Luteinizing Hormone (LH) Blood Test

What Is Luteinizing Hormone?

Luteinizing (LOO-tee-uh-nye-zing) hormone, or LH, is a hormone made by the pituitary gland. It plays an important role in sexual development.

In kids, LH levels are high right after birth and peak at about 1 to 3 months. 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 and FSH tell the testes and ovaries to make hormones that bring about changes during puberty, like the development of sperm or eggs.

Why Are LH Tests Done?

An LH test measures the level of LH in the blood. 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 (hi-po-THAL-uh-mus), an area of the brain that links the nervous system with the hormone-making endocrine system.

In teens and adults, LH levels can also help doctors check menstrual problems and fertility issues (trouble having a baby).

Top Things to Know

• The luteinizing hormone (LH) blood test checks how much LH is in the blood.
• This test may be done to see why puberty is early or late, or for other reasons.
• Kids might need to stop taking certain medicines or not eat or drink before the blood test.
• Your doctor can explain what it means if the LH level is high or low.

How Can I Help My Child Prepare for a Blood Test?

If your child has started getting periods, the LH test might have to be done on a certain day of the menstrual cycle. Also, tell your doctor if your child has had a nuclear medicine imaging scan lately because radioactive material left from the scan could change LH test results.

To help kids 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 nervous about it, work together on ways to stay calm. Deep breathing or even imagining being in a peaceful place that makes your child feel safe and relaxed can help.

What Do LH Test Results Mean?

Your doctor will explain what the results of the LH test mean for your child. “Normal” levels vary based on things like age and sex.

High LH Levels

LH levels could be high because of precocious (early) puberty.

In females, high LH levels sometimes happen because of ovary problems (like polyendocrine metabolic ovarian syndrome), gene differences like Turner syndrome, or menopause (when periods stop completely). Too much or too little of female sex hormones may also raise LH levels.

In males, the LH level might be high because of problems with the testes or endocrine glands, or genetic differences (like Klinefelter syndrome).

Low LH Levels

In females and males, low LH levels may be due to a problem with the pituitary gland or hypothalamus.

What Else Should I Know?

Sex hormones work closely with each other. So doctors might do an LH test along with other blood tests that measure hormones like:

• FSH
• estradiol
• testosterone

Together, the results can give a more complete picture of sexual development.

If you have questions about the LH test or what the results mean, talk with your doctor.