FSH (Follicle-Stimulating Hormone)
Also written as: Follicle-stimulating hormone, Follitropin
A pituitary hormone that drives egg and sperm development; used to assess ovarian and testicular function.
What it measures
The level of follicle-stimulating hormone, a messenger released by the pituitary gland at the base of the brain. FSH tells the ovaries to mature eggs and the testes to make sperm, so it reflects the conversation between the brain and the reproductive glands.
Why a doctor orders it
Ordered for irregular or absent periods, fertility evaluations, questions about menopause timing, low testosterone work-ups in men, and early or delayed puberty. Comparing FSH with the hormones it stimulates helps locate where in the system a change is happening.
What is generally associated with a higher result
Broadly associated with reduced ovarian or testicular output, because the pituitary raises its signal when the reproductive glands respond less. It rises naturally with menopause.
What is generally associated with a lower result
Broadly associated with reduced signaling from the pituitary or hypothalamus, and with suppression by hormonal contraception, pregnancy, or significant physical stress such as intense training or low body weight.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- The day of the menstrual cycle on which blood was drawn
- Hormonal contraception, which suppresses it
- Pregnancy
- Recent significant weight loss or intense exercise
- Biotin supplements, which can interfere with some lab methods
Questions to take to your appointment
- Was this drawn on the right cycle day for the question being asked?
- Should this be interpreted together with LH and estradiol?
- Could my contraception have suppressed this result?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
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