Galactorrhea · What Is It, Causes, Signs and Symptoms, and More

Galactorrhea refers to any milky nipple discharge that occurs outside of pregnancy or breastfeeding. It can occur in both genetic females and males and is typically the result of elevated prolactin levels in the blood.  

Prolactin is a hormone produced by the pituitary gland that plays an essential role in breast development and breastmilk production. Apart from milk production, high levels of prolactin inhibit the release of sex hormones, which is why breastfeeding individuals don’t typically ovulate or have menstrual periods. The release of prolactin is tightly controlled by the hypothalamus, which makes two key prolactin-regulating hormones that act on the pituitary gland: thyrotropin-releasing hormone (TRH), which increases prolactin release; and dopamine, which inhibits prolactin release and overrides the stimulatory effect of thyrotropin-releasing hormone. 

The most common cause of galactorrhea is hyperprolactinemia or elevated prolactin levels in the blood. Hyperprolactinemia can develop in a few different ways. The first is physiologic hyperprolactinemia, which happens during pregnancy and breastfeeding. Prolactin release is stimulated when the baby begins suckling at the breast, which is why touching the nipples (e.g. during sexual activity) or lesions on the chest wall can sometimes lead to galactorrhea, even in non-pregnant individuals. 

Outside of pregnancy, the most common cause of elevated prolactin are prolactinomas, which are benign tumors of the pituitary gland that release prolactin. Other causes include systemic disorders, like hypothyroidism or chronic kidney disease. In hypothyroidism, the hypothalamus tries to increase the production of thyroid hormones by releasing more thyrotropin-releasing hormone, which leads to higher prolactin levels as a side effect. In chronic kidney disease, there is decreased clearance of prolactin by the kidneys, which causes higher circulating levels in the blood. 

Another cause of hyperprolactinemia is damage to the hypothalamic-pituitary stalk, which contains the blood vessels that connect the hypothalamus to the pituitary gland. This damage can be caused by trauma, brain tumors, or brain surgery. Finally, there is medication-induced hyperprolactinemia, which is a rare side effect of antipsychotics (e.g. haloperidol, risperidone), tricyclic antidepressants (e.g. amitriptyline), SSRIs (e.g. fluoxetine, paroxetine, sertraline), metoclopramide, oral contraceptives, or methyldopa.  

Galactorrhea presents as unilateral or bilateral milky nipple discharge in a person that is not pregnant or breastfeeding. Accompanying symptoms vary depending on the underlying cause and genetic sex of the individual. For example, genetic females with hyperprolactinemia may also experience amenorrhea, which is the absence of ovulation and menstrual cycle; whereas in genetic males, symptoms may include gynecomastia, or enlargement of breast tissue, and erectile dysfunction. Both sexes can experience decreased libido and infertility. 

In cases of large prolactinomas, the tumor can compress the optic nerves as they cross behind the pituitary gland, causing headaches or vision problems. Individuals with compression symptoms typically report difficulty seeing things that are on the outermost portion of the visual field, causing a “tunnel vision” effect. 

Diagnosis of galactorrhea is based on medical history and physical examination. The first step is to distinguish galactorrhea from pathologic nipple discharge, which could be caused by breast tumors. Pathologic nipple discharge typically presents unilaterally; comes from a single duct; and tends to be bloody, serous, or purulent instead of milky or clear. Additional signs that should raise concern for malignancy include any lumps; asymmetries between breasts; or changes to the skin of the breast, nipple, or areola. 

Follow-up testing may include blood tests to help find the cause of galactorrhea, including prolactin and sex hormone levels (e.g. testosterone, estrogen) as well as blood tests to assess thyroid function (e.g. TSH, T4) and renal function (e.g. creatinine, BUN, GFR). If hyperprolactinemia is confirmed, a pregnancy test may be performed to check for a physiologic explanation. If negative, additional tests, such as magnetic resonance imaging (MRI) of the brain, may be needed to rule out a pituitary tumor or other brain lesions. Additionally, ophthalmologic evaluation may be recommended in individuals complaining of associated vision loss. 

Treatment of galactorrhea varies depending on the underlying cause. In the case of prolactinomas, it generally involves medications like cabergoline or bromocriptine, which simulate the inhibitory effect of dopamine on prolactin release. Surgery is usually considered in individuals with prolactinomas that cause compression symptoms or when medical therapy is ineffective or not tolerated. 

In people with systemic conditions, galactorrhea often resolves after treating the underlying condition; whereas for medication-induced hyperprolactinemia, treatment involves discontinuing the offending medication or switching to another one with less risk of hyperprolactinemia.  

If no identifiable cause is found and symptoms are mild, regular monitoring might be sufficient, especially if prolactin levels are normal or slightly elevated. Avoiding nipple stimulation, such as during breast self-examinations or sexual activity, can help reduce nipple discharge.