Abstract: AIM: To investigate changes in serum thyroid hormone levels in psychiatric patients after risperidone monotherapy or polytherapy treatment.  METHODS: Twenty-nine in-patients who received risperidone monotherapy treatment and 25 in-patients who received polytherapy treatment of risperidone and other second-generation antipsychotics were included. Changes in thyroid hormone levels after treatment were retrospectively analyzed. RESULTS: After risperidone monotherapy treatment, serum levels of free thyroxine (FT4) and total thyroxine (TT4) significantly decreased, and serum TSH levels significantly increased (changes from baseline: FT4: median －2.52 pmol/L, P<0.001; TT4: －21.17 nmol/L, P=0.012; TSH: median 0.49 mIU/L, P=0.001). After risperidone polytherapy treatment, serum levels of free triiodothyronine (FT3), total triiodothyronine (TT3) and FT4 significantly decreased, and serum TSH levels significantly increased (changes from baseline: FT3: median －0.37 pmol/L, P=0.001; TT3: median－0.17 nmol/L, P=0.008; FT4: median －2.25 pmol/L, P<0.001; TSH: median 0.97 mIU/L, P=0.029). After risperidone monotherapy treatment, moderately positive relation was found between changes in serum TT4 levels and average daily dose of risperidone. No statistical difference was found on the incidence of subclinical thyroid dysfunction between the two therapeutic regimen (6.9% vs. 12.0%, P=0.862). CONCLUSION: To avoid other disease caused by abnormal thyroid hormone levels, changes in serum thyroid hormone levels should be noticed after risperidone treatment.

Key words: risperidone, thyroid hormone, triiodothyronine, thyroxine, polytherapy