Knowledge Centre
Hormones & blood testsDraft: awaiting clinical review
Follicle-stimulating hormone (FSH)
A pituitary hormone that stimulates follicles to grow. It is usually measured early in the cycle.
Overview
FSH is released by the pituitary gland and drives follicle development. It is usually measured on days 2–5 of the cycle.
As ovarian reserve declines, the pituitary produces more FSH.
What is well established
- A raised early-cycle FSH can suggest reduced ovarian reserve, but levels vary from cycle to cycle.
- AMH and antral follicle count are generally more reliable markers of ovarian reserve than FSH alone.
- In women over 45 with typical symptoms, an FSH test is not needed to diagnose perimenopause or menopause.
Uncertain or emerging evidence
- A single FSH result has limited value in predicting natural fertility.
This guide is general information and does not replace advice about your own circumstances. Clinical review pending.