Galactorrhea is the unexpected production of milky discharge from the nipples outside of pregnancy or active breastfeeding. This discharge is typically white or cloudy and may leak spontaneously or only when the nipple is expressed. While alarming, galactorrhea is not a disease but a symptom of an underlying issue, often a hormonal imbalance. The condition is common, affecting many women, and is usually treatable once the root cause is identified.
Hormonal and Endocrine Drivers
The primary cause of galactorrhea is hyperprolactinemia, an excessive level of prolactin in the bloodstream. Prolactin is the hormone responsible for stimulating milk production, and it is secreted by the pituitary gland, located at the base of the brain. Normally, prolactin release is tightly controlled and continuously inhibited by dopamine, a neurotransmitter produced in the hypothalamus. Any disruption to this delicate balance can lead to inappropriate lactation.
Pituitary Tumors
One common internal cause is a prolactinoma. These are usually non-cancerous growths on the pituitary gland that directly overproduce prolactin, overwhelming the body’s natural dopamine inhibition. The level of prolactin elevation often correlates with the tumor size.
Hypothyroidism
An underactive thyroid gland (hypothyroidism) can indirectly stimulate prolactin release. When the thyroid gland produces insufficient thyroid hormone (T4), the hypothalamus attempts to compensate by releasing more Thyrotropin-releasing hormone (TRH). This TRH stimulates the pituitary to release prolactin, leading to galactorrhea. Identifying the specific hormonal driver is important for determining the correct management approach.
Medication and Substance Related Causes
Various medications can inadvertently cause galactorrhea by interfering with the brain’s dopamine pathways, which normally suppress prolactin release. Since dopamine acts as the primary prolactin-inhibiting factor, blocking its receptors on the pituitary gland effectively removes the inhibition on milk production, leading to drug-induced hyperprolactinemia.
Antipsychotic medications, particularly older or first-generation drugs like phenothiazines, are well-known to block dopamine receptors, causing significant prolactin elevations. Certain atypical antipsychotics, such as risperidone, are also highly associated with this side effect. The resulting prolactin levels can sometimes mimic those seen with small pituitary tumors.
Antidepressants, including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), can also cause galactorrhea, likely because increased serotonin levels indirectly modulate prolactin release. Other drugs that interfere with dopamine signaling include certain blood pressure medications (calcium channel blockers and methyldopa) and opioids.
If a medication is suspected, stopping the drug abruptly is unsafe and should only be done under medical supervision. A doctor can evaluate adjusting the dosage or switching to an alternative medication to resolve the galactorrhea while maintaining necessary treatment.
Physical and Systemic Factors
Causes of galactorrhea are not limited to internal hormonal imbalances or drug interactions; they can also arise from mechanical or systemic issues.
Nipple Stimulation
Chronic or excessive stimulation of the nipples and breasts is a direct physical trigger for prolactin release. This stimulation sends nerve signals to the hypothalamus, which responds by reducing dopamine and increasing prolactin secretion. This physical activation can occur from frequent breast self-examinations, vigorous sexual activity, or constant friction from clothing. The nerve pathways involved are the same as those activated during suckling. Reducing the source of physical stimulation is often enough to resolve the issue.
Systemic Illness and Injury
Systemic health conditions can impair the body’s ability to process and eliminate prolactin. Chronic kidney failure, for example, leads to hyperprolactinemia because the kidneys are responsible for clearing prolactin from the circulation. When kidney function is severely compromised, the hormone builds up in the blood, leading to inappropriate lactation.
Injuries to the chest wall can also trigger nerve reflexes that affect the hypothalamus. Conditions such as major chest surgery, trauma, burns, or a shingles (herpes zoster) infection on the chest can irritate the nerves. This irritation leads to a reduction in dopamine flow to the pituitary, resulting in elevated prolactin levels and subsequent galactorrhea.
Seeking Diagnosis and Medical Evaluation
If you notice persistent, milky discharge from one or both nipples, consulting a healthcare provider is necessary to determine the underlying cause. While many causes are benign, medical evaluation is required to rule out more serious conditions. Immediate attention is required if the discharge is bloody, comes from only one duct, or is accompanied by symptoms like persistent headaches or vision changes.
The diagnostic process typically begins with a thorough medical history, including a detailed review of all current medications, and a physical examination of the breasts. A simple blood test is then used to measure the level of prolactin in the blood. Since pregnancy is a common cause of lactation, a pregnancy test is also conducted.
If prolactin levels are found to be high, your doctor will likely order additional blood work, specifically to check thyroid function. If hypothyroidism is suspected, treating the thyroid condition often resolves the galactorrhea. When prolactin levels are significantly elevated and no other cause is immediately apparent, an MRI of the brain may be necessary to check for a pituitary tumor or other structural issues.