Luteinizing hormone is secreted by the basophil cells of the adenohypophysis in response to stimulation by GnRH, the same hypothalamic releasing factor that stimulates FSH release. LH affects gonadal function in both men and women. In women, a surge of LH occurs at the midpoint of the menstrual cycle and is believed to be induced by high estrogen levels. LH causes the ovum to be expelled from the ovary and stimulates development of the corpus luteum and production of progesterone. As progesterone levels rise, LH production decreases. In men, LH stimulates the interstitial Leydig cells, located in the testes, to produce testosterone.

During childhood, LH levels decrease and are lower than those of FSH. Similarly, LH levels rise after those of FSH as puberty approaches. During the childbearing years, LH levels in women vary according to the menstrual cycle but remain fairly constant in men. Decreased LH levels after puberty are associated with male and female infertility. After the reproductive years, as gonadal hormones decline, LH levels rise in response to normal feedback mechanisms. The rise in LH levels, however, is not as marked as that for FSH levels. A 24-hour urine specimen also can be collected and tested for LH.

Note: Results should be evaluated in relation to other tests of gonadal function.

• In menstruating women, values vary in relation to the phase of the menstrual cycle.
• Values are higher in postmenopausal women.
• Drugs containing estrogen tend to cause elevated LH levels.
• Drugs containing progesterone and testosterone may lead to decreased levels.

• Evaluation of male and female infertility, as indicated by decreased levels
• Support for diagnosing infertility caused by anovulation as evidenced by lack of the midcycle LH surge
• Evaluation of response to therapy to induce ovulation
• Suspected pituitary or hypothalamic dysfunction:
  • Elevated levels may be seen in pituitary tumors.
  • Decreased levels are associated with hypothalamic lesions and panhypopituitarism.

Nursing Care Before the Procedure

Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

• It is recommended that any drugs known to alter LH levels be withheld for 12 to 24 hours before the test, although this practice should be confirmed with the person ordering the study.
• In women, the phase of the menstrual cycle should be ascertained, if possible.
• If the test is being performed to detect ovulation, the client should be informed that it may be necessary to obtain a series of samples over a period of several days to detect peak LH levels.

A venipuncture is performed and the sample collected in a red-topped tube. The sample should be handled gently to avoid hemolysis and transported promptly to the laboratory.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.

• Resume any medications withheld before the test.
• Abnormal test results, complications, and precautions: Respond as for FSH testing, because LH is usually performed on the same blood sample.