Prolactin (PRL) is a hormone responsible for lactation, breast tissue growth, and milk production. Higher than normal levels in the blood can cause certain symptoms such as irregular periods, infertility, and erectile dysfunction.
What is prolactin?
It is the hormone responsible for lactation and breast tissue growth and helps with hundreds of other processes in the body. Prolactin levels are usually low in people who are male at birth (AMAB) and in non-lactating and non-pregnant individuals. The level of this hormone usually increases in people who are pregnant or breastfeeding. Most of the prolactin is produced and secreted in the pituitary gland.
The pituitary gland is a small pea-sized gland located at the base of the brain and below the hypothalamus. It is part of the endocrine system and makes many important hormones, including prolactin. Dopamine and estrogen control the production of prolactin and its release from the pituitary gland.
The central nervous system, immune system, uterus, and mammary glands can also produce it. The following factors can contribute to the creation of prolactin in these tissues:
- Nipple stimulation
- Exercise
- Stress
How does prolactin affect my body?
It helps with hundreds of bodily functions but has two main functions.
The role of prolactin in mammary gland growth and milk production
During pregnancy, prolactin, estrogen, and progesterone stimulate breast tissue growth and milk production. PRL causes the growth of a special type of breast tissue called mammary alveoli, parts of the mammary gland where milk is produced. It also stimulates the alveolar cells of the breast to make milk components, including:
- Lactose (Carbohydrate milk)
- Casein (Milk protein)
- Lipids (Provides energy, cholesterol, and essential fatty acids)
The role of PRL in lactation and breastfeeding
After childbirth, progesterone levels decrease, increasing prolactin receptors in the mammary alveolar cells. This allows milk to be secreted through the nipple.
After childbirth, PRL levels do not remain consistently high. The levels only increase during periods of nipple stimulation through sucking by the baby. Prolactin levels remain high as long as the baby is breastfeeding. During periods when the mother does not breastfeed, PRL levels decrease, and milk production decreases. If a person does not breastfeed their baby, prolactin levels will drop to non-pregnant levels after one to two weeks.
Why is the prolactin test done?
It is important for reproductive health in both men and women. The specific function of prolactin in men is not well understood. However, PRL levels have been used to measure sexual satisfaction in both men and women. PRL-level testing can show other problems caused by this hormone.
Women
Women who have symptoms of a prolactinoma may need this test. A prolactinoma is a non-cancerous tumor in the pituitary gland that produces high prolactin levels. Symptoms of prolactinoma in women include:
- Pain or discomfort during sex
- Abnormal growth of body and facial hair
- Abnormal acne
- Unexplained headaches
- Visual impairment
- Galactorrhea, or lactation outside of childbirth or nursing
In addition, a PRL test may be needed if you have fertility problems or irregular periods. This test can also rule out other problems with the pituitary gland or hypothalamus.
Men
Men may need testing if they develop symptoms of prolactinoma. Symptoms of prolactinoma in men include:
- Reduced sex drive or fertility problems
- Erectile dysfunction
- Unexplained headaches
- Visual impairment
- Abnormal lack of body and facial hair
This test may also be used for the following:
- Examination of testicular dysfunction or erectile dysfunction
- Rule out problems with the pituitary gland or hypothalamus
What are normal prolactin levels?
The normal range for PRL levels may vary slightly in different laboratories. Look at the normal range listed on your lab report, or ask your healthcare provider if you have any questions about your results. In general, normal levels of prolactin are:
- For people assigned male at birth: less than 20 ng/ml
- For individuals assigned female at birth and not pregnant or lactating: less than 25 ng/mL
- For people who are pregnant or breastfeeding: 80 to 400 ng/ml
How is the test carried out?
A PRL test is just like a blood test. It takes a few minutes in the lab. The sample is usually collected three to four hours after waking up. Blood is taken from the arm vein.
Certain birth control pills, blood pressure medications, or antidepressants can affect test results. Tell your doctor about any medications you are taking before the test. Sleep problems, high-stress levels, and vigorous exercise before the test can also affect the results.
Prolactin and fertility
In some cases, high levels of prolactin can lead to infertility. Prolactinoma tumors can put pressure on the pituitary gland and stop the production of hormones. This condition is known as hypopituitarism. In men, this causes decreased libido and body hair loss. In women, it can lead to infertility.
Hyperprolactinemia can make it difficult for a woman to get pregnant. High prolactin levels can disrupt the natural production of estrogen and progesterone hormones. This can cause the ovaries to release eggs irregularly or stop altogether.
Medications and other treatments for prolactinoma help restore fertility in most women. If you have high prolactin levels or a prolactinoma tumor, talk to your doctor immediately about treatment.
What causes prolactin to increase?
Prolactin levels normally increase during pregnancy and breastfeeding. It may also increase slightly due to the following conditions:
- Eating a meal
- Exercise
- Physical stress, such as experiencing pain
- Sexual intercourse
- Nipple stimulation unrelated to chest feeding
- Injury to the chest area
- Epileptic seizures
This increase in prolactin is usually mild and temporary. Certain conditions and medications can cause long-term increases in prolactin levels.
What causes abnormally high levels of prolactin?
Several factors can cause higher-than-normal levels of prolactin in the blood, including:
- Prolactinoma, a pituitary gland tumor
- Certain medications
- Certain health conditions, other pituitary gland tumors
Prolactinomas
Prolactinoma is the most common cause of elevated prolactin levels in the blood. Prolactinoma is a benign tumor that forms in the pituitary gland and causes excessive production of prolactin.
Prolactinomas usually occur in people under the age of 40. They are more common in individuals assigned female at birth (AFAB) than those assigned at birth (AMAB) and occur less frequently in children and adolescents. Healthcare providers usually treat prolactinomas with medication, but they can be treated with surgery and radiation therapy.
Certain medications
The brain’s chemical dopamine helps suppress PRL production in the body. Any medications that affect the body’s production or use of dopamine can increase levels. Medications that can increase prolactin levels include:
- Some antipsychotics, such as risperidone
- Some high blood pressure medications
- Medicines that treat nausea and vomiting
- Pain relievers that contain opioids
If you have high prolactin levels due to medication, the level will usually return to normal three to four days after you stop taking the medication.
Certain health conditions
Health conditions other than prolactinoma that may cause elevated hyperprolactinemia to include:
- Kidney disease
- Hypothyroidism
- Shingles
- Other pituitary gland tumors
Large tumors located in or near the pituitary gland can increase hyperprolactinemia by reducing the effect of dopamine. Prolactin release is suppressed by dopamine, but if a tumor blocks the flow of dopamine to prolactin-producing cells, then hyperprolactinemia develops.
What causes abnormal prolactin levels?
PRL levels are usually low unless you are pregnant or breastfeeding, so the only sign of having a lower-than-normal prolactin level is not producing breast milk after delivery.
In these cases, hypopituitarism is often the cause. Hypopituitarism is a rare disease in which there is a deficiency of one, several, or all of the hormones produced by the pituitary gland. This is usually caused by abnormal pressure on the pituitary gland or damage to the pituitary gland.
Treatment for high prolactin levels
Dopamine agonists such as bromocriptine (Parlodel and Cycloset) are the most common treatment for high prolactin levels. These medications help the brain produce dopamine to control high prolactin levels. They can also shrink prolactinoma tumors.
Your doctor may recommend that you take cabergoline. Cabergoline is a newer prolactinoma treatment with milder side effects than other medications. If the medication does not help prolactinoma, the doctor may suggest radiotherapy.
The doctor may suggest surgery if the medication does not shrink the tumor. Surgery can be performed through the nose or upper skull. Surgery and medication together can bring PRL levels back to normal. Other steps that can be taken to lower prolactin levels include:
- Diet change
- Reduce stress levels
- Stop high-intensity exercise
- Avoid clothes that cause chest discomfort
- Avoiding activities and clothing that irritate the nipples too much
Taking vitamin B-6 and vitamin E supplements (Vitamin B-6 is part of the dopamine production process, and higher levels can reduce PRL levels. Vitamin E naturally prevents prolactin levels from rising).
The bottom line
Prolactin is a hormone produced by the pituitary gland in the brain. It causes the growth and development of breasts and the production of milk after the birth of a baby. Men and women normally have small amounts of it in their blood. Other hormones, such as dopamine, control PRL levels. During pregnancy, prolactin levels rise. After the baby is born, estrogen and progesterone levels suddenly decrease. But PRL levels remain high to stimulate milk production for breastfeeding.
Abnormally high prolactin can cause certain problems, such as infertility, and reduce the quality of life. If you are experiencing symptoms of hyperprolactinemia, be sure to contact your healthcare provider.
Additional questions
- What foods reduce prolactin?
Foods that lower prolactin levels generally contain zinc. Foods such as oysters, beef, turkey, and beans. It’s also important to get plenty of B6, so foods like potatoes, bananas, wild salmon, chicken, and spinach can help boost levels of this vitamin.
- Can high prolactin make you tired?
Increased levels of prolactinoma can reduce the production of other essential hormones. Decreased hormones such as cortisol can cause weakness, fatigue, and low blood pressure.
- Which is the most common cause of galactorrhea?
The most common pathological cause of galactorrhea is a pituitary tumor. Other causes include hypothalamic and pituitary stalk lesions, nerve stimulation, thyroid disorders, and chronic renal failure.
- Does high prolactin affect sleep?
Several studies have shown that PRL can induce REM sleep. It seems that stressful stimuli and conditions associated with a large increase in PRL levels may be associated with increased REM sleep.
- What cancers cause high prolactin?
Breast cancer is most strongly associated with increased prolactin levels and the receptor.
References
https://my.clevelandclinic.org/health/articles/22429-prolactin
https://www.webmd.com/a-to-z-guides/prolactin-test
https://www.healthline.com/health/prolactin#takeaway