Marijuana induced gynecomastia: clinical and laboratory experience

Fourteen patients with gynecomastia appearing after heavy marijuana use have been observed over the past two yr. Patients with the onset of gynecomastia at puberty have been eliminated, and none had a history for other mammotrophic agents such as phenothiazines, digitalis, reserpine, and 'hormones'. Results have been normal for laboratory tests including bilirubin, urinary keto and hydroxycorticoids, urinary estrogen, serum prolactin, follicle stimulating hormone. Three of the patients have been able to abstain from marijuana and report diminished breast tenderness and size. Three other patients have had surgical excision of breast tissue at their request, and pathologic examination has revealed florid ductal proliferation. A laboratory experiment was undertaken to investigate this phenomenon. Male Long Evans rats were injected subcutaneously with the psychoactive component of marijuana Δ 9 tetrahydrocannabinol (THC). The marijuana extract, THC, was observed to stimulate the development of rat breast tissue, which is consistent with the clinical findings. Marijuana's endocrine role is substantiated by these experiments and by the findings of diminished plasma testosterone levels in long term marijuana users.