Lab Test: Prolactin Level
- Prolactin is a hormone secreted by the anterior pituitary gland (adenohypophysis) and is controlled by prolactin-inhibiting and prolactin-releasing factors secreted by the hypothalamus as well as thyroid-releasing hormone (TRH), which can also stimulate prolactin production.
- During sleep, prolactin levels increase twofold to threefold, attaining circulating levels equaling those of pregnant women.
- Breast stimulation, pregnancy, nursing, stress, or exercise, a surge of this hormone occurs.
- Due to nocturnal circadian fluctuations, prolactin levels may rise by 50% to 100% before awakening, while levels are stable while awake In females, prolactin promotes lactation, but in its role in males has not been demonstrated.
- Adult females: 0-20 ng/mL (0-20 mcg/L)
- Pregnancy, third trimester: 95-473 ng/mL (95-473 mcg/L)
- Adult males: 0-15 ng/mL (0-15 mcg/L)
- Cord blood: 45-539 ng/mL (45-539 mcg/L)
- Newborn, 1 to 7 days: 30-495 ng/mL (30-495 mcg/L)
- Females in puberty:
- Tanner stage 1: 3.6-12 ng/mL (3.6-12 mcg/L)
- Tanner stage 2-3: 2.6-18 ng/mL (2.6-18 mcg/L)
- Tanner stage 4-5: 3.2-20 ng/mL (3.2-20 mcg/L)
- Males in puberty:
- Tanner stage 1: <10 ng/mL (<10 mcg/L)
- Tanner stage 2-3: <6.1 ng/mL (<6.1 mcg/L)
- Tanner stage 4-5: 2.8-11 ng/mL (2.8-11 mcg/L) *(PDR)
- Erectile dysfunction with suspected hyperprolactinemia
- Suspected hyperprolactinemia with amenorrhea
- Drug-Induced Hyperprolactinemia
- Suspected prolactin-secreting pituitary adenoma (prolactinoma)
- Suspected seizure disorder
- Increased levels may indicate:
- Galactorrhea, amenorrhea, prolactin-secreting pituitary tumor, infiltrative diseases of hypothalamus and pituitary stalk, metastatic cancer of pituitary gland, hypothyroidism, paraneoplastic syndrome, stress (e.g., anorexia nervosa, surgery, strenuous exercise, trauma, severe illness), seizures, mpty sella syndrome, polycystic ovary syndrome or renal failure.
- About 80% of men with hyperprolactinemia (e.g., serum prolactin level >50 ng/mL) complain of diminished libido and erectile dysfunction.
- Elevated prolactin levels inhibit pulsatile gonadotrop9in-releasing hormone (GnRH) by the hypothalamus; GnRH is needed for the secretion of pituitary gonadotropin which will in turn promote follicular development and ovulation.
- Elevated prolactin levels in the range of 25 to 200 mcg/L is suggestive of this. Serum prolactin levels parallel tumor size: macroadenomas (greater than or equal to 10 mm diameter) are associated with prolactin levels >250 mcg/L and may exceed 1000 mcg/L.
- Serum prolactin is released at the onset of a generalized tonic-clonic seizure, reaching a peak increase at 15 to 25 minutes after the event. A normal prolactin level in and of itself is insufficient to diagnose psychogenic nonepileptic seizure or to rule out the possibility of generalized tonic-clonic, complex partial, or other epileptic seizure.
- Decreased levels may indicate:
- Pituitary apoplexy (Sheehan syndrome) or pituitary destruction by tumor (craniopharyngioma)
- Drugs that may cause increased values include:
- Antipsychotic drugs (risperidone phenothiazines)
- Antinausea/antiemetic drugs
- Ergot derivatives
- Histamine antagonists
- illegal drugs (e.g., cannabis)
- Monoamine oxidase inhibitors
- Oral contraceptives
- Serotonin reuptake (antidepressants of all classes)
- Valproic acid
- Drugs that may cause decreased levels include:
- Clonidine, dopamine, ergot alkaloid derivatives, and levodopa.
- Record the use of any medication that may affect results.
- Obtain a venous blood sample.
- Apply pressure or a pressure dressing to the venipuncture site and assess the site for bleeding.
- Transfer the specimen to the laboratory as soon as possible. If a delay occurs, the specimen should be placed on ice.
- Store specimen at 4°C for up to 24 hours or freeze for long-term storage.
- Explain the procedure to the patient.
- Tell the patient that no fasting or special preparation is required.
- Inform the patient that this blood sample should be drawn in the morning.
- Freeman ME et al. Prolactin: structure, function, and regulation of secretion. Physiol Rev 2000;80:1523-631.
- Schlechte JA. Prolactinoma. N Engl J Med 2003;349:2035-41
- LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests. First ed. Montvale, NJ: Thomson PDR; 2007.
- Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5th Ed. St. Louis, Missouri. 2014.
Indications & Uses
Storage and Handling
What To Tell Patient Before & After
MESH Terms & Keywords