Follicle-stimulating hormone (FSH)
Also known as: FSH, follitropin
A glycoprotein gonadotropin that drives ovarian follicle growth and estradiol production in women and supports spermatogenesis via Sertoli cells in men.
Overview
FSH shares the common α-subunit with LH, TSH and hCG. It acts on the FSH receptor, a Gs-coupled GPCR expressed only on granulosa cells in the ovary and Sertoli cells in the testis.
In the ovary, rising FSH at the end of each luteal phase rescues a cohort of antral follicles from atresia, stimulates granulosa proliferation and induces aromatase (CYP19), which converts theca-derived androgens to estradiol (the two-cell, two-gonadotropin model). FSH also induces LH receptors on granulosa cells of the dominant follicle, preparing it for ovulation, and stimulates inhibin B. The follicle most sensitive to FSH becomes dominant and survives the later fall in FSH, while the others undergo atresia.
In the testis, FSH stimulates Sertoli cells to produce androgen-binding protein, inhibin B, nutrients and growth factors for germ cells; with high intratesticular testosterone it initiates and maintains quantitatively normal spermatogenesis.
- Location
Source: gonadotrophs of the anterior pituitary. Targets: granulosa cells (ovary), Sertoli cells (testis).
Function
- Recruits and grows ovarian follicles; induces aromatase (estradiol synthesis) and LH receptors.
- Stimulates Sertoli-cell function and spermatogenesis.
- Stimulates inhibin secretion (which feeds back to suppress FSH).
- Physiology
Class: glycoprotein (α + β). Receptor: FSHR — Gs/cAMP. Half-life ≈3–4 h (longer than LH because of greater sialylation).
- Regulation
Stimulated by slow-frequency GnRH pulses and activin; inhibited by inhibin B (selective), estradiol and testosterone. FSH rises when gonadal inhibin falls — the earliest marker of declining ovarian reserve.
Clinical significance
Raised FSH — primary gonadal failure
Menopause and premature ovarian insufficiency (FSH typically >25–30 IU/L), Turner syndrome, Klinefelter syndrome, chemotherapy or radiation damage, testicular failure with azoospermia.
Therapeutic FSH
Recombinant or urinary FSH stimulates multifollicular development in IVF; excessive response risks ovarian hyperstimulation syndrome.
Compiled from standard anatomy and physiology references — see the Endocrine System sources. For education only; not medical advice.