Prolactin Test

This test measures the amount of the hormone Prolactin in the blood. Prolactin is a hormone released by the pituitary gland. Prolactin is best known for stimulating breast development and enabling milk production in women.

In non-pregnant women and in men, abnormally high levels of prolactin may indicate a tumor in the pituitary gland or a pituitary disorder.

Prolactin Hormone Overview

Prolactin (PRL) is one of the hormones secreted by the anterior pituitary. It is regulated by the hypothalamus via the inhibitory actions of dopamine. The main function of PRL is to stimulate breast development and lactogenesis during and after pregnancy. It is PRL excess (hyperprolactinemia) that is typically associated with clinical pathology, and both males and females (most commonly) can present with symptoms including menstrual irregularity, sexual dysfunction, and infertility. Prolactin-secreting pituitary tumors known as prolactinomas are often the cause, however any process which interferes with the release of dopamine (prolactin inhibitor) can also be related to hyperprolactinemia.

The excess PRL inhibits gonadotropin-releasing hormone (GnRH) secretion by the hypothalamus resulting in decreased pituitary production of luteinizing hormone (LH) and follicular stimulating hormone (FSH). The subsequent decrease of estrogen/progesterone production in females and decreased testosterone production in males yields manifestation of several types of symptoms and/or conditions.

Interpreting Prolactin Levels

Increased prolactin

• Pregnancy and lactation
• Prolactin secreting pituitary adenoma (prolactinoma)
• Medications including amphetamines, antipsychotics, androgens, chlorpromazine, cimetidine, danazol, estrogens, fluoxetine, isoniazid, methyldopa, metoclopramide, monoamine oxidase inhibitors, opiates, phenothiazines, reserpine, tricyclic antidepressants, and verapamil. Patient medications should be known and authoritative source of drug information consulted.
• Medical conditions including hypothyroidism, renal failure, cirrhosis, and chest wall trauma/surgery
• Other pituitary tumors or parasellar tumors inhibiting dopamine release by compressing the pituitary stalk
• Idiopathic prolactinemia (a diagnosis of exclusion)
• Hypothalamus disease or disorder
• Macroprolactinemia

Decreased prolactin

• Sheehan syndrome (postpartum pituitary necrosis)
• Pituitary and extrapituitary tumors
• Treatment of a pituitary or extrapituitary tumor
• Infections ( ex: tuberculosis and histoplasmosis)
• Infiltrative diseases, such as hemochromatosis and sarcoidosis