Mirtazapine-Induced Gynecomastia: An Unknown Side Effect?
September 2025
in “
Journal of Psychiatry Spectrum
”

TLDR Mirtazapine can cause male breast enlargement.
This case report highlights a rare side effect of mirtazapine, an antidepressant, which is gynecomastia, or the enlargement of male breast tissue. The report details the case of a man in his late 50s who developed gynecomastia after 6 months of mirtazapine treatment. Despite normal prolactin levels and ruling out other causes, mirtazapine was identified as the probable cause using the Naranjo Adverse Drug Reaction Probability Scale. The patient underwent surgery to address the condition and was switched to fluoxetine. The report emphasizes the need for routine screening for breast enlargement in patients on mirtazapine and suggests that the decision to continue the medication should consider the risks and benefits. The exact mechanism by which mirtazapine causes gynecomastia remains unclear, though it may involve serotonin-mediated pathways.