Hormones
LH
Pituitary hormone that triggers ovulation and, in men, drives testosterone production; assessed together with FSH.
Everything about this testWhat it measures
LH (luteinizing hormone) comes from the pituitary gland. In women it rises sharply for a short time halfway through the cycle, which triggers ovulation; after that it drives the production of progesterone. In men, LH prompts the testicles to make testosterone. Like FSH, LH rises when the sex glands work less well and falls when the control from the brain falters.
- The cause of low testosterone in men: a high LH points to the testicles, a low LH to the pituitary gland or to suppression by anabolic steroids
- Polycystic ovary syndrome (PCOS): LH is often raised relative to FSH
- Disturbed control when periods stop: underweight, stress, intensive sport, a pituitary condition
- Failure of the ovaries or testicles (together with FSH)
High
In women, a high value around ovulation is normal; outside those days, a raised LH fits PCOS, often with an irregular cycle, acne and excess hair growth, or reduced function of the ovaries, as in menopause. In men, a raised LH with a low testosterone indicates that the testicles themselves make less, for example after a mumps infection, chemotherapy, radiotherapy or in Klinefelter syndrome. A raised LH with a normal testosterone can be an early sign of reduced testicular function at an older age.
Low
A low LH is normal when using the pill, during pregnancy and breastfeeding, and before puberty. In men with a low testosterone, a low or low-normal LH points to a cause in the pituitary gland or hypothalamus, or to suppression by anabolic steroids, testosterone treatment or opioids; after stopping steroids, recovery can take months. In women whose periods have stopped, a low LH fits underweight, an eating disorder, intensive training, stress or a pituitary condition. A low value on its own, without symptoms and without the other hormones, says little.
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 LH together with FSH, estradiol or testosterone and the day of the cycle, and usually repeats an abnormal value after a few weeks. With suspected PCOS, an ultrasound often follows; with a pituitary cause or a condition of the testicles, a referral to a gynecologist, urologist or internist-endocrinologist.
Reliability
LH is virtually never assessed on its own, but together with FSH and estradiol or testosterone; it then helps to locate the cause of an abnormality. According to the Dutch Society for Clinical Chemistry (NVKC), LH is unsuitable for establishing menopause (FSH says more there), and during menopause the hormone values vary too much to establish menopause with a blood test. For the diagnosis of PCOS, a raised LH/FSH ratio is not a criterion: the diagnosis is based on the cycle, signs of too much male hormone and an ultrasound.
Limitations
- In women, the day of the cycle determines the result: the standard blood draw is on day 2 to 5; around ovulation LH is many times higher for a short time.
- The pill, hormone therapy, pregnancy and breastfeeding suppress LH.
- Anabolic steroids, testosterone, opioids and severe illness or malnutrition lower LH; biotin supplements can interfere with the measurement.
- LH is released in pulses, so two measurements on the same day can differ.
How common is this
PCOS occurs in about 5 to 10 in 100 women of childbearing age and is the most common cause of an irregular cycle. A testosterone deficiency due to the testicles or the pituitary gland is estimated to occur in a few percent of men over 40; suppression by anabolic steroids is a common, usually temporary cause of a low LH in strength athletes.
Who is this useful for
Useful together with FSH in men with a repeatedly low testosterone to locate the cause, after stopping anabolic steroids to monitor recovery, and in women with absent or irregular periods or suspected PCOS. Not useful for establishing menopause and not as a stand-alone test when trying to conceive. When using the pill, the result cannot be interpreted.
Downsides and risks
- Without the day of the cycle, a normal peak around ovulation can be read as 'too high'; a raised LH does not prove PCOS.
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