Is tamoxifen (tamoxifen) effective for treating gynaecomastia?

Tamoxifen for Gynecomastia

Tamoxifen is highly effective for treating gynecomastia, with approximately 90% of patients experiencing complete resolution of symptoms at a dose of 10-20mg daily for 3-6 months. 1

Efficacy and Evidence

Tamoxifen has demonstrated excellent results in the management of gynecomastia:

• A 10-year prospective cohort study showed 90.1% of patients had complete resolution of gynecomastia with tamoxifen therapy 1
• Another study reported 83.3% resolution of breast mass and 84% resolution of tenderness with tamoxifen 20mg daily for 6-12 weeks 2
• Mastodynia (breast pain) typically disappears within 3 months of starting treatment 3

Dosing and Duration

The optimal regimen based on available evidence:

• Starting dose: 10-20mg daily
• Duration: 3-6 months
• Follow-up: Evaluation at 3 months to assess response

Factors Affecting Treatment Response

Several factors influence the likelihood of successful treatment:

1. Size of gynecomastia:

   • Smaller gynecomastias (<4cm) have better response rates (90%) compared to larger ones (>4cm) (52%) 3

2. Duration of gynecomastia:

   • Gynecomastia present for less than 2 years responds better (70%) than those present for more than 2 years (56%) 3

3. Type of gynecomastia:

   • "Lump" type gynecomastia (retro-areolar) responds better (100%) than "fatty" diffuse type (62.5%) 2

4. Etiology:

   • Drug-induced gynecomastia (particularly from antiandrogens) shows excellent response 3

Safety Profile

Tamoxifen is generally well-tolerated in males with gynecomastia:

• Minimal side effects reported across studies
• Rare adverse events include calf tenderness 4, diarrhea, and flushing 3
• No long-term side effects observed in a study with 36-month follow-up 5

Treatment Algorithm

1. Confirm diagnosis of idiopathic or physiological gynecomastia (rule out secondary causes)
2. Initiate tamoxifen at 10-20mg daily
3. Evaluate at 3 months for resolution of pain and reduction in breast tissue
4. Continue for full course (3-6 months) if responding
5. Consider surgical options only for the small percentage of patients who fail to respond to medical therapy

Practical Considerations

• Tamoxifen should be considered as first-line therapy before contemplating surgery 4
• Patients with painful gynecomastia are particularly good candidates for tamoxifen therapy
• Relapse may occur in approximately 27% of cases after treatment cessation 3
• Patients with larger (>4cm) or long-standing (>2 years) gynecomastia should be counseled about potentially lower success rates but should still be offered a trial of tamoxifen

Tamoxifen represents a safe, effective, and non-invasive approach to treating gynecomastia with high success rates, particularly for painful, recent-onset, and retro-areolar "lump" type presentations.