This test measures the level of follicle-stimulating hormone (FSH) in your blood. FSH is made by your pituitary gland, a small gland located underneath the brain. FSH plays an important role in sexual development and functioning.
In women, FSH helps control the menstrual cycle and stimulates the growth of eggs in the ovaries. FSH levels in women change throughout the menstrual cycle, with the highest levels happening just before an egg is released by the ovary. This is known as ovulation.
In men, FSH helps control the production of sperm. Normally, FSH levels in men do not change very much.
In children, FSH levels are usually low until puberty, when levels begin to rise. In girls, it helps signal the ovaries to make estrogen. In boys, it helps signal the testes to make testosterone.
Too much or too little FSH can cause a variety of problems, including infertility (the inability to get pregnant), menstrual difficulties in women, low sex drive in men, and early or delayed puberty in children.
Other names: follitropin, FSH, follicle-stimulating hormone: serum
FSH works closely with another hormone called luteinizing hormone to control sexual functions. So a luteinizing hormone test is often done along with an FSH test. These tests are used in different ways, depending on whether you are a woman, man, or child.