LH

A urine test may be used to detect the surge in LH that indicates that ovulation will occur in the next 1-2 days.

In children, FSH and LH are used to diagnose delayed and precocious (early) puberty.

LH is sometimes measured in relation to gonadotropin releasing hormone (GnRH) to distinguish between primary or secondary disorder of the hypothalamic-pituitary axis. GnRH is the hormone produced by the hypothalamus that stimulates the pituitary to release LH and FSH. For this test, a baseline blood sample is drawn and then the patient is given an injection of GnRH. Subsequent blood samples are drawn at specified times, and the level of LH is measured. This test can help differentiate between disease of the ovaries or testes (primary) and a disorder of the pituitary or hypothalamus (secondary). It is also often helpful in the evaluation of precocious or delayed puberty.

If any or some of these signs appear at a younger than average age or are delayed beyond the expected age range for puberty, it may be an indication of a more serious problem involving the hypothalamus, pituitary, gonads (ovaries or testes), or other systems. The measurement of LH and FSH may differentiate between benign symptoms and true disease. Once it is established that symptoms are a result of true disease, further testing can be done to discern the underlying cause.

• Ovarian agenesis (failure to develop ovaries) 
• Chromosomal abnormality, such as Turner’s syndrome
• Ovarian steroidogenesis defect such as 17 alpha hydroxylase deficiency

Premature ovarian failure due to:

• Radiation 
• Chemotherapy 
• Autoimmune disease

Chronic anovulation (failure to ovulate) due to: 

• Polycystic ovary syndrome (PCOS)
• Adrenal disease 
• Thyroid disease 
• Ovarian tumor

When a woman enters menopause and her ovaries stop working, LH levels will rise.

Low levels of LH and FSH are seen in secondary ovarian failure and indicate a problem with the pituitary or hypothalamus.

In men, high LH levels indicate primary testicular failure. This can be due to developmental defects in testicular growth or to testicular injury, as described below.

Developmental defects: 

• Gonadal agenesis 
• Chromosomal abnormality, such as Klinefelters syndrome

Testicular failure: 

• Viral infection (mumps) 
• Trauma 
• Radiation 
• Chemotherapy 
• Autoimmune disease 
• Germ cell tumor

Low levels are consistent with pituitary or hypothalamic disorders.

The results for the test for LH response to GnRH can help differentiate between primary dysfunction (failure of the ovaries or testes) and secondary disorder (a problem involving the pituitary or hypothalamus). Once the baseline level of LH has been measured, a dose of GnRH is given by injection. A subsequent increase in the level of LH indicates that the pituitary responded to the GnRH and points to a disorder involving the ovaries or testes. A reduced level of LH shows that the pituitary did not respond to the GnRH and suggests a disease involving the pituitary or hypothalamus.

In young children, high levels of LH and FSH and/or development of secondary sexual characteristics at an unusually young age are an indication of precocious puberty. This is much more common in girls than in boys. This premature development can have many different underlying causes that need to be diagnosed and treated. Some of the causes include:

Normal prepubescent levels of LH and FSH in children exhibiting some signs of pubertal changes may indicate a benign form of precocious puberty with no underlying or discernable cause or may just be a normal variation of puberty.

In delayed puberty, LH and FSH levels can be normal or below what is expected for a youth within the age range of puberty. The test for LH response to GnRH may need to be performed along with other testing to diagnose the reason for the delayed puberty. Some of the causes for delayed puberty can include:

If you’ve recently had a nuclear medicine scan, the radioisotopes used in the scan may interfere with results of the LH test.