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Macroprolactin Blood Test

The Macroprolactin Blood Test helps determine the causes of high prolactin levels in the blood.

Test Code: 500324

CPT Code: 84146(x2)

Also Known As: Macroprolactin by PEG; Macroprolactin, Serum


Electrochemiluminescence Immunoassay (ECLIA)

Specimen Type: Blood


No special preparation is required.

Test Results:

5-10 days. May take longer based on weather, holiday, or lab delays.


What is the purpose of this test?

Order this Macroprolactin Blood Test, which helps determine the causes of high prolactin levels in the blood. Prolactin (PRL) is a hormone made by the pituitary gland at the base of the brain. Prolactin is an essential hormone for developing certain female physical features and reproductive functions, such as growing breast and breast milk production in women or anyone with ovaries. Prolactin levels are generally high for pregnant women and new mothers. However, levels usually are low for men and nonpregnant women. Prolactin's normal function in men or anyone with testes is currently unknown.


However, macroprolactin is a non-bioactive protein isoform of prolactin found in small trace amounts in blood serum. It is usually comprised of a prolactin monomer and an IgG molecule with a prolonged clearance rate similar to immunoglobulins. Moreover, this isoform is clinically non-reactive but interferes with immunological assays used to detect prolactin. Therefore, macroprolactin is vital as some lab tests will see macroprolactin as prolactin. This misinterpretation leads to a falsely elevated prolactin level. Furthermore, this can also lead to misdiagnosis of hyperprolactinemia in some people, especially those with symptoms such as infertility and menstrual problems. Certain chemicals, such as polyethylene glycol, remove macroprolactin from the body.


What conditions cause abnormal prolactin levels?

Abnormally high prolactin levels may indicate an underlying health condition, such as a tumor of the pituitary gland tumor known as prolactinoma. This benign (noncancerous) tumor causes the pituitary gland to produce too much prolactin. While these tumors are noncancerous, if left untreated, they can cause damage to surrounding tissues.


Overproduction of prolactin can cause lactation in men and women who are nonpregnant or not breastfeeding. In women, too much prolactin can also cause menstrual irregularities and infertility. In addition, it can lead to lower sex drive and erectile dysfunction (ED) in men. Commonly called impotence, ED is the incapability to get or sustain an erection.


Other conditions that may cause abnormal prolactin levels may include:


  • Hypothyroidism
  • A disease that affects the hypothalamus area of the brain, which controls the pituitary gland and other body functions.
  • Liver disease


When should I order a Macroprolactin Blood Test?

Individuals may order this test if they have experienced symptoms associated with excess prolactin. Common signs or symptoms of a prolactinoma may include:


  • Production of breast milk if you are not pregnant or breastfeeding
  • Nipple discharge
  • Irregular periods
  • Infertility
  • Breast tenderness
  • Fatigue
  • Headaches
  • Vision problems
  • Low sex drive
  • Erectile dysfunction or "ED"
  • Muscle pain

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