Sorted By Test Name - Mayo Medical Laboratories

PRL
8690
controlling prolactin secretion is hypothalamic dopamine, which inhibits pituitary prolactin secretion. In
normal individuals, the prolactin level rises in response to physiologic stimuli, such as sleep, exercise,
nipple stimulation, sexual intercourse, hypoglycemia, postpartum period, and birth. Pathologic causes of
hyperprolactinemia include prolactin-secreting pituitary adenoma (prolactinoma), functional and organic
disease of the hypothalamus, primary hypothyroidism, section compression of the pituitary stalk, chest
wall lesions, renal failure, and ectopic tumors. Prolactinomas are 5 times more frequent in females than
males. Prolactin-secreting macroadenomas (>10 mm in diameter) can sometimes produce exceedingly
high serum prolactin concentrations that may paradoxically result in falsely-low prolactin concentrations
when measured by immunometric assays. In such situations, very high concentrations of prolactin saturate
both the capture and signal antibodies in the assay, block formation of the capture
antibody-prolactin-signal antibody "sandwich," and result in falsely-decreased prolactin results (referred
to as the high-dose hook effect). With such tumors, serum prolactin levels may be falsely decreased into
the normal reference interval, potentially resulting in inappropriate patient management. Dilution of the
specimen eliminates the analytic artifact in these cases.
Useful For: Identifying patients with pituitary macroprolactinomas Quantifying prolactin in specimens
where the high-dose hook effect is suspected (eg, presence of pituitary adenoma with symptoms of
prolactinoma, and lower than expected prolactin level)
Interpretation: Significantly increasing concentrations of prolactin, obtained after dilution of the
serum, is consistent with high concentrations of prolactin secreted by functional macroprolactinomas.
Serum prolactin levels >250 ng/mL are usually associated with prolactin-secreting tumors, whereas
moderately increased levels of serum prolactin are not a reliable guide for determining whether a
prolactin-producing pituitary adenoma is present. Slight nonlinearities detected in the prolactin dilution
series may indicate interference by macroprolactin (prolactin bound to immunoglobulin). In these
situations, patients are asymptomatic. Apparent hyperprolactinemia attributable to macroprolactin is a
frequent cause of misdiagnosis and mismanagement of patients.
Reference Values:
Males: 3-13 ng/mL
Females: 3-27 ng/mL
Clinical References: St-Jean E, Blain F, Comotois R: High prolactin levels may be missed by
immunoradiometric assay in patients with macroprolactinomas. Clin Endocrinol 1996 Mar;44(3):305-309
Prolactin, Serum
Clinical Information: Prolactin is secreted by the anterior pituitary gland and controlled by the
hypothalamus. It is structurally related to growth hormone (GH), but has few, if any, of the physiological
effects of GH. The major chemical controlling prolactin secretion is dopamine, which inhibits prolactin
secretion from the pituitary. The only definitively known physiological function of prolactin is the
stimulation of milk production. In normal individuals, the prolactin level rises in response to physiologic
stimuli such as sleep, exercise, nipple stimulation, sexual intercourse, hypoglycemia, postpartum period,
and also is elevated in the newborn infant. Pathologic causes of hyperprolactinemia include
prolactin-secreting pituitary adenoma (prolactinoma, which is 5 times more frequent in females than
males), functional and organic disease of the hypothalamus, primary hypothyroidism, section compression
of the pituitary stalk, chest wall lesions, renal failure, and ectopic tumors. Hyperprolactinemia often
results in loss of libido; galactorrhea, oligomenorrhea or amenorrhea, and infertility in premenopausal
females; and loss of libido, impotence, infertility, and hypogonadism in males. Postmenopausal and
premenopausal women, as well as men, can also suffer from decreased muscle mass and osteoporosis.
The latter can sometimes be dramatic in a small subgroup of women who develop severe and acute onset
postpartum osteoporosis that remits with cessation of breastfeeding and medical suppression of
hyperprolactinemia.
Useful For: Aiding in evaluation of pituitary tumors, amenorrhea, galactorrhea, infertility, and
hypogonadism Monitoring therapy of prolactin-producing tumors
Interpretation: In males, prolactin levels >13 ng/mL are indicative of hyperprolactinemia. In women,
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