Follicle stimulating hormone test (FSH test): a blood test that measures the level of follicle-stimulating hormone (FSH) in the blood. FSH is a hormone produced by the pituitary gland at the base of the brain. It helps regulate the menstrual cycle (your period) and the process of ovulation in women. FSH in men also helps with healthy sperm production. An FSH test can determine if your body is making too much or too little of the hormone and is often performed to help understand the cause of infertility.
J. Larry Jameson, et al. Harrison's Principles of Medicine. McGraw-Hill Professional Publishing Published: July 23rd 2018; Edition: 20.