical for the production of sperm. The presence of normal FSH levels in a man's body stimulates the testicles to produce enough sperm to make fertilization likely when an egg is present.
Elevated levels of FSH and pregnancy are also closely connected, as higher than normal amounts of the hormone typically mean the person will experience infertility issues. FSH in women is produced based on feedback from the ovaries. The hormone prompts the ovaries to mature and release an egg, and if there is a lack of viable eggs to produce, the pituitary will put out more and more FSH until one can be produced.
Older women or women with abnormally depleted ovarian reserves may find that they often have increased FSH levels, and women who have gone through menopause and can no longer ovulate have permanently elevated levels. In men, high levels of FSH often mean the testicles have been damaged or have failed and are not working correctly. This usually means they will produce little to no sperm, making it difficult for a pregnancy to be achieved.