Hormones
FSH
A pituitary hormone that controls the ovaries and testicles; high when they fail, low when the control signal falters.
Everything about this testWhat it measures
FSH (follicle-stimulating hormone) is made in the pituitary gland. In women it makes an egg follicle mature in the first half of the cycle; in men it controls the production of sperm cells. If the ovaries or testicles work less well, the brake falls away and FSH rises; if the control signal from the brain falters, FSH is low. In women the value varies with the cycle; in men it is fairly stable.
- Failure of the ovaries: early menopause in women under 40 (high FSH with low estradiol)
- Reduced function of the testicles in men, for example after mumps inflammation of the testicles, chemotherapy or with Klinefelter syndrome
- Disturbed control by the pituitary gland or hypothalamus (low FSH): underweight, stress, heavy exercise, a pituitary condition, use of anabolic steroids
- Confirmation of menopause when in doubt, for example after a hysterectomy
High
In women, a raised FSH fits reduced function of the ovaries: natural menopause or, under the age of 40, early menopause. A brief peak around ovulation is normal. In the years before menopause the value fluctuates strongly, so one high value does not prove menopause and a normal value does not rule it out. In men, a raised FSH points to testicles that make fewer sperm cells, for example after mumps inflammation of the testicles, chemotherapy, radiotherapy or with a congenital abnormality.
Low
A low FSH is normal with use of the contraceptive pill, during pregnancy and breastfeeding, and in children before puberty. In women whose periods have stopped, a low or low-normal FSH fits a disturbed control signal from the brain, as with underweight, an eating disorder, heavy training, stress or a pituitary condition. In men with a low testosterone, a low FSH and LH point to a cause in the pituitary gland or to suppression by anabolic steroids or testosterone use. A low value without symptoms has little meaning.
Preparation
- Do you have a menstrual cycle? Then have your blood taken on day 2 to 5 of your cycle (day 1 is the first day of your period). Without a cycle, on the pill or after menopause the day does not matter.
- Do you take biotin (vitamin B8, often in hair and nail supplements)? Stop at least 2 days before the sample is taken, or 4 days for a high dose.
If your result is abnormal
The GP assesses FSH together with LH, estradiol or testosterone and the cycle day. When early menopause is suspected, the measurement is repeated after at least four weeks and a referral to a gynecologist follows; men with an abnormal value are usually referred to a urologist or internist-endocrinologist.
Reliability
FSH is mainly useful for determining, with an abnormal sex hormone, whether the cause lies in the sex glands or in the pituitary gland. According to the Dutch GP guideline (NHG) on menopause, FSH has no value for diagnosing or predicting menopause, because the value varies strongly in those years. With an unfulfilled wish to have children, a single FSH value adds little to the initial testing (NHG guideline on subfertility). With absent periods under the age of 40, FSH does help to detect early menopause (NHG guideline on amenorrhea).
Limitations
- In women the cycle day determines the result: the standard is a blood draw on day 2 to 5 of the cycle; around ovulation FSH is temporarily raised.
- The contraceptive pill, hormone therapy, pregnancy and breastfeeding suppress FSH and make the result unusable.
- In the menopausal transition years FSH varies from month to month; one measurement says little.
- Anabolic steroids, testosterone and some medicines (including opioids) lower FSH; biotin supplements can disturb the measurement.
How common is this
Early menopause (before age 40) occurs in about 1 in 100 women. About 10 to 15 in 100 couples do not manage to get pregnant within a year; in some of them a hormonal cause plays a role. In men with reduced sperm quality, a raised FSH is a common finding.
Who is this useful for
Useful with absent or very irregular periods, especially under the age of 40, in men with a repeatedly low testosterone or reduced sperm quality to locate the cause, and after stopping anabolic steroids to follow the recovery of the hormone control. Not useful to determine whether someone is 'in menopause', and not as a standalone test when you want to have children: the result then says little, and testing for a cause first looks at the cycle, a past chlamydia infection and the semen. With use of the contraceptive pill, the result cannot be interpreted.
Downsides and risks
- A high FSH in the menopausal transition years can wrongly be read as 'proof' of menopause or of infertility, while the value may be normal a month later.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results