What is the cause of galactorrhea (spontaneous breast milk discharge) in a female of childbearing age, possibly a new mother or someone who is breastfeeding, and how is it treated?

Galactorrhea: Causes and Treatment

In a woman of childbearing age with spontaneous breast milk discharge (galactorrhea), the most common cause is hyperprolactinemia—typically from medications or pituitary microadenomas—and treatment depends on the underlying etiology, with dopamine agonists (cabergoline preferred) for prolactinomas and medication discontinuation when drug-induced. 1, 2

Distinguishing Physiologic from Pathologic Discharge

Before evaluating for galactorrhea specifically, you must first classify the nipple discharge:

• Physiologic discharge is bilateral, from multiple ducts, non-spontaneous (requires compression), and white/green/yellow/clear in color 3
• Galactorrhea is milky discharge that is NOT due to pregnancy or lactation within the past year 2
• Pathologic discharge (NOT galactorrhea) is spontaneous, unilateral, single-duct, and bloody/serous/serosanguineous—this requires imaging workup to exclude malignancy 4, 3

If the discharge is milky and bilateral, proceed with galactorrhea evaluation; if bloody or serous, this is pathologic discharge requiring mammography and ultrasound to exclude cancer. 4, 5

Causes of Galactorrhea

The most common etiologies in order of frequency:

• Medication-induced hyperprolactinemia: Antipsychotics, metoclopramide, antidepressants, antihypertensives 1, 2
• Pituitary microadenomas (prolactinomas): Most common pathologic cause 1, 2
• Hypothyroidism: Elevated TRH stimulates prolactin release 1, 2
• Chronic renal failure: Decreased prolactin clearance 1, 2
• Physiologic causes: Nipple stimulation, stress, sleep, sexual intercourse 6
• Idiopathic: No identifiable cause despite workup 1

Diagnostic Workup Algorithm

Step 1: Rule out pregnancy

• Obtain urine or serum β-hCG in all premenopausal women 2

Step 2: Measure prolactin level

• Normal prolactin: <25 ng/mL in women 1
• Mild elevation (25-100 ng/mL): Usually medication-induced or idiopathic 2
• Moderate elevation (100-200 ng/mL): Suggests microadenoma 2
• Marked elevation (>200 ng/mL): Highly suggestive of macroadenoma 2

Step 3: Assess thyroid and renal function

• Measure TSH to exclude hypothyroidism 1, 2
• Measure creatinine to assess renal function 2

Step 4: Review medications

• Identify and discontinue causative medications if possible 1, 2
• Common culprits: risperidone, haloperidol, metoclopramide, SSRIs, tricyclic antidepressants, verapamil, methyldopa 1

Step 5: Brain MRI if hyperprolactinemia persists

• Obtain pituitary MRI with gadolinium if prolactin remains elevated after excluding medications, hypothyroidism, and renal failure 1, 2
• MRI identifies microadenomas (<10 mm) and macroadenomas (≥10 mm) 2

Treatment Based on Etiology

Medication-Induced Galactorrhea

Discontinue or switch the offending medication to an alternative with lower prolactin-elevating potential. 1, 2

• Example: Switch from risperidone to aripiprazole (lower prolactin effect) 1

Prolactinomas (Pituitary Adenomas)

Cabergoline is the preferred first-line dopamine agonist due to superior efficacy, tolerability, and twice-weekly dosing. 2

• Cabergoline: Start 0.25 mg twice weekly, titrate to 0.5-1 mg twice weekly 2
• Bromocriptine: Alternative if cabergoline unavailable; 1.25-2.5 mg daily, but more side effects 1
• Surgery (transsphenoidal resection) reserved for: patients intolerant to dopamine agonists, those with persistent hyperprolactinemia despite high-dose cabergoline, or macroadenomas with mass effect 2

Hypothyroidism

Treat with levothyroxine to normalize TSH; prolactin levels will normalize as thyroid function improves. 1

Idiopathic Galactorrhea (Normal Prolactin)

If galactorrhea is not bothersome to the patient, reassurance and observation are appropriate—no treatment needed. 1

• If bothersome: Short course of low-dose dopamine agonist (cabergoline 0.25 mg twice weekly) usually resolves symptoms 1

Special Considerations for Women of Childbearing Age

• Major duct excision should be avoided in women desiring future breastfeeding, as it may impair lactation 4
• Prolactinomas often remain stable or regress; most microadenomas do not require surgery 6
• In pregnancy: Prolactinomas may enlarge significantly and require close monitoring with visual field testing if macroadenoma present 6
• Dopamine agonists are typically discontinued once pregnancy confirmed, unless macroadenoma with visual symptoms 6

Critical Pitfalls to Avoid

• Do not assume milky discharge is benign without checking prolactin—pituitary adenomas require specific management 1
• Do not obtain MRI before checking prolactin, TSH, and creatinine—most cases are medication-induced or hypothyroidism 2
• Do not confuse galactorrhea with pathologic (bloody/serous) discharge—the latter requires imaging to exclude malignancy with 5-21% cancer risk 4
• Do not use bromocriptine as first-line when cabergoline is available—cabergoline has better efficacy and tolerability 2