Evaluation of thyroid function in lithium-naive bipolar patients

A high prevalence of thyroid hypofunction has been found in bipolar patient s. However, the samples used in previous studies included a high percentage of patients in treatment with lithium and carbamazepine. Since the use of these drugs may explain the high prevalence of thyroid disturbances found i n bipolar patients, we designed the present study to assess thyroid functio n in a sample of bipolar patients who had not been treated previously with lithium or carbamazepine, Patients included in the sample met Research Diag nostic Criteria for bipolar affective disorder. Assessment included determi nation of serum levels for total tyroxine (T4), total triiodothyronine (T3) , and thyrotropin both basally and in response to infusion of 500 mg of Pro tilerin. The rate of thyroid hypofunction in the total sample (9.2%) was co nsiderably lower than that reported in other studies with bipolar patients undergoing lithium therapy. Five patients (9.2%) showed some thyroid hyperf uncion parameter. Our results do not show significant differences in thyroi d function indices between long-term and short-term duration of illness, be tween outpatients and inpatients, between high and low number of episodes, and between rapid- and non-rapid-cycling cases. Comparison between bipolar I and bipolar II patients shows a statistically significant difference in t he values of TSH levels, with the bipolar II group having a higher mean val ue. Our data suggest that thyroid dysfunction is not related to gender, dur ation of illness, number of episodes, or rapid-cycling course of illness. T he higher TRH-stimulated TSH levels in the bipolar II group could be consid ered a differential biological feature. (C) 1999 Editions scientifiques et medicales Elsevier SAS.