Hyperthyroxinemia in patients with acute psychiatric disorders.

Thyroid function tests were measured in 645 patients admitted to an acute psychiatric disorders unit. Thirty-three percent had elevated serum thyroxine (T4), and 18 percent had an elevated free T4 index (FTI). Serum triiodothyronine (T3) was low, normal, or minimally elevated in 77 patients, with a high initial free T4 index. Twenty-two patients with an initial elevation of their free T4 index were serially followed (study group). Serum T4, free T4 index, and free T4 fell in every patient: serum T4 from 13.95 +/- 1.93 micrograms/dl (mean +/- standard deviation: SD) to 9.33 +/- 2.4 micrograms/dl (p less than 0.001); free T4 index, from 6.15 +/- 0.83 to 3.79 +/- 1.1 (p less than 0.001); free T4, from 2.43 +/- 0.65 mg/dl to 1.38 +/- 0.35 ng/dl (p less than 0.001). Serum T3 was initially normal or low, and then fell in 17 patients, and rose in five. Serial testing of thyrotropin-releasing hormone (TRH) demonstrated both flat and normal responses in patients with a variety of psychiatric diagnoses and at varying stages of thyroid disease activity.