Prolactin blood test
A prolactin blood test allows you to check the level of prolactin in your blood. Prolactin is a hormone produced by the pituitary gland that plays a role in processes such as breast milk production, fertility, and the body's production of sex hormones. A prolactin test may be relevant in cases of irregular or absent menstruation, difficulty conceiving, unexpected breast milk secretion, reduced libido, or erectile dysfunction. The test may also be part of a hormonal evaluation if there is a suspicion of pituitary gland dysfunction.
Why test for prolactin?
Prolactin is primarily analyzed when symptoms linked to elevated prolactin levels—a condition known as hyperprolactinemia—are present. High prolactin levels can affect sex hormone production, thereby impacting menstruation, fertility, and sexual function. In women, high prolactin can cause irregular or absent menstruation, difficulty conceiving, reduced libido, and galactorrhea (milk secretion unrelated to pregnancy or breastfeeding).
In men, elevated prolactin can lead to reduced libido, erectile dysfunction, impaired fertility, lowered testosterone levels, and in some cases, breast enlargement (gynecomastia).
Symptoms of high prolactin
Elevated prolactin levels do not always cause symptoms.
When symptoms occur, they are often due to prolactin affecting the body's production of sex hormones.- Irregular or absent menstruation.
- Difficulty conceiving.
- Milk secretion unrelated to pregnancy or breastfeeding.
- Reduced sex drive.
- Erectile dysfunction.
- Reduced fertility.
Significant changes in the pituitary gland can also cause headaches and visual disturbances. Such symptoms should be further investigated by a healthcare professional.
What causes high prolactin levels?
There are several possible causes for high prolactin levels. Prolactin levels can rise temporarily, so an elevated result does not necessarily indicate an underlying medical condition.
Causes of elevated prolactin include:
- stress.
- pregnancy and breastfeeding.
- sleep and having a blood sample taken shortly after waking up.
- certain medications, such as some psychiatric drugs.
- high estrogen levels.
- hypothyroidism.
- prolactinoma or other abnormalities in the pituitary region.
- other endocrine disorders.
In some cases, an elevated laboratory result may be due to so-called macroprolactin. This is a form of prolactin with a higher molecular mass that is generally considered to have low biological activity. If necessary, supplementary analysis can be used to investigate this.
Is a high prolactin level dangerous?
A slightly elevated prolactin level does not necessarily indicate disease. Stress, sleep, medication, and other temporary factors can affect the level. If prolactin levels remain high or are markedly elevated, further investigation may be required to determine the cause. Prolonged elevation of prolactin can affect sex hormone levels and lead to issues such as menstrual irregularities, reduced fertility, and sexual dysfunction. If sex hormone levels remain low for an extended period, bone mass may also be affected. One possible cause of markedly elevated prolactin is a prolactinoma, a usually benign, prolactin-producing tumor in the pituitary gland. Larger tumors in the pituitary region can also cause headaches or visual disturbances by affecting nearby structures.
Reference ranges for prolactin
To interpret the result of a prolactin test, the result is compared with the laboratory's reference range. Reference values can vary between different laboratories and analysis methods. For analysis performed by Unilabs, the following reference ranges apply:
- Women: 70–350 mIU/L
- Men: 60–260 mIU/L
A value outside the reference range does not in itself necessarily indicate disease. Prolactin levels must be evaluated in conjunction with factors such as symptoms, medications, pregnancy, breastfeeding, and the conditions under which the sample was taken.
Before prolactin testing
Prolactin follows a circadian rhythm, with levels being higher during the night. Elevated levels can persist for the first few hours after waking. Therefore, you should have been up and about for at least three hours prior to the test. Stress can also temporarily raise prolactin levels and should be avoided before the test. Medications can also affect the results. Never alter or discontinue prescribed medication on your own prior to the test.
What happens if prolactin levels are elevated?
If the prolactin level is elevated, the result must be evaluated alongside symptoms, medications, and other relevant factors. In some cases, a repeat test may be required to check whether the prolactin level remains elevated. If levels remain high, further tests or examinations may become relevant. Depending on the results and symptoms, the investigation may, for example, be supplemented with additional hormone tests, analysis of macroprolactin, or an examination of the pituitary gland.
What does low prolactin mean?
Low prolactin levels are significantly less common and usually have less clinical significance than elevated levels. Very low prolactin levels can occur in cases of impaired pituitary function and must then be evaluated in conjunction with other hormone levels and any symptoms.
