What is the cause of unilateral galactorrhea (spontaneous milk production)?

From the Guidelines

Unilateral lactation should be evaluated for underlying pathologic causes, particularly if accompanied by spontaneous, serous, or bloodstained nipple discharge, as the risk of malignancy increases with age and presence of pathologic features 1.

Key Considerations

• Unilateral lactation can be a symptom of an underlying condition, such as intraductal papilloma or duct ectasia, which can increase the risk of malignancy 1.
• The presence of pathologic nipple discharge, such as spontaneous, serous, or bloodstained discharge, warrants further evaluation, including imaging studies and potentially biopsy 1.
• The risk of malignancy associated with pathologic nipple discharge increases with age, with studies showing a higher incidence of breast cancer in women over 40 years old 1.

Evaluation and Management

• A thorough clinical evaluation, including patient history and physical examination, is essential to determine the cause of unilateral lactation and to identify any associated pathologic features 1.
• Imaging studies, such as mammography and ultrasound, may be recommended to evaluate the breast tissue and identify any underlying lesions or abnormalities 1.
• If an underlying malignancy is suspected, a biopsy may be necessary to confirm the diagnosis and guide treatment 1.

Special Considerations

• In pregnant or lactating women, unilateral lactation with pathologic nipple discharge may require a more thorough evaluation, as the risk of malignancy cannot be ignored, even in younger women 1.
• The use of herbs or prescription medications to boost milk production should be approached with caution, as they may not address the underlying cause of unilateral lactation and may potentially mask symptoms of an underlying condition 1.

From the Research

Unilateral Lactation

• Unilateral lactation refers to the production of milk in one breast only, which can be caused by various factors, including hormonal imbalances or pituitary tumors 2, 3.
• A study published in 2011 found that mothers who practiced unilateral breastfeeding were more likely to develop breast problems in the unsuckled or less suckled breast 4.
• The study included 54 patients who breastfed their babies exclusively from one breast and 21 patients who breastfed from one breast more than the other, with 85% of the first group presenting with complaints in the unsuckled breast 4.

Causes and Risk Factors

• Prolactinomas, which are the most common type of pituitary tumor, can cause hyperprolactinemia and lead to unilateral lactation 2, 3.
• Dopamine agonists, such as bromocriptine, are commonly used to treat prolactinomas and can help reduce lactation symptoms 2, 5.
• A study published in 2014 found that women with prolactinomas who became pregnant and lactated had a higher rate of remission after pregnancy and lactation, with 41% of women achieving normal prolactin levels without medical treatment 6.

Treatment and Management

• Treatment for unilateral lactation depends on the underlying cause, with dopamine agonists being a common treatment option for prolactinomas 2, 5.
• A study published in 2012 found that bromocriptine was effective in reducing lactation symptoms in postpartum women, with a significant reduction in the proportion of women lactating compared to no treatment 5.
• In some cases, surgery or radiation therapy may be necessary to treat prolactinomas or other underlying conditions causing unilateral lactation 2, 3.