Rapid cycling bipolar affective disorder: lack of relation to hypothyroidism

Thyroid indices were measured after an extended period of medication-free evaluation averaging 6 weeks in 67 consecutively admitted patients with bipolar illness. Thyroid hormone levels -- thyroxine (T4), free T4 and triiodothyronine (T3) -- were not significantly different in the 31 rapid cyclers (> or = 4 affective episodes/year) than in 36 non-rapid cyclers. Analysis of covariance indicated a non-significant trend relation between higher T4 and a greater number of affective episodes in the year prior to admission and male gender when age was covaried. Several previous reports, primarily in medicated subjects, have suggested a link between rapid cycling patients and decreased peripheral thyroid indices (low hormone levels and elevated TSH), but now the majority of studies do not support such a relation. Among those in the literature, this study includes patients studied for the longest time off medications and further suggests that the commonly-cited relation between subclinical hypothyroidism and rapid cycling bipolar illness be reevaluated.