What is the next step in management of a woman with abnormal uterine bleeding and an elevated prolactin level of 90 ng/mL?

Management of Elevated Prolactin (90 ng/mL) in a Woman with Abnormal Uterine Bleeding

Order pituitary MRI imaging to evaluate for prolactinoma, as a prolactin level of 90 ng/mL strongly suggests a pituitary adenoma that requires specific treatment distinct from standard AUB management. 1

Immediate Next Steps

Confirm and Characterize Hyperprolactinemia

• Repeat prolactin measurement to exclude macroprolactinemia (biologically inactive "big-big" prolactin molecule), which can cause falsely elevated levels in normally ovulating women and does not require treatment 2
• A prolactin level of 90 ng/mL (normal <25 ng/mL) is significantly elevated and warrants investigation for a structural pituitary lesion 1

Obtain Pituitary Imaging

• MRI of the pituitary with gadolinium is the imaging modality of choice to identify and characterize a prolactinoma 3
• Prolactin levels >100 ng/mL typically indicate a macroprolactinoma (>1 cm), while levels between 25-100 ng/mL may represent either a microprolactinoma (<1 cm) or stalk compression from a non-functioning adenoma 3
• At 90 ng/mL, this patient likely has either a large microprolactinoma or small macroprolactinoma 3

Complete Endocrine Evaluation

• Verify that TSH was already checked as part of the initial AUB workup, since thyroid dysfunction can cause both hyperprolactinemia and anovulatory bleeding 4, 1
• Exclude medication-induced hyperprolactinemia by reviewing all current medications (antipsychotics, metoclopramide, SSRIs, H2-blockers) 2

Why This Matters for AUB Management

Hyperprolactinemia as the Root Cause

• Hyperprolactinemia directly causes anovulation by suppressing gonadotropin-releasing hormone pulsatility, leading to oligomenorrhea or amenorrhea with breakthrough bleeding 1, 2
• Treating the underlying prolactin disorder may completely resolve the abnormal bleeding without requiring standard hormonal contraception or surgical intervention 1
• Endocrine testing should never be omitted even when structural uterine pathology is present, because coexisting hyperprolactinemia requires specific dopamine agonist therapy 1

Treatment Implications

• Medical therapy with dopamine agonists is the initial treatment of choice for prolactinomas 3
• Cabergoline is more efficacious and better tolerated than bromocriptine for most indications, though bromocriptine has more extensive safety data in pregnancy and is preferred when fertility is the primary goal 3
• Cabergoline dosing typically starts at 0.25-0.5 mg twice weekly and is titrated based on prolactin normalization and tumor shrinkage 5

Critical Safety Considerations Before Starting Dopamine Agonists

Cardiac Screening Required

• All patients must undergo baseline cardiovascular evaluation including echocardiogram before initiating cabergoline to assess for pre-existing valvular disease 5
• If valvular disease is detected, cabergoline is contraindicated 5
• High-dose cabergoline (>2 mg/day) for Parkinson's disease is associated with cardiac valvulopathy; lower doses used for hyperprolactinemia carry less risk but still require monitoring 5

Ongoing Monitoring

• Echocardiographic monitoring every 6-12 months is recommended during cabergoline therapy, or more frequently if signs/symptoms develop (edema, new murmur, dyspnea, heart failure) 5
• Monitor for extracardiac fibrotic complications including pleural, pericardial, and retroperitoneal fibrosis with clinical assessment and periodic chest X-ray, ESR, and serum creatinine 5
• Discontinue cabergoline if echocardiogram shows new valvular regurgitation, restriction, or leaflet thickening 5

Common Pitfalls to Avoid

• Do not initiate standard AUB hormonal therapy (combined oral contraceptives, progestins, LNG-IUD) without first addressing hyperprolactinemia, as this treats the symptom rather than the underlying endocrine disorder 1
• Do not assume the elevated prolactin is incidental—at 90 ng/mL, this is the likely primary driver of anovulatory bleeding and requires targeted treatment 1, 2
• Do not delay pituitary imaging—prolactinomas account for approximately 50% of hyperprolactinemia cases and require specific management 2
• Do not overlook macroprolactinemia—confirm true hyperprolactinemia before proceeding with imaging and treatment, as macroprolactin does not cause symptoms 2

When to Refer

• Refer to endocrinology for dopamine agonist initiation, dose titration, and long-term management of prolactinoma 3
• Refer to neurosurgery if the patient has a macroadenoma with mass effect, visual field defects, or fails medical therapy 3, 2
• Coordinate with gynecology only after prolactin is normalized if AUB persists, to address any residual structural uterine causes 1