Prolactinoma

How prolactinoma affects the body

Prolactin's main role is to stimulate breast milk production. High levels suppress gonadotropin-releasing hormone, lowering estrogen in women and testosterone in men. This explains most symptoms. A large tumor can also press on surrounding structures, especially the optic nerves above the pituitary.

Symptoms

Women

• irregular, light or absent periods (amenorrhea)
• milky nipple discharge (galactorrhea) when not breastfeeding
• infertility
• vaginal dryness and pain during sex
• low libido
• bone thinning from low estrogen

Women often notice symptoms early, so prolactinomas are usually found when small.

Men

• low sex drive and erectile dysfunction
• infertility and low sperm count
• breast enlargement, rarely milk discharge
• reduced muscle mass and energy

Men often attribute symptoms to aging, so tumors may be large by diagnosis.

Symptoms from tumor size (macroprolactinoma)

• headaches
• loss of peripheral vision, often both outer fields
• double vision
• reduced function of other pituitary hormones, causing tiredness, low thyroid or low cortisol

Causes

The cause is unknown in most cases. Prolactinomas are more common in women aged 20 to 50. Rarely, they are part of multiple endocrine neoplasia type 1 (MEN1) or familial pituitary tumor syndromes.

Other causes of high prolactin

Not all high prolactin is a prolactinoma. Doctors check for:

• pregnancy and breastfeeding
• medicines: antipsychotics (especially risperidone), metoclopramide, some antidepressants, opioids, estrogen
• hypothyroidism
• kidney or liver disease
• other pituitary tumors pressing on the stalk (stalk effect)
• chest wall injury, shingles, or nipple stimulation
• macroprolactin, an inactive large form of prolactin that can cause falsely high results

See hyperprolactinemia.

Diagnosis

• blood prolactin level: very high levels (often over 200 ng/mL) strongly suggest a macroprolactinoma
• pregnancy test, thyroid function, kidney and liver tests
• pituitary MRI with contrast
• other pituitary hormones
• visual field test for larger tumors
• bone density scan if hormone levels have been low for a long time

Treatment

Medicine (first choice)

• cabergoline: usually taken once or twice a week; normalizes prolactin and shrinks the tumor in most people
• bromocriptine: taken daily; often preferred around conception

Side effects include nausea, dizziness, headache and, rarely, impulse-control problems or mood changes. High doses used for Parkinson's disease have been linked to heart valve problems, so echocardiograms may be done for people on long-term high doses.

Some people with small tumors and stable prolactin for at least 2 years on treatment can try stopping medicine under supervision.

Surgery

Transsphenoidal surgery through the nose is used if medicines are not tolerated or not effective, for pituitary apoplexy, or sometimes for small tumors by patient choice.

Radiation

Rarely needed, for tumors that do not respond to medicine and surgery.

No treatment

Small tumors without symptoms, or in women past menopause without troublesome symptoms, may be monitored.

Pregnancy and prolactinoma

Treatment usually restores fertility. Medicine is often stopped once pregnancy is confirmed for small tumors. Macroprolactinomas can grow during pregnancy, so vision and symptoms are monitored and medicine may be continued or restarted.

Outlook

Most prolactinomas are well controlled with medicine. Symptoms such as missed periods and low libido typically improve within weeks to months of normal prolactin. Long-term follow-up with blood tests and periodic MRI is recommended.

Frequently asked questions

What are the symptoms of a prolactinoma?

In women, symptoms include irregular or absent periods, milky nipple discharge and infertility. In men, low sex drive, erectile dysfunction and infertility are common. Large tumors can cause headaches and loss of side vision.

Is a prolactinoma a brain tumor?

It is a tumor of the pituitary gland, which sits at the base of the brain but is not brain tissue. Prolactinomas are almost always benign and do not spread. They are usually treated with medicine rather than surgery.

Can a prolactinoma go away?

Medicine shrinks most prolactinomas and normalizes prolactin. Some small tumors remain controlled after medicine is stopped, and some shrink after pregnancy or menopause. Others need long-term treatment.

Can you get pregnant with a prolactinoma?

Yes. Treatment with cabergoline or bromocriptine usually restores ovulation and fertility. Your endocrinologist will plan how to manage medicine and monitoring during pregnancy, particularly for larger tumors.