The hypothalamic–pituitary–thyroid axis in patients with schizophrenia

Serum concentrations of thyroxine (T4), triiodothyronine (T3), reverse triiodothyronine (rT3) and thyrotropine (TSH) were measured in 31 acutely ill in-patients with schizophrenia before and after four weeks of treatment with the phenothiazine derivative perazine. The serum levels of all the above hormones were also determined in 19 schizophrenic patients in remission who were receiving no medication, 20 schizophrenic patients in remission taking neuroleptic drugs, and 24 patients with residual-type schizophrenia.

The serum levels of T4 of acutely ill schizophrenic patients were elevated, while those of T3, rT3 and TSH were normal. Their T4 levels showed a positive correlation with the severity of illness and the degree of clinical response to neuroleptic treatment. There was a significant fall in serum concentrations of T4 and rT3 during four weeks of drug treatment and the decrease was significantly correlated to clinical response. No abnormalities in the serum concentrations of any of the hormones measured were found in schizophrenic patients in remission or in residual-type schizophrenia.

In conclusion, our results indicate that the elevated serum levels of T4 may be specific for acutely ill schizophrenic patients and that neuroleptic medication may affect thyroid hormone metabolism, this interaction being involved in the mechanism of action of these drugs.