Thyroid function in treatment-resistant schizophrenia patients treated with quetiapine, risperidone, or fluphenazine

J Clin Psychiatry. 2005 Jan;66(1):80-4. doi: 10.4088/jcp.v66n0111.


Background: Thyroid dysfunction is relatively common in patients with schizophrenia, possibly related to a genetic linkage of the disorders and to antipsychotic treatment. Quetiapine has been implicated as causing some degree of thyroid function changes, yet it remains unclear as to what extent or why these changes may occur. Furthermore, the need for thyroid function monitoring in patients taking this medication is not definitive.

Method: Thyroid function was assessed in 38 adult DSM-IV-diagnosed schizophrenia patients after 6 weeks of prospective, double-blind, randomized treatment with quetiapine (400 mg/day), risperidone (4 mg/day), or fluphenazine (12.5 mg/day). Data were collected from 1997 to 2002.

Results: At baseline, the percentages of randomized patients with abnormal values were 18% (4/22) for serum T(3) resin uptake, 13% (4/30) for thyroid-stimulating hormone (TSH), and 9% (2/22) for total serum thyroxine (TT(4)), representing fairly widespread thyroid abnormalities independent of treatment group. Little change was noted in thyroid function during the 6 weeks of treatment, except for a significant decrease in TT(4) values for those taking quetiapine (p = .01). Clinically, however, no patients demonstrated any signs or symptoms of hypothyroidism during the study, nor were any significant changes in the free thyroxine index or TSH levels noted.

Conclusions: It is expected that TT(4) levels will decrease during quetiapine treatment, and this may possibly be related to competitive metabolism of thyroid hormones and quetiapine by UDP-glucuronosyltransferase. Routine monitoring of thyroid function in quetiapine-treated patients without a history of thyroid disease is not recommended.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Antipsychotic Agents / adverse effects
  • Antipsychotic Agents / therapeutic use*
  • Dibenzothiazepines / adverse effects
  • Dibenzothiazepines / therapeutic use*
  • Double-Blind Method
  • Drug Resistance
  • Female
  • Fluphenazine / adverse effects
  • Fluphenazine / therapeutic use*
  • Humans
  • Male
  • Middle Aged
  • Prospective Studies
  • Quetiapine Fumarate
  • Risperidone / adverse effects
  • Risperidone / therapeutic use*
  • Schizophrenia / drug therapy*
  • Schizophrenic Psychology
  • Thyroid Diseases / blood
  • Thyroid Diseases / chemically induced
  • Thyroid Diseases / diagnosis
  • Thyroid Function Tests / statistics & numerical data*
  • Thyrotropin / blood
  • Thyroxine / blood
  • Treatment Outcome
  • Triiodothyronine / blood


  • Antipsychotic Agents
  • Dibenzothiazepines
  • Triiodothyronine
  • Quetiapine Fumarate
  • Thyrotropin
  • Risperidone
  • Thyroxine
  • Fluphenazine