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Introduction ⬇

PRL is a pituitary hormone essential for initiating and maintaining lactation. The gender difference in PRL does not occur until puberty, when increased estrogen production results in higher PRL levels in females. Circadian changes in PRL concentration in adults are marked by episodic fluctuation and a sleep-induced peak in the early morning hours.

This test may be helpful in the diagnosis, management, and follow-up of a PRL-secreting tumor accompanied by secondary amenorrhea or galactorrhea, hyperprolactinemia, and infertility. It is also useful in the management of hypothalamic disease and in monitoring the effectiveness of surgery, chemotherapy, and radiation treatment of PRL-secreting tumors.

Normal Findings ⬆ ⬇

Nonpregnant women: 4–23 ng/mL or 4–23 μg/L

Pregnant women: 34–386 ng/mL or 34–386 μg/L by third trimester

Men: 3–15 ng/mL or 3–15 μg/L

Children: 3.2–20 ng/mL or 3.2–20 μg/L

Procedure ⬆ ⬇

  1. Ensure that the patient fasts for 12 hours before testing. Obtain a 5-mL venous blood sample (red-topped tube). Serum is used.

  2. Procure specimens in the morning, between 8:00 (0800 hours) and 10:00 a.m. (1000 hours). Draw in chilled tubes and keep specimens on ice.

  3. Observe standard precautions. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.

Clinical Implications ⬆ ⬇

  1. Increased PRL values are associated with the following conditions:

    1. Galactorrhea or amenorrhea

    2. Diseases of the hypothalamus and pituitary gland

    3. PRL-secreting pituitary tumors

    4. Acromegaly

    5. CKD

    6. Chiari–Frommel syndrome (abnormal lactation and amenorrhea following pregnancy)

    7. Ectopic production of PRL from tumors, carcinoma, and leukemia

    8. Hypothyroidism (primary)

    9. Polycystic ovary syndrome

    10. Anorexia nervosa

    11. Insulin-induced hypoglycemia

    12. Adrenal insufficiency

  2. Decreased PRL values are found in the following conditions:

    1. Sheehan syndrome (pituitary apoplexy)

    2. Idiopathic hypogonadotropic hypogonadism

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose. Fasting is required. Obtain the blood specimen between 8:00 (0800 hours) and 10:00 a.m. (1000 hours) (3–4 hours after patient has awakened). Obtain history of leakage from the breast in nonpregnant females.

  2. Have patient avoid stress, excitement, or stimulation; venipuncture itself can sometimes elevate PRL levels.

  3. If possible, discontinue all prescribed medications for 2 weeks before test.

  4. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Have patient resume normal activities.

  2. Review test results; report and record findings. Modify the nursing care plan as needed. Counsel regarding repeat testing to monitor treatment. Magnetic resonance imaging may be indicated.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

  1. Increased values are associated with newborns, pregnancy, postpartum period, stress, exercise, sleep, nipple stimulation, and lactation (breast-feeding).

  2. Drugs (e.g., estrogens, methyldopa, phenothiazines, opiates) may increase values. see Appendix E for other drugs.

  3. Dopaminergic drugs inhibit PRL secretion. Administration of L-dopa can normalize PRL levels in galactorrhea, hyperprolactinemia, and pituitary tumor. see Appendix E for other drugs.

  4. Increased levels are found in cocaine abuse, even after withdrawal from cocaine.

  5. Macroprolactin can falsely increase test results.

Clinical Alert

Levels >200 ng/mL or >200 g/L in a nonlactating female indicate an PRL-secreting tumor; however, a normal PRL level does not rule out pituitary tumor