FSH
Also called Follicle-stimulating hormone, follitropin
FSH (follicle-stimulating hormone) is a hormone made by the pituitary gland, at the base of the brain, that controls key parts of reproduction. In women it triggers the growth of eggs in the ovaries and helps run the menstrual cycle; in men it helps control how much sperm the testicles make and how healthy that sperm is.
FSH sits in a feedback loop with the hypothalamus, the pituitary and the ovaries or testicles. When the ovaries or testicles make less of their own hormones, the pituitary usually responds by making more FSH, so an FSH result helps show whether a problem starts in the glands themselves or in the brain signals that drive them. It is usually read alongside LH (luteinizing hormone).
Why it matters after 45
In women, rising FSH is a normal sign of perimenopause and menopause, as the ovaries release fewer eggs and the body makes more FSH to try to trigger ovulation. MedlinePlus notes that for women aged 45 or older, testing usually is not needed to confirm this. In men, the Endocrine Society recommends measuring LH and FSH when testosterone is low, to tell testicular causes apart from pituitary or hypothalamic ones, and FSH also comes up in fertility testing.
Where it comes up
- Am I in perimenopause?how the transition is recognized, with or without a blood test
- When to test hormones in perimenopausewhy FSH swings during the transition
- Male fertility testthe semen analysis that hormone results are read beside
- TRT and fertility FAQhow testosterone therapy and fertility interact
Related terms
References
- MedlinePlus. Follicle-Stimulating Hormone (FSH) Levels Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/follicle-stimulating-hormone-fsh-levels-test/
- Cleveland Clinic. Follicle-Stimulating Hormone (FSH). https://my.clevelandclinic.org/health/articles/24638-follicle-stimulating-hormone-fsh
- Endocrine Society. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline, 2018. https://www.endocrine.org/clinical-practice-guidelines/testosterone-therapy
Definitions here are educational and are not medical advice. They explain what a term means; the pages linked above cover what it means for you, and a clinician reviews your own results. Editorial & medical review policy · All glossary terms