FSH

FSH (follicle-stimulating hormone) is a pituitary hormone that stimulates egg maturation in the ovaries in women and sperm production in the testicles in men. Testing is used to investigate irregular cycles and infertility, suspected early menopause and ovarian, testicular or pituitary dysfunction.

Who the test is for

• women with irregular or absent periods;
• women and men undergoing infertility investigation; in men, a doctor usually also requests a semen analysis alongside hormones (more in the article on causes of male infertility);
• women with menopausal symptoms before age 45 and women under 40 with suspected premature ovarian insufficiency;
• people with suspected pituitary dysfunction;
• children with early or delayed puberty, on medical advice.

What FSH is and what it indicates

FSH is released by the anterior pituitary under hypothalamic control. In women, it stimulates ovarian follicle growth and oestrogen production in the first half of the cycle and, together with LH , controls ovulation. In men, it stimulates sperm production.

FSH depends on feedback: when the ovaries or testicles function less effectively, the pituitary releases more FSH. High FSH therefore suggests reduced ovarian or testicular function, while low FSH suggests a pituitary or hypothalamic disorder.

FSH, menopause and ovarian reserve

In menopause, the ovaries stop producing oestrogen, causing FSH to remain elevated. However, menopause in healthy women over 45 with typical symptoms and cycle changes is identified clinically without blood tests. FSH is a useful supplementary finding in women aged 40 to 45 with symptoms and cycle changes, and those under 40 with suspected premature ovarian insufficiency; a doctor may repeat measurement after several weeks.

In perimenopause, FSH varies greatly between cycles, so one normal result does not exclude the start of the transition. It is not measured to assess menopause in women using combined hormonal contraception or high-dose progestogens. Tests for individual stages are described on the menopause panelspage.

To assess ovarian reserve, or the number of remaining eggs, preference is now given to AMH (anti-Müllerian hormone) and an ultrasound antral follicle count because AMH varies less through the cycle. Nevertheless, high FSH at the beginning of a cycle suggests reduced ovarian reserve.

Save with a panel

Test FSH is also included in these panels.

Postmenopause assessment panelFSH, oestradiol, LHPrice of individual tests: 54.00€49.00€Details ›Perimenopause assessment panelFSH, LH, oestradiol, progesterone, TSHPrice of individual tests: 82.00€74.00€Details ›Early menopause assessment panelFSH, LH, oestradiol, progesterone, prolactin, TSHPrice of individual tests: 100.00€90.00€Details ›

All panels including FSH (15) ›

Preparation and sample

Blood is taken from a vein and fasting is not required. Women with regular cycles have blood taken early in the cycle, from day 2 to 5, most often day 2 or 3 (the first day of menstruation is day 1), or as advised by a doctor. With absent periods, after menopause and in men, blood can be taken on any day.

It is helpful to measure estradiolon the same day because elevated estradiol early in the cycle can lower FSH and conceal reduced ovarian reserve. Hormonal contraception and hormone therapy alter FSH, so tell your doctor if you use them. If you take biotin (e.g. hair and nail supplements), mention it at sampling.

How results are interpreted

FSH is expressed in IU/L. The reference range depends on sex, age, cycle phase and method and is printed on the report. A doctor interprets it alongside LH, estradiol, cycle pattern and symptoms.

• High FSH occurs in women during perimenopause and menopause and with reduced ovarian reserve or premature ovarian insufficiency. In men, it suggests testicular damage and reduced sperm production.
• Low FSH may suggest impaired pituitary or hypothalamic function (hypogonadotropic hypogonadism). Significant weight loss, exhausting exercise, elevated prolactin, pregnancy and hormonal contraception can also lower it.
• In polycystic ovary syndrome , FSH is usually normal or low-normal, while LH may be relatively elevated.

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed on the Contact page). Prices for all tests and panels are available in the service price list. In fertility investigation, FSH is most often measured in the Fertility Assessment Panel, which also includes LH, estradiol, prolactin, testosterone, TSH and AMH.

Frequently asked questions

On which cycle day is FSH measured?

With regular cycles, from day 2 to 5, most often day 2 or 3, counting the first day of menstruation as day 1. If periods are absent, blood can be taken on any day and a doctor interprets the result alongside estradiol.

What does high FSH mean?

In women, high FSH most often means reduced ovarian function, which is expected in perimenopause and menopause. In younger women it may suggest reduced ovarian reserve or premature ovarian insufficiency, and in men reduced sperm production. One result is insufficient for a conclusion, so a doctor often repeats measurement or adds other tests.

Can you become pregnant with high FSH?

High FSH suggests reduced ovarian reserve and a weaker response to stimulation in assisted reproduction, but does not mean pregnancy is impossible. A gynaecologist assesses the outlook alongside age, AMH and ultrasound findings.

Why is FSH measured in men?

In men, FSH helps investigate infertility and low testosterone. Alongside LH, testosterone and a separately referred semen analysis, it indicates whether the problem originates in the testicles or pituitary.