Summary

• Luteinising hormone (LH) is one of the hormones that brings about sexual development in children. In adults, it regulates the menstrual cycle in females and triggers the making of sperm in males.
• Measuring the level of LH in a sample of blood can help diagnose fertility and pituitary disorders.
• In children, it is used to investigate early or delayed puberty.
• The LH test is typically requested together with other hormone tests such as follicle stimulating hormone (FSH), oestradiol, progesterone and testosterone.

What is luteinising hormone (LH)?

Luteinising hormone (LH) is made in the pituitary gland and plays an important role in sexual development in children and fertility in adults.

In females:

• LH helps control the menstrual cycle. It works together with follicle stimulating hormone (FSH) to trigger the egg follicles to produce oestradiol.
• At about mid-cycle there is a surge of FSH and LH and this is followed by ovulation - the release of the egg from the ovaries.
• During the second half of the menstrual cycle FSH stimulates the production of progesterone.
• FSH also enables the ovary to respond to LH. As a woman ages and menopause approaches, ovarian function wanes and eventually stops. As this occurs, FSH and LH levels rise.

In males:

• LH causes the testicles to make sperm. Normally, LH levels in males do not change very much throughout the course of their life. In males, LH is measured to investigate the cause of low testosterone.

In children, LH and FSH levels rise soon after birth and then fall to very low levels in infancy. They remain low until puberty, when levels begin to rise again.

How is LH made?

LH is part of a complex feedback system of glands, hormones and sex organs that together regulate sexual development and function. As well as LH, this involves FSH, and the reproductive hormones, testosterone, oestradiol and progesterone.

Hormones are chemical messengers that are made by your glands and travel in your bloodstream to control the actions of specific cells in your tissues or organs. When they reach their target, they attach to a cell’s receptors, stimulating a response.

• The hypothalamus in the brain makes gonadotropin-releasing hormone (GnRH), which signals the pituitary gland to release LH and FSH into the bloodstream.
• LH and FSH trigger the ovaries (in females) or testicles (in males) to make the reproductive hormones oestradiol and progesterone (in females) and testosterone (in males).
• The amount of reproductive hormones made by the ovaries or testicles let your hypothalamus and pituitary gland know when to step up or slow the production of LH and FSH.

If any of the glands or organs in this system are not working as they should, abnormal levels of hormones are made.

Why get tested?

LH testing is often used together with other tests including FSH, oestradiol, progesterone and testosterone. Abnormal levels of LH may be a sign of a problem in:

• the pituitary gland
• the hypothalamus
• reproductive glands – your ovaries or testicles

These tests are used to investigate:

• infertility
• low sperm count
• irregular periods
• pituitary gland disorders
• menopause
• delayed or early puberty

LH, FSH and ovarian hormones during the menstrual cycle

LH testing is used along with other hormone tests to investigate irregular menstrual periods or confirm menopause.

Day 0 is the first day of menstruation. FSH stimulates the growth of eggs in the ovaries during the first half of the menstrual cycle (follicular phase). It does this by causing the egg follicle to make oestradiol.

At about mid-cycle there is a surge of FSH and LH which is followed by ovulation - the release of the egg from the lead follicle at about day 14. The fertile period begins about five days before the LH surge and ends the following day – the egg quickly degenerates if not fertilised.

During the second half of the menstrual cycle (luteal phase) FSH stimulates the production of progesterone.

Menstrual cycle times can vary widely between people. This makes it difficult to calculate the exact timing of the fertile period. As a woman ages and menopause approaches, ovarian function wanes and eventually stops and as this occurs, the levels of both LH and FSH rise.

Males

LH causes the testicles to make sperm. Normally, LH levels in men do not change very much throughout the course of their life. In men, LH can be measured to investigate the cause of low testosterone.

Children

LH and FSH levels rise soon after birth and then fall to very low levels in infancy. They remain low until puberty, when levels begin to rise again. LH can be measured to investigate issues with puberty in children.

Having the test

Sample

Blood

Any preparation?

None

Your results

Reading your test report

Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.

Interpreting results

Results of an LH test are typically considered with results of other hormone tests, such as FSH, oestrogens, progesterone and testosterone.

Females

• As part of an infertility investigation, a high or low LH is not diagnostic but helps build a picture of what may be the cause. For example, a hormone imbalance may affect a woman’s menstrual cycle and/or ovulation. Your medical team will consider all test and clinical information to establish a diagnosis.
• LH and FSH levels can help differentiate between whether there is a problem with the ovaries or whether there is a disorder of either the pituitary gland or the hypothalamus.
• Increased levels of LH and FSH are consistent with a problem with the ovaries.
• Low levels of LH and FSH suggest a pituitary or hypothalamic problem.
• When a woman enters the menopause, her ovaries stop working and LH and FSH levels rise but generally, LH rises less and later than FSH.

Males

• High LH levels are due to a problem with the testicles. This can be due to developmental issues or an injury to the testicles.
• Low levels of LH suggest pituitary or hypothalamic disorders.

Children

• Early puberty: higher levels of LH and FSH than expected for age along with the development of secondary sexual characteristics such as pubic hair and breasts at an unusually young age are an indication of early puberty. This is much more common in girls than in boys.
• Delayed puberty: LH and FSH levels can be normal or below what is expected for a person within their age range.

Reference intervals

Your results will be compared to reference intervals (sometimes called a normal range).

• Reference intervals are the range of results expected in healthy people.
• When compared against them your results may be flagged high or low if they sit outside this range.
• Many reference intervals vary between labs so only those that are standardised or harmonised across most laboratories are given on this website.

If your results are flagged as high or low this does not necessarily mean that anything is wrong. Your doctor needs to take your medical history to help interpret your result.

Any more to know?

• LH levels can be higher with the use of some medications including cimetidine, clomiphene and naloxone.
• LH levels can be lower with oral contraceptives, phenothiazines and hormone treatments.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

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