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Prolactin (PRLA)

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EPIC Test Name

PROLACTIN

EPIC Code

LAB531

Specimen Requirements

plasma
Minimum Volume:0.5 mL
Collection:Collect using standard laboratory procedures
Transport:Room Temperature ASAP
Stability:Room Temperature: 5 days at 20-25 degrees C
Refrigerated: 14 days at 2-8 degrees C
Frozen: 6 months at -20 degrees C
Container:LIT GRN
Processing/Storage:Centrifuge, pour off, and refrigerate plasma.
Rejection Causes:Hemolysis,
Insufficient Sample Volume
Notes:Samples should not be taken from patients receiving therapy with high biotin doses (i.e. > 5 mg/day) until at least 8 hours following the last biotin administration.

Methods

Chemiluminescent

Turnaround Time

SpecimenTurnaround TimeFrequency
plasma4 hours24/7

Reference Ranges

Chemiluminescent
Male RangeFemale RangeUnit
4.0-15.2 ng/mL4.7-23.3 ng/mLng/mL

Clinical Indications

Prolactin (198 aa) is a protein hormone that is secreted by the anterior pituitary, and regulated by hypothalamus, whose releasing dopamine inhibits prolactin secretion from the pituitary. Prolactin releases in response to thyrotropin-releasing hormone. Other factors can also cause prolactin concentration elevation and may include: hypothalamic disorder causing interruption in hypothalamic-pituitary portal system, certain drugs (e.g., dopamine antagonists or certain antipsychotic medication), estrogen, spinal cord injury, chronic renal disease.
Prolactin functions in initiating and maintaining lactation. In healthy subject, prolactin increases secretion in response to certain physical stimuli and conditions, e.g., sleep, stress, exercise, sexual intercourse, and hypoglycemia, and also during pregnancy, lactation, postpartum, and in an infant.
Hyperprolactinemia is the most common disorder in the hypothalamic-pituitary endocrine system. Hyperprolactinemia associated abnormalities may include prolactin-secreting pituitary adenoma (prolactinoma), functional and organic disease of the hypothalamus, primary hypothyroidism, compression of the pituitary stalk, chest wall lesions, renal insufficiency, polycystic ovarian disease, and ectopic tumors. Hyperprolactinemia induces hypogonadism by inhibiting release of gonadotropin-releasing hormone, and, consequently, FSH, LH, and testosterone in men. Male patients with hyperprolactinemia can have spermatogenic arrest, impaired motility, and sperm quality, with symptoms of reduced or impaired libido, erectile dysfunction, diminished ejaculate volume, and oligospermia, even galactorrhea. Men with prolactin-secreting pituitary adenomas occur more often than women , and more with macroadenomas than microadenoma. The former can cause visual field disturbances due to tumor pressing on the optic chiasm. Hyperprolactinemia in women can cause irregular menstrual period, anovulation, amenorrhea and galactorrhea, or galactorrhea alone, and infertility. Prolactinomas may rarely be seen in childhood or adolescence.

Additional Information

• For patients with a macroadenoma identified by MRI, but the prolactin is only modestly elevated, the patient sample should be re-measured for prolactin with x 10 and x 100 dilutions to rule out existence of a high-dose hook effect.
• For samples with slight increase of prolactin, redraw patient blood sample and repeat the tests at least two other occasions. A morning specimen taken under conditions of minimal excitement or stress to the patient, e.g., no trauma and no breast stimulation. Patient should not be on any medication that could stimulate prolactin release, as possible.
• Elevated prolactin results of patients without clinical presentation of hyperprolactinemia, presence of macroprolactinemia should be considered. Prolactin exists in circulation in three forms, they are the biologically and immunologically active monomeric (23 kDa, “little”) form accounting about 80 %, and the biologically inactive dimeric (48-56 kDa, “big”) form (5-20%) and the polymeric (> 100 kDa, “big‑big”) form accounting 0.5‑5 % with low biological activity. The immunoassays for clinical testing have low cross-activity with the big or big-big forms of prolactin. Occasionally, with the presence or absence of disease, autoantibodies (IgG) against prolactin bind to prolactin forming macroprolactin. The presence of macroprolactin increases the total prolactin concentration, as the result of lower clearance, in the absence of excess prolactin secretion by the pituitary.
• Many drugs can cause prolactin concentration increase, that may include estrogens, dopamine receptor blockers (eg, phenothiazines), dopamine antagonists (eg, metoclopramide, domperidone), alpha-methyldopa, cimetidine, opiates, antihypertensive medications, and other antidepressants and antipsychotics.

