- Made by
- Pituitary gland
- High FSH suggests
- Ovarian or testicular change
- Low FSH suggests
- Pituitary or hypothalamic cause
- Perimenopause
- Fluctuates; one test isn't conclusive
How FSH works
FSH works in a feedback loop with the ovaries or testes. In women, it prompts follicles in the ovaries to grow and produce estradiol. As estradiol and another ovarian hormone, inhibin, rise, they signal the pituitary to ease off. In men, FSH supports sperm production, and the testes signal back in a similar way.
When the ovaries or testes stop responding well, that brake weakens and the pituitary releases more FSH. That's why a high FSH usually points to a problem or change in the ovaries or testes, while a low FSH points toward the pituitary or the hypothalamus above it.
FSH and the menopause transition
As ovarian reserve dwindles, FSH climbs. After menopause it stays high. But during perimenopause FSH can jump up one month and drop back the next, because the ovaries still work intermittently. A single normal FSH doesn't mean you aren't in perimenopause, and a single high one doesn't confirm it.
For women over 45 with typical symptoms and changing periods, guidelines generally don't require an FSH test. Menopause is defined as 12 months without a period. FSH is more useful when symptoms start before 40 to 45, after a hysterectomy that kept the ovaries, or when periods have stopped for an unclear reason. The Menopause Society notes that FSH is the one hormone test that can be appropriate for helping to determine whether you're in menopause.
Why else FSH is tested
Clinicians may order FSH to:
- Evaluate infertility in women or men, or a low sperm count.
- Investigate irregular or absent periods.
- Help sort out the cause of low testosterone in men; high FSH and LH suggest a testicular problem, while low or normal values suggest a pituitary or hypothalamic cause.
- Look into early or delayed puberty.
Things that affect results
Hormonal birth control and menopausal hormone therapy suppress FSH, so results taken while you're on them may not reflect your natural state. In women who still cycle, FSH varies by cycle day and is often measured early in the cycle. Very low body weight, rapid weight loss and intense exercise can lower FSH. Testosterone therapy suppresses FSH in men, which is one reason it reduces sperm production.
FSH at HealifyMD
FSH may be part of the lab work your clinician orders before hormone therapy, alongside estradiol, LH and other markers. It's used to add context, not as a pass-fail test for treatment.
FSH: common questions
Can an FSH test tell me if I'm in perimenopause?
Not reliably on its own, because FSH swings during perimenopause. Your age, symptoms and cycle pattern usually tell more.
What FSH level means menopause?
Labs report their own ranges, and FSH is consistently high after menopause. But menopause itself is defined by 12 months without a period, not by a number.
Does birth control affect FSH?
Yes. Hormonal contraception suppresses FSH, so a test taken while you're on it doesn't reflect your natural levels.
Why would a man have FSH tested?
To evaluate infertility or low sperm count, or to help find the cause of low testosterone.
Does testosterone therapy change FSH?
Yes. External testosterone suppresses FSH and LH, which can lower sperm production.
What does low FSH mean?
It can point to a problem in the pituitary or hypothalamus, and in women may be linked to very low body weight or intense exercise.
Sources
We cite government agencies, professional societies and peer-reviewed research. See our editorial policy.
- Follicle-Stimulating Hormone (FSH) Levels TestMedlinePlus (U.S. National Library of Medicine)
- PerimenopauseThe Menopause Society
- What is hormone testing?The Menopause Society
- MenopauseMedlinePlus (U.S. National Library of Medicine)
- Evaluation and Management of Testosterone Deficiency guidelineAmerican Urological Association