What is FSH?

Follicle-stimulating hormone (FSH) is a hormone that plays a role in the regulation of sexual reproduction in both men and women. In addition to being involved in sexual reproduction, it also plays a role in the onset of puberty and menopause. Tests for levels of this hormone in the body are sometimes used to explore causes of infertility, and the diagnose the onset of menopause or puberty. FSH is also used in infertility treatments, in the form of injectable medications.

This hormone is in a class of compounds generated by the body known as gonadotropins. Gonadotropins are proteins, and they are produced by the section of the pituitary gland that is involved in the production of endocrine hormones. In women, FSH tells the follicles in the ovary to mature so that the woman can ovulate, releasing an egg into the uterus. Some doctors liken it to a gas pedal that is pushed by the anterior pituitary gland to start the engines of the ovarian follicles. In men, FSH is involved in sperm production.

As a general rule, FSH levels are low in childhood, because children need neither sperm nor eggs. At puberty, levels begin to increase, as the body prepares for sexual reproduction. In women, FSH levels are highest around the time of ovulation, and they will continue to rise into menopause, as more and more of the hormone is needed with each ovulation to stimulate the follicles into maturity, since fewer eggs are left.

When unusually high FSH levels are documented, it can be a sign that a woman is lacking viable eggs, which could contribute to fertility problems. High FSH in men is a sign that there is a problem with sperm production, and in both sexes, high levels have been linked with some other medical conditions as well. Extremely low FSH levels are linked with a decrease in the function of the gonads.

When women undergo fertility treatment because they are unable to conceive on their own, FSH injections are used to stimulate the follicles artificially. Using this hormone ensures that the process is more controlled, and allows medical professionals to increase levels in the hopes of getting at least one viable egg so that they can sweep in at the perfect moment to retrieve eggs. However, as many infertile women are aware, FSH injections are only one stage in a very long process, and they do not always work; the course of injections may have to be repeated several times before success is achieved.