Inhibin B

Women: 20 to 200 ng/L · Men: 25 to 325 ng/L

Ranges depend heavily on the assay, on the day of the cycle in women (highest in the first half, very low after the menopause) and on age, so the lab's printed range is the one to use.

Inhibin B is a hormone made by the ovaries in women and by the sperm-producing cells of the testes in men. It feeds back to the pituitary to hold FSH in check. In men its level reflects how active sperm production is; in women it is another marker of the follicles remaining in the ovary.

It is a specialist test, requested mainly in male fertility clinics as a marker of sperm production, in the assessment of ovarian reserve alongside AMH, in children with puberty problems, and to follow a rare ovarian tumour called a granulosa cell tumour.

• Granulosa cell tumours of the ovary, where it is used as a follow-up marker
• The first half of the menstrual cycle, in women
• Fertility treatment that stimulates the ovaries
• Polycystic ovary syndrome, slightly, in some women

• Older age and the menopause, in women
• Reduced sperm production in men, from any cause
• Chemotherapy, radiotherapy or surgery affecting the ovaries or testes
• The second half of the menstrual cycle
• Hormonal contraception
• Anabolic steroid or testosterone use in men

• In women the value depends on the day of the cycle
• Different assays give different numbers, so results from two labs are not comparable
• Hormonal contraception lowers it while it is being taken

In women it is usually taken on day 2 to 5 of the cycle; in men a morning sample is preferred. It is sent to a specialist laboratory.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.