LH is made in the pituitary gland of the brain. LH is a sex hormone that affects how a person’s reproductive organs function. In females, LH affects the ovaries. In males, it affects the testes.

Reproductive health problems can affect a person’s LH levels.

LH is involved in the following bodily processes :

• Puberty : LH levels affect the onset of puberty. High LH levels may cause early puberty and low LH levels may delay puberty.

• Menstruation : LH works with another sex hormone called follicle-stimulating hormone (FSH) to control menstrual cycles.

• Ovulation : An increase in LH, called an LH surge, triggers the release of an egg from an ovary.

• Progesterone release : An increase in LH triggers ovulation. The cell structure that is left after ovulation releases progesterone. Progesterone is needed to maintain a pregnancy.

• Testosterone production : LH binds to Leydig cells in the testes and triggers testosterone production. Testosterone levels affect sex drive.

• Sperm production : Testosterone, which LH levels affect, is needed for sperm production.

Your doctor may order the LH blood test in coordination with other hormone measurements, such as testosterone, progesterone, FSH, and estradiol.

The normal range of LH varies between males, females, and children. LH test results are measured in international units per liter (IU/L).

The following information is a guide to what high, low, and normal LH levels mean. People should discuss their LH test results with a doctor.

Normal ranges in men

For males, the normal range is 1.24–7.8 IU/L.

If LH levels are below the normal range, it may indicate a pituitary gland problem. Their pituitary gland may not be making enough LH, which may lead to low testosterone.

If LH levels are too high, the testes may not be responding to LH properly. LH may not be triggering testosterone production in the way that it should.

Normal ranges in women

For females, the normal range depends on where they are in their menstrual cycle, as follows :

• follicular phase, or the beginning of the cycle: 1.68–15 IU/L

• mid-cycle peak, around the middle of the cycle: 21.9–56.6 IU/L

• luteal phase, which is the end of the cycle: 0.61–16.3 IU/L

For females who have gone through menopause, the normal range is 14.2–52.3 IU/L.

LH test results help a doctor determine whether a male or female has problems with their reproductive system. Doctors also use LH tests to diagnose pituitary gland problems and the early or late onset of puberty.