Mastodynia due to fibrocystic disease of the breast controlled with thyroid hormone.

Nineteen patients were evaluated for breast pain and nodularity associated with fibrocystic disease. Rapid pain relief occurred in 73 of patients, with total relief in 47 percent after daily treatment with 0.1 mg of levothyroxine. Softening of breast tissue and decreased nodularity occurred within 3 months in many patients. Three patients had elevated levels of serum prolactin before treatment, with dramatic pain relief and normalization of prolactin levels after treatment. Further trials of levothyroxine in patients with mastodynia due to fibrocystic disease appear justified.