Recently, there is an interest on the possible association between quetiapine and hypothyroidism. the aim of this study is to critically review all the reported cases in the international literature.

A Medline search for all studies dealing with quetiapine induced hypothyroidism was carried out from January 1997 to June 2008.

Published literature on quetiapine's impact on thyroid function consists of 1 double-blind study, 1 observational study, 2 open studies, 3 case reports and data from the product monograph. A study on elderly psychotic patients revealed only small decreases in T4 levels, while another one in adolescents show trends for decrease in T4 and a marked increase in TSH. an observational study of thyroid function in patients treated with quetiapine and other antipsychotics, found a decrease in T4 with no changes in TSH and T3 and another one only slight increases in TSH. in the case reports all patients excibited clinical hypothyroidism. in one case there was a positive history for hypothyroidism, while in another one the patient had experienced lithium induced hypothyroidism in the past. According to quetiapine manufacturer 0.4% of the patients experienced TSH increases with half of them requiring thyroid replacement treatment. in studies, where quetiapine was adjunct to lithium or divalproate, 12% of patients had elevated TSH levels.

We suggest a careful thyroid monitoring for patients initiating quetiapine, since hypothyroidism may emerge and masquerade psychopathologic manifestations. However, there is an open question whether thyroid dysfunction is a permanent or reversible condition.