Thyroid function in mixed and pure manic episodes.

Objectives: Associations of both overt thyroid disease as well as subclinical thyroid abnormalities with affective disorders have been well established. Similar associations have been reported with mixed mania and rapid cycling bipolar disorder. We tested for differences in overt and subclinical thyroid disease and subclinical differences in a large series of bipolar patients examined during mixed or pure manic episodes. Methods: Rates of previously diagnosed thyroid disease were compared by sex, race and manic subtype (mixed versus pure) in 443 patients. Serum thyroid stimulating hormone (TSH) and free thyroxine (FT4) concentrations obtained from patients with no clinical thyroid disease collected during manic and mixed bipolar episodes were compared using ANOVA statistics. Race was also included in the model and age was covaried. Results: Rates of thyroid disease, in particular hypothyroidism, were higher in females and white people, and increased with advancing age. No differences were noted between subjects sampled during mixed or pure manic episodes. In patients with no history of thyroid disease, serum TSH and FT4 concentrations did not differ between manic subtypes or between sexes. TSH levels however, were significantly lower in African Americans. Conclusions: We did not confirm past reports of associations of overt or subclinical thyroid disease with mixed manic episodes. African Americans had significantly lower serum TSH concentrations than white people, while FT4 levels did not differ.