LH (Luteinizing Hormone): What It Is and What the Test Shows

A referral for an LH test often raises questions: the name of the hormone says little, and the numbers on the form even less. Luteinizing hormone is produced by the anterior pituitary gland, and it is involved in the functioning of the reproductive system in both women and men. Below is a calm breakdown of why this test is needed and how doctors read it.

What LH is and where it is produced

LH is a peptide hormone secreted by the gonadotropic cells of the anterior pituitary, a small gland at the base of the brain. Together with follicle-stimulating hormone (FSH), it is needed for the normal functioning of the reproductive system. LH production is regulated by the hypothalamus: it sends signals to the pituitary, and the sex hormones of the ovaries or testes, through a feedback mechanism, signal when to start and stop synthesis. LH is usually measured in a blood sample, and in some cases in urine.

What luteinizing hormone does in women

In women, LH helps control the menstrual cycle and triggers the release of an egg from the ovary — ovulation. LH levels rise rapidly just before ovulation, and this monthly surge signals when the chance of conception is highest. LH also stimulates the ovaries to produce estrogens and supports the corpus luteum for about 14 days. In childhood the level is low; before puberty it begins to rise slowly — usually between the ages of six and eight.

LH in men: the role of the hormone

In men, LH causes the testes to produce testosterone, which is needed for sperm production. Normally, LH levels in men change little. An LH test in men is ordered for infertility, low sperm count, decreased libido, loss of muscle mass and body hair, and also when a pituitary problem is suspected.

LH test: when it is ordered and how the result is interpreted

The test helps identify the causes of LH levels that are too high or too low. In women it is ordered for irregular or absent periods, difficulty conceiving, to check ovulation, and when menopause is suspected. In children and adolescents — to determine whether a condition is causing early or delayed puberty. LH is usually checked together with FSH, as well as with estrogens, testosterone, and progesterone. Reference values depend on the laboratory; the guidance from reference tables is given below.

Ranges may differ slightly between laboratories, so the specific result should be discussed with a doctor.

• In women, elevated LH occurs with anovulation, sex hormone imbalance, for example in polycystic ovary syndrome, during and after menopause.
• In men, high LH is possible with absent or impaired testicular function, and with genetic features.
• In children, a high level occurs with precocious puberty.
• Low LH may be associated with insufficient hormone production by the pituitary.

Why LH can be elevated or decreased

Persistently high LH indicates a disruption of the feedback between the gonads and the hypothalamus. This is normal in menopause, but during reproductive age it is considered an abnormality. Possible causes include premature menopause, ovarian hypofunction, Turner syndrome, and some forms of congenital adrenal hyperplasia. Decreased LH secretion can lead to hypogonadism: in men it usually manifests as a reduced sperm count, in women as absent menstruation. This occurs in hypopituitarism, hereditary syndromes, eating disorders, and hyperprolactinemia.

When to see a doctor

Reasons for consultation include irregular or absent periods, unsuccessful attempts to conceive for 12 months, and decreased libido. In children — signs of sexual development before age 8 in girls and age 9 in boys, or their absence after age 13 and 14, respectively. Preparation for the test is discussed with a doctor: some medications and supplements affect the result, and women may need a specific day of the cycle.

An LH change on its own is not a reason to call an ambulance; 103/112 — in a life-threatening condition.

This material is for reference and does not replace consultation with a doctor.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer