Prolactin is a hormone produced by a pea-sized gland at the base of your brain, called the pituitary gland. Hormones are chemical messengers that travel through your body to control various body functions. When you are pregnant, prolactin travels to your breasts to enlarge them and start milk production. After pregnancy, prolactin stimulates the release of breast milk. When you are not pregnant, prolactin travels to your ovaries where it helps control the level of your female hormone estrogen.
Causes of High Prolactin
Your pituitary gland increases in size and produces higher prolactin levels during pregnancy, which is normal. High prolactin levels outside of pregnancy are not normal, and are usually caused by a benign growth in the pituitary called a prolactin-secreting adenoma or prolactinoma. Other less common causes include:
- An underactive (hypothyroid) thyroid gland
- Certain medications used to treat high blood pressure, heartburn, severe pain (opioids), or depression
- Some herbal medications including fenugreek, goat’s rue, and red raspberry leaf
- Excessive exercise or stress
- Unknown causes
What Could High Prolactin Mean?
If you are not pregnant, it could mean you have irregular periods and have trouble getting pregnant. That’s because high levels of prolactin could suppress estrogen, which you need for normal ovulation. In fact, about 15 percent of women who struggle with infertility due to anovulation have high prolactin levels.
In addition to infertility and irregular periods, high prolactin may cause other symptoms due to low estrogen levels like dryness of your vagina, low sex drive, and bone loss (osteoporosis). Another sign may be production of breast milk outside of pregnancy. High prolactin caused by a large prolactinoma may cause headaches or double vision.
A diagnosis of high prolactin is made with a prolactin blood test. If your prolactin is high, your doctor may check your thyroid levels and ask about other possible causes. To rule out a prolactinoma, and MRI imaging study of your pituitary gland may be done.
Women who have high prolactin on a blood test but do not have any signs or symptoms may not need treatment. Treatment of hypothyroidism, changing medications, and reducing stress or exercise may reduce high prolactin for some women. High prolactin from a prolactinoma often requires medical treatment. Medications called dopamine agonists can be given. These medications decrease prolactin production and can shrink a prolactinoma. They may also help a woman with infertility become pregnant.
How Does a Prolactinoma Affect Pregnancy?
If you have been diagnosed with a prolactinoma before pregnancy, and you are on a dopamine agonist, your doctor will probably take you off this medication during pregnancy. Dopamine agonists have not been linked to any birth defects, but they have not been studied in pregnancy. Since there is only a small risk that a prolactinoma will get bigger during pregnancy, most doctors will avoid these medications.
Your doctor may ask you to watch out for signs that the prolactinoma is getting bigger, such as headaches or any vision changes. If an MRI shows an enlarging prolactinoma during pregnancy, medications may be restarted. This will usually shrink the prolactinoma. In very rare cases, surgery may be done to remove a dangerously large prolactinoma. In almost all cases, high prolactin levels can be managed and pregnancy can proceed.