Luteinizing hormone (LH) is a hormone produced by cells in the anterior pituitary gland. Luteinizing hormone plays a crucial role in sexual development is also responsible for regulating key reproductive functions, such as controlling the menstrual cycle and triggering the release of an egg from the ovary. For people with sperm, LH regulates testosterone production.

What is luteinizing hormone (LH)?

Luteinizing hormone (LH), also called interstitial cell stimulating hormone or lutropin, is important for sexual development and reproduction. Luteinizing hormone is produced by the pituitary gland, located below your brain.

Luteinizing hormone and female fertility

LH is important for female fertility, and affects the length of the menstrual cycle, estrogen and progesterone production, and readying the uterus for a fertilized egg. A surge of LH during the menstrual cycle is what prompts the ovaries to release an egg. Therefore, identifying when LH levels are elevated can indicate ovulation, the most effective time to try to conceive. This can be done at home using a urine ovulation prediction kit.

Balance is important. Research indicates that excessively high LH levels may be linked to higher rates of miscarriage and infertility. Elevated LH levels may also indicate polycystic ovary syndrome, which can result in infertility. Insufficient LH may be caused by problems with the pituitary gland, and can affect fertility as well. This may be treated with estrogen replacement therapy.

Luteinizing hormone and male fertility

LH prompts the Leydig cells in the testicles to release testosterone, which is essential for sperm production and fertility. Unusually high levels of LH combined with low testosterone may indicate damage to the testicles, such as from chemotherapy. Elevated LH levels can also suggest that you have the genetic disorder Klinefelter’s syndrome, which can lead to infertility.

Testing for luteinizing hormone

Testing for the level of LH in your blood can help diagnose fertility issues. The test may be performed when:

• a couple isn’t able to become pregnant after 12 months
• people are looking for the cause of low sperm count or low sex drive
• individuals are no longer getting their menstrual period, or getting it irregularly
• people display symptoms of a pituitary disorder
• children appear to reach puberty at an unusually young or old age

In pre-menopausal adults with ovaries, a normal LH test result is 5–25 IU/L. In adults with testes, the standard result is approximately 1.8–8.6 IU/L.