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What is a Luteinizing Hormone (LH) test? 

An LH test, also called interstitial cell-stimulating hormone test, is used to determine the levels of LH in blood. LH is a reproductive hormone produced by pituitary gland, a pea-sized gland in brain. It plays a vital role in sexual development, especially the development of ovarian follicles in females and Leydig cells in male.

LH levels are high in infants at birth but it gradually reduces until puberty (usually 10-14 years of age). Once puberty approaches, LH along with follicle-stimulating hormone (FSH) aids in the production of testosterone in boys and oestrogen in girls.

In women, LH is released from the brain and stimulates ovaries to release a matured egg during the ovulation phase of the menstrual cycle. In men, testosterone production due to LH is responsible for sperm production. Since LH is associated with ovulation in women and sperm production in men, an LH test can help identify fertility problems. Also, this test can help detect a disorder of the pituitary gland.

  1. Why is an LH test performed?
  2. How do you prepare for an LH test?
  3. How is an LH test performed?
  4. What do LH test results indicate?

An LH test is performed to identify problems associated with fertility. It is done in the following cases:  

No special preparations are needed for this test. However, your doctor will ask you to temporarily stop some medicines, such as birth control pills and testosterone, as it may interfere with test results. Also, it is important to inform the doctor about all the medicines, including vitamins, herb and supplements, which you are taking.

In case of women of childbearing age, LH test is done on a specific day of the menstrual cycle. Inform the doctor about any previous exposure to the radioisotope in tests, such as nuclear medicine.

Wearing a small sleeve t-shirt or shirt can help in the easy withdrawal of blood from arm.

A blood sample is collected from a vein in the arm using a needle. Moderate pain is felt when the needle is inserted into the vein. Some people feel only a stinging or prick. A slight bruise or throbbing may be observed at the site of injection, which disappears quickly. The site of injection may be sore for a while.

Some of the risks associated with this test include a light-headed feeling, excessive bleeding, accumulation of blood or infection at the site of injection.

Variations in test results may be seen based on the age, sex, medical history, method of testing and other factors. 

Normal results: The normal ranges are given below:

Different populations

Normal levels (International units per litre)

Girls (1-10 years of age)

0.03-3.9

Women (follicular phase of the menstrual cycle)

1.68-15

Women (mid-cycle peak)

21.9-56.5

Women (luteal phase)

0.61-16.3

Women (postmenopausal)

14.2-52.3

Men

1.24-7.8

Abnormal results:

In women, abnormally high LH levels during the non-ovulatory phase of the menstrual cycle indicate menopause or polycystic ovary syndrome. Low LH levels in women indicate anorexia, malnutrition or stress. A pituitary gland disorder can cause both low and high LH levels. 

In men, high LH levels with low testosterone levels may indicate that the testicles are not responsive to the signals given by LH for producing testosterone. Abnormally low levels of LH in men indicates that the pituitary gland is unable to produce sufficient LH, and hence low levels of testosterone are also be observed.

Higher than normal levels of LH in women can be due to the following:

  • Absence of ovulation in women of childbearing age
  • During or after menopause
  • A rare genetic condition called Turner’s syndrome 
  • Imbalance in sex hormones in conditions such as polycystic ovary syndrome
  • Little or no production of hormones by the ovaries (Read more: Female hormones imbalance)

Higher than normal levels of LH in men can be due to the following:

  • Absence of testes or non-functional testes
  • Overactive endocrine glands or tumour-producing endocrine glands
  • Genetic conditions, such as Klinefelter’s syndrome

Abnormally lower LH levels are usually due to reduced production by the pituitary gland.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational perspective and is in no way a substitute for medical advice from a qualified doctor. 

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References

  1. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Luteinizing Hormone (Blood)
  2. Chernecky CC, Berger BJ. Luteinizing hormone - blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders. 2013 pp 743-744.
  3. Jeelani R, Bluth MH. Reproductive function and pregnancy. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017 Chapter 25.
  4. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Luteinizing hormone (LH) blood test
  5. Department of Molecular and Cell Biology [internet]: University of California. Berkley (U.S.); FSH and LH
  6. Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 649-651.