Follicle-Stimulating Hormone (FSH) - Serum

Description

A follicle-stimulating hormone (FSH) test measures the level of this hormone in a sample of your blood. A hormone is a chemical messenger in your bloodstream that controls the actions of certain cells or organs. FSH plays an important role in sexual development in children and fertility in adults.

• In women who menstruate (have periods), FSH helps control the menstrual cycle. It triggers the growth of eggs in the ovaries and gets the eggs ready for ovulation. Ovulation is when an ovary releases an egg so it can travel down a fallopian tube where it can be fertilized by sperm.
• In men, FSH helps control the amount of sperm that the testicles (testes) make. It also affects how healthy the sperm are.
• In children, FSH levels are normally low until puberty starts. Then FSH levels begin to rise along with the levels of other hormones. The increase in all these hormones triggers the physical changes of puberty:
  • In girls, FSH tells the ovaries to start making the hormone estrogen. Estrogen is involved in the growth of breasts, body hair, and menstruation.
  • In boys, FSH tells the testicles to start making the hormone testosterone. Testosterone is involved in the growth of facial and body hair, changes in a boy's voice, and sperm production.

FSH levels are controlled by a complex system of hormones made in different parts of your body. Abnormal levels of FSH may be a sign of a problem with any of these parts. They include your:

• Pituitary gland, a small gland at the base of your brain. It makes FSH.
• Hypothalamus, a part of your brain. It makes hormones that tell your pituitary gland how much FSH to make.
• Reproductive glands, your ovaries or testicles. The amount of sex hormones they make let your hypothalamus and pituitary gland know when to start and stop making FSH.

Other names: follitropin, FSH, follicle-stimulating hormone: serum, pituitary gonadotropins.

Source: National Institutes of Health (NIH) U.S. Department of Health and Human Services.