Prolactin (hPRL, LTH) is secreted by the acidophil cells of the adenohypophysis. It is unique among hormones in that it responds to inhibition via the hypothalamus rather than to stimulation; that is, prolactin is secreted except when influenced by the hypothalamic inhibiting factor, which is believed to be the neurotransmitter dopamine.

The only known function of hPRL is to induce milk production in a female breast already stimulated by high estrogen levels. Once milk production is established, lactation can continue without elevated prolactin levels. Levels of hPRL rise late in pregnancy, peak with the initiation of lactation, and surge each time a woman breast-feeds. The function of hPRL in men is not known.

Excessive circulating hPRL disturbs sexual function in both men and women. Women experience amenorrhea and anovulation, and they may have inappropriate milk secretion (galactorrhea). Men experience impotence, which occurs even when testosterone levels are normal, and sometimes gynecomastia.⁴¹

• Therapy with drugs such as estrogens, oral contraceptives, reserpine, -methyldopa, phenothiazines, haloperidol, tricyclic antidepressants, and procainamide derivatives may produce elevated levels.
• Episodic elevations may occur in response to sleep, stress, exercise, and hypoglycemia.
• Therapy with dopamine, apomorphine, and ergot alkaloids may produce decreased levels.

• Sexual dysfunction of unknown etiology in men and women, because excessive circulating hPRL may indicate the source of the problem (e.g., damage to the hypothalamus, pituitary adenoma)
• Failure of lactation in the postpartum period or suspected postpartum hypophyseal infarction (Sheehan's syndrome), or both, as indicated by decreased levels
• Suspected tumor involving the lungs or kidneys, with elevated levels indicating ectopic hPRL production
• Support for diagnosing primary hypothyroidism as indicated by elevated levels

Nursing Care Before the Procedure

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

• Because many drugs may alter serum hPRL levels, a medication history should be obtained. It is recommended that drugs that may alter test results be withheld for 12 to 24 hours before the test, although this practice should be confirmed with the person ordering the study.

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.
• Complications and precautions: Assess for signs and symptoms of pituitary conditions such as mood changes; body image changes; sexual dysfunction in men; and menstrual, milk secretion, and weight gain abnormalities in women.