Blood Test: Luteinizing Hormone (LH)

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What Is a Blood Test?

By taking and testing a small sample of a person’s blood, doctors can check for many kinds of diseases and conditions. Blood tests help doctors check how the body’s organs are working and see if medical treatments are helpful.

To help your child get ready for a blood test, find out if they need to fast (not eat or drink) or should stop taking medicines before the test. Explain what to expect during the test. If your child is anxious about it, work together on ways to stay calm.

What Is Luteinizing Hormone?

Luteinizing hormone (LH) is a hormone made by the pituitary gland. It plays an important role in sexual development.

In kids, luteinizing (LOO-tee-uh-nye-zing) hormone levels are high right after birth. Then they fall and stay low until puberty nears (usually between ages 10 and 14). The brain makes gonadotropin-releasing hormone (GnRH), which starts the changes toward sexual maturity. GnRH signals the pituitary gland to release two puberty hormones into the bloodstream: LH and follicle stimulating hormone (FSH).

LH ad FSH tell the testes and ovaries to make hormones that bring about changes during puberty. Human sex hormones work closely with one another. So doctors might do an LH test along with blood tests that measure FSH, estradiol, and testosterone. Together, the results can give doctors a more complete picture of a child or teen's sexual maturation status.

Why Are LH Tests Done?

An LH test measures the level of this hormone in the bloodstream. Doctors may order an LH test if puberty starts earlier or later than expected.

The test also can check for damage or disease of the testes or ovaries, pituitary gland, or hypothalamus, an area of the brain that links the nervous system with the hormone-making endocrine system.

In adults and teens, LH levels can also help doctors evaluate fertility issues and menstrual problems.