Triiodothyronine turnover in hospitalized psychogeriatric patients.

In a group of 12 hospitalized psychogeriatric patients, the fractional triiodothyronine (T3) turnover rate was significantly higher than in healthy control subjects of the same age, whereas the thyroxine (T4) turnover rate and other aspects of pituitary-thyroid function were virtually similar in both groups. Despite the presence of manifestations of sympathetic overactivity or hypermetabolism, the patients did not have true hyperthyroidism, as verified by the laboratory findings and the results of antithyroid treatment. The increases T3 turnover in aged hospitalized patients with brain disorders may be a compensatory mechanism which develops under these particular circumstances in order to maintain neurohormonal homeostasis. An alternate possibility is that the increased T3 turnover is secondary to hyperkinesis.