Hyperprolactinemia is a disorder in which the pituitary gland in the brain produces too much of the hormone prolactin.

Prolactin is a hormone that stimulates milk production in women. Small amounts of prolactin normally circulate in the blood of non-pregnant women. Large amounts circulate during pregnancy and right after birth.

Hyperprolactinemia (too much prolactin) can cause irregular or no ovulation, resulting in infertility. Women who have this disorder often have irregular periods and may also have some milk production (galactorrhea) even if they are not pregnant.

When the prolactin levels are high, irregularities in reproductive hormones can occur. This can result in infertility, bone density loss, visual disturbances, and headaches.

One of the most common causes of hyperprolactinemia is a small benign (non-cancerous) tumor in the pituitary gland. The pituitary gland produces prolactin and is located in the base of the brain behind the eyes. Other causes may be an underactive thyroid (hypothyroidism), or certain medications. Sometimes, the cause is unknown.

These tests may be used to confirm the diagnosis:

• Prolactin blood level: measures the amount of prolactin in your blood
• Thyroid test: diagnoses thyroid disorders; underactive thyroid can cause hyperprolactinemia

• Magnetic Resonance Imaging (MRI): uses high frequency radio waves to produce an image of the pituitary gland to detect a tumor or other abnormality
• Computerized Tomography (CT): produces a 3-dimensional image of the pituitary gland to detect a tumor or other abnormality

Treatment depends on the cause of the excessive prolactin production. Thyroid medications can be prescribed to treat an underactive thyroid. Once that is corrected, the amount of prolactin in the blood should go down to normal. If the cause is unknown or if a pituitary tumor exists, treatment with medication can reduce the prolactin level and can shrink a pituitary tumor. Once prolactin levels are in the normal range, menstrual periods become more regular and egg release (ovulation) becomes more normal. Treatment, however, will not cure the disorder. If medication is stopped, the prolactin level is likely to increase again and symptoms will probably return.