Prolactin

Synonym/Acronym

luteotropic hormone, lactogenic hormone, lactogen, HPRL, PRL.

Rationale

To assess for lactation disorders and identify the presence of prolactin-secreting tumors to assist in diagnosing disorders such as lactation failure.

Patient Preparation

There are no fluid, activity, or medication restrictions unless by medical direction. Instruct the patient to fast for 12 hr before specimen collection because hyperglycemia can cause a short-term increase in prolactin levels. Specimen collection should occur between 0800 and 1000.

Normal Findings

Method: Chemiluminescent Immunoassay.

Age	Conventional Units	SI Units (Conventional Units × 1)
Males (all ages) and prepubertal females	2.1–17.7 ng/mL	2.1–17.7 mcg/L
Females age 10 yr–adult	2.8–29.2 ng/mL	2.8–29.2 mcg/L
Pregnant	5.3–215.3 ng/mL	5.3–215.3 mcg/L
Postmenopausal	2.4–24 ng/mL	2.4–24 mcg/L

Critical Findings and Potential Interventions ⬆ ⬇

Overview ⬆ ⬇

(Study type: Blood collected in a gold-, red-, or red/gray-top tube; related body system: Endocrine and reproductive systems. Specimen should be tightly capped and transported in an ice slurry.)

Prolactin is a hormone secreted by the pituitary gland. It is normally elevated in pregnant and lactating patients. The main function of prolactin is to induce and sustain milk production in lactating women. Prolactin levels rise late in pregnancy, peak with the initiation of lactation, and surge each time a lactating woman breastfeeds. Prolactin levels are highest at night during sleep and shortly after awakening. Levels are known to increase during periods of physical and emotional stress. Elevated prolactin levels are also known to affect fertility by inhibiting secretion of gonadotropin-releasing hormone from the hypothalamus, thereby also inhibiting secretion of luteinizing hormone and follicle-stimulating hormone from the pituitary gland and suppressing ovulation. Reduced fertility during lactation offers some natural protection against pregnancy. The function of prolactin in men and nonpregnant women is unknown, but there is an association between high levels and infertility.

Indications ⬆ ⬇

Assist in the diagnosis of primary hypothyroidism, as indicated by elevated levels.
Assist in the diagnosis of suspected tumor involving the lungs or kidneys (elevated levels indicating ectopic prolactin production).
Evaluate failure of lactation in the postpartum period.
Evaluate sexual dysfunction of unknown cause in men and women.
Evaluate suspected postpartum hypophyseal infarction (Sheehan syndrome), as indicated by decreased levels.

Interfering Factors ⬆ ⬇

Drugs and other substances that may increase prolactin levels include amitriptyline, amoxapine, benserazide, butaperazine, butorphanol, carbidopa, chlorpromazine, cimetidine, clomipramine, desipramine, diethylstilbestrol, enalapril, enflurane, fenoldopam, flunarizine, fluphenazine, fluvoxamine, furosemide, growth hormone–releasing hormone, haloperidol, hexarelin, imipramine, insulin, interferon, labetalol, loxapine, megestrol, mestranol, methyldopa, metoclopramide, molindone, morphine, nitrous oxide, oral contraceptives, oxcarbazepine, parathyroid hormone, pentagastrin, perphenazine, phenytoin, pimozide, prochlorperazine, ranitidine, reserpine, sulpiride, thiethylperazine, thioridazine, thiothixene, thyrotropin-releasing hormone, trifluoperazine, trimipramine, tumor necrosis factor, verapamil, and zometapine.
Drugs and other substances that may decrease prolactin levels include anticonvulsants, apomorphine, bromocriptine, cabergoline, calcitonin, cyclosporine, dexamethasone, levodopa, metoclopramide, morphine, nifedipine, octreotide, ranitidine, rifampin, ritanserin, ropinirole, secretin, and tamoxifen.
Prolactin secretion is subject to diurnal variation with highest levels occurring in the morning.
Episodic elevations can occur in response to sleep, stress, exercise, hypoglycemia, and breastfeeding.

Potential Medical Diagnosis: Clinical Significance of Results ⬆ ⬇

Increased In

Adrenal insufficiency (secondary to hypopituitarism)
Amenorrhea (pathophysiology is unclear)
Anorexia nervosa (pathophysiology is unclear)
Breastfeeding (stimulates secretion of prolactin)
Chiari-Frommel and Argonz–Del Castillo syndromes (endocrine disorders in which pituitary or hypothalamic tumors secrete excessive amounts of prolactin)
Chest wall injury (trauma in this location can stimulate production of prolactin)
Chronic kidney disease (related to decreased renal excretion)
Decreased muscle mass
Ectopic prolactin-secreting tumors (e.g., lung, kidney)
Galactorrhea (production of breast milk related to prolactin-secreting tumor)
Hypogonadism (males)
Hypothalamic and pituitary disorders
Hypothyroidism (primary) (related to pituitary gland dysfunction)
Impotence (men)
Infertility
Loss of libido
Oligomenorrhea
Osteoporosis
Pituitary tumor
Polycystic ovary (Stein-Leventhal) syndrome
Pregnancy
Shingles
Stress (stimulates secretion of prolactin)
Surgery (pituitary stalk section)

Decreased In

Sheehan syndrome (severe hemorrhage after obstetric delivery that causes pituitary infarct; secretion of all pituitary hormones is diminished)

Nursing Implications ⬆

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

Explain that a blood sample is needed for the test.
Discuss how this test can assist in evaluating breastfeeding hormone level.

After the Study: Implementation & Evaluation Potential Nursing Actions

Treatment Considerations

Interventions/actions include the following: Answer any questions or address any concerns voiced by the patient or family. Be sensitive to feelings of inadequacy related to inability to breastfeed. Refer to a lactation specialist as appropriate. Discuss prognosis and therapeutic interventions associated with altered prolactin level.

Clinical Judgement

Consider how to overcome objections to alternate methods of infant feeding.

Follow-Up Evaluation and Desired Outcomes

Understands that depending on the results of this procedure, additional testing may be performed to evaluate or monitor disease progression and determine the need for a change in therapy.