Performed

Lab
Chemistry - Downtown

Interpretative Information

• Prolactin increase occurs to patients with anovular cycles, hyperprolactinemic amenorrhea and galactorrhea, gynecomastia and azoo-spermia and prolactinoma.
• For patients treated with dopamine agonist therapies for prolactinomas, prolactin concentration should decrease substantially and reach to normal level for most cases. Failure in responding to the treatment may indicate tumors persist and be resistant to the dopamine agonist therapies. Be noted that a subset of patients may show tumor shrinkage despite persistent hyperprolactinemia. Alternative treatment should be considered for patients who have neither decreased prolactin levels nor tumor shrinkage.
• Patients with pituitary incidentaloma can also have prolactin elevation. An anterior pituitary tumor compresses the hypothalamic-pituitary portal system, hindering the delivery of the hypothalamic-prolactin-release-inhibitory hormone (PRIH) or dopamine to the lactotrophs, causing the so-called “stalk” effect or pseudoprolactinoma. In patients with prolactinoma, a treatment with a dopamine agonist should lower prolactin concentrations, whereas, it will not suppress prolactin concentration in case of pseudoprolactinoma.
• Thyrotropin (TSH) should be measured in patients suspected of a prolactinoma, to rule out primary hypothyroidism; in rare cases of severe primary hypothyroidism, TRH will promote release of prolactin.
• A pregnancy test should be performed in women of reproductive age, pregnancy causes hyperprolactinemia.
• Patients with pregnancy and suspected to have prolactinomas, their prolactin results are uninterpretable, refer to diagnostic measures.

CPT

84146

LOINC

2842-3

References

1. Smith CR, Norman MR. Prolactin and growth hormone: molecular heterogeneity and measurement in serum. Ann Clin Biochem 1990;27:542-50.
2. Sturk A, Sanders GT: Macro enzymes: prevalence, composition, detection and clinical relevance. J Clin Chem Clin Biochem. 1990;28:65-81. PMID 2184194
3. Kaye TB: Hyperprolactinemia. Causes, consequences, and treatment options. Postgrad Med. 1996;99:265-8. PMID 8650091
4. Hattori N. Macroprolactinemia: a new cause of hyperprolactinemia. J Pharmacol Sci. 2003;92:171-7. PMID 12890882
5. Suliman AM, Smith TP, Gibney J, et al.: Frequent misdiagnosis and mismanagement of hyperprolactinemic patients before the introduction of macroprolactin screening: application of a new strict laboratory definition of macroprolactinemia. Clin Chem. 2003;49:1504-9. PMID 12928232
6. Toldy E, Locsei Z, Szabolcs I, et al. Macroprolactinemia: the consequences of a laboratory pitfall. Endocrine. 2003;22:267-73. PMID 14709800
7. Molitch ME. Pituitary tumours: pituitary incidentalomas. Best Pract Res Clin Endocrinol Metab. 2009;23:667-5. PMID 19945030
8. Orija IB, Weil RJ, Hamrahian AH. Pituitary incidentaloma. Best Pract Res Clin Endocrinol Metab. 2012;26:47-68. PMID 22305452
9. Agarwal M, Das A, Singh AS. High-dose hook effect in prolactin macroadenomas: a diagnostic concern. J Hum Reprod Sci. 2010;3:160-1.
10. Casaneuva FF, Molitch ME, Schlecte JA, et al: Guidelines of the Pituitary Society for the diagnosis and management of prolactinomas. Clin Endocrinol. 2006;65:265-73.
11. Melmed S, Casanueva FF, Hoffman AR, et al: Diagnosis and treatment of hyperprolactinemia: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96:273-88.

Contact Information

Chemistry - Downtown: (315)464-4460
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