What is inhibin?
Inhibin is a hormone made by the granulosa cells of ovarian follicles (and by the placenta in pregnancy) that tells the pituitary gland to release less follicle-stimulating hormone (FSH). Inhibin B rises in the follicular phase from growing follicles; inhibin A peaks in the luteal phase from the corpus luteum. Falling inhibin with age helps explain rising FSH in perimenopause.
Inhibin A and inhibin B
| Form | Main source | When it is highest |
|---|---|---|
| Inhibin B | small growing follicles | early to mid follicular phase |
| Inhibin A | the dominant follicle, then the corpus luteum | luteal phase; also in pregnancy |
How it fits the hormone loop
The brain releases FSH to grow follicles. As follicles grow, they release inhibin and estrogen, which tell the brain to ease off. This feedback helps make sure usually only one follicle reaches ovulation. When few follicles remain, inhibin B drops, FSH rises and cycles often get shorter: one of the first hormonal signs of perimenopause.
Where you might meet inhibin in tests
- Pregnancy screening: inhibin A is part of the second-trimester "quad test" for chromosomal conditions.
- Fertility: inhibin B was once used to estimate ovarian reserve; AMH has largely replaced it because it is more stable.
- Rare ovarian tumors: granulosa cell tumors can produce high inhibin, which is used to monitor them.
Inhibin itself does not directly cause mood symptoms, but the hormone shifts it signals, like the earlier, less predictable cycles of perimenopause, often come with sleep and mood changes. See anti-Müllerian hormone.
Frequently asked questions
Can I get my inhibin tested?
It is rarely tested on its own. For fertility, doctors usually check AMH, FSH and an ultrasound follicle count instead.
Does low inhibin mean I can't get pregnant?
No single hormone predicts fertility. Low inhibin B suggests fewer follicles, but egg quality and age matter more.
Sources
- Welt CK et al. Female reproductive aging is marked by decreased secretion of dimeric inhibin. J Clin Endocrinol Metab (1999)
- MedlinePlus: Quadruple screen test
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
Follicle-stimulating hormone (FSH): definitionFSH is the pituitary hormone that makes ovarian follicles grow. What it does in your cycle, what high or low FSH means, and how it changes near menopause.What is anti-Müllerian hormone (AMH)?AMH is a hormone made by small ovarian follicles. What an AMH level tells you about ovarian reserve, what it can't tell you, and when doctors test it.
Ovarian reserve: definition and meaningOvarian reserve is the number of eggs left in your ovaries. How AMH and follicle counts estimate it, what it can and can't predict, and how age affects it.
Menstrual cycle hormones: a simple chart of what rises and fallsMenstrual cycle hormones explained simply: how estrogen, progesterone, LH and FSH rise and fall through each phase, and how they shape mood and energy.
Perimenopause: definition and meaningPerimenopause is the transition before menopause when hormones fluctuate and periods change, usually starting in your 40s. Signs, mood changes and timing.