What Causes Low and High Prolactin Levels?

There may be a number of causes of low or high levels of prolactin, including: Sheehan's syndrome, smoking, retained placental fragments, prolactinoma (pituitary tumor), and hypothyroidism or underactive thyroid.

Prolactin, or milk hormone, is the hormone that causes breasts to grow. It is produced by the pituitary gland located at the bottom of the brains of both men and women. Prolactin is also responsible for the creation of breastmilk after a baby is born and 300 other functions.

When there is too much prolactin in the blood of a man or woman who is not pregnant, it is called hyperprolactinemia. People who have this condition amount to a third of all women in their childbearing years. Although these women have healthy ovaries (the reproductive organs that carry a woman’s eggs/ova) they experience irregular periods.

A person with low prolactin levels is said to have hyperprolactinemia, or prolactin deficiency. Lower levels of prolactin usually do not need medical treatment.

Women who have low levels of prolactin in the blood may experience the following:

• Delayed puberty
• Menstrual disorders
• Infertility, and subfertility
• Inadequate lactation

Although some people who have high prolactin levels don’t show any signs and symptoms, both men and women may have difficulty having children and decreased desire for sex.

Other signs and symptoms include:

In men

• Erectile dysfunction—trouble getting or keeping an erection
• Breast enlargement, also called gynecomastia
• Decreased muscle mass and body hair

In women

• Vaginal dryness, leading to pain during intercourse
• Problems with menstruation—having no periods or irregular periods
• Production of breast milk when not pregnant or nursing

Women with high prolactin levels may also experience galactorrhea. A woman who has this condition may find it difficult to get pregnant. Her breasts may also start producing milk while she is not pregnant. Ninety percent of women with galactorrhea also have hyperprolactinemia.

There may be a number of causes of low levels of prolactin, including the following.

Sheehan’s syndrome

A condition that causes an inability to breastfeed.

Smoking

There is evidence that the reduction of breast milk in women who smoke cigarettes may be linked to an effect of nicotine on the production of prolactin.

Retained placental fragments

The placenta contains hormones that are known to decrease prolactin levels.

Prolactinoma (pituitary tumor)

A non-cancerous growth or tumor on the pituitary gland. The tumor can be large or small, and it produces high levels of prolactin. Prolactinomas occur more in women than in men but rarely in children.

Hypothyroidism or underactive thyroid

If you have this condition, your thyroid gland does not produce enough thyroid hormone.

Some other common causes are:

• Medicines given for depression, psychosis, and high blood pressure
• Herbs, including fenugreek, fennel seeds, and red clover
• Irritation of the chest wall (from surgical scars, shingles, or even a too-tight bra)
• Stress or exercise (usually excessive or extreme)
• Certain foods
• Nipple stimulation
• Birth control pills

A prolactin test measures the level of prolactin in your blood. The following are indications that you should talk to your doctor about doing a PRL.

If you are a woman:

• Production of breast milk if you are not pregnant or breastfeeding
• Nipple discharge
• Headaches
• Changes in vision
• Irregular periods
• Periods that have stopped completely before the age of 40, known as premature menopause
• Infertility
• Breast tenderness

If you are a man:

• Nipple discharge
• Breast enlargement
• Low sex drive
• Erectile dysfunction
• Decrease in body hair

Apart from the prolactin levels test, your doctor may conduct blood tests to measure levels of prolactin. If you just had a meal or are stressed, your prolactin levels might show up higher. In such a case, your doctor will have you fast and relax, then repeat the test.

Doctors will also ask about other conditions and medication use, and rule out pregnancy. Other advanced tests may include a scan of your brain through magnetic resonance imaging (MRI) to check for a tumor of the pituitary gland.

Your doctor will treat you according to the cause of the condition. Usually, your doctor will prescribe thyroid replacement medicine to bring your prolactin levels back to normal. If a medicine is the cause, your doctor will help you find something to get your levels back to normal. If a cause was not found, there is no need to get treated for the condition.

A woman with hyperprolactinemia may continue taking birth control pills to prevent pregnancy or make their periods regular. However, women who cannot create estrogen due to high levels of prolactin should get treated.

Bromocriptine is taken 2-3 times a day and Cabergoline is long-acting and used twice weekly. Surgery is sometimes needed if the tumor in the pituitary gland is affecting vision.