Polysomnographic effects of thyroid hormones primary myxedema.

Nine primary myxedematous patients were subjected to all-night polysomnographic recordings under the following conditions: (1) basal or myxedematous state; (2) acute replacement therapy (treatment with thyroid hormones at doses that increased weekly to the maximal replacement dose, Mrd); and (3) chronic replacement therapy (maintenance on the Mrd; euthyroid state). The most striking abnormality found in the sleep pattern during the myxedematous state was observed in both young adult (greater than 20 years old) and adult (greater than 50 years old) patients, consisting of either a complete absence or very low levels of slow wave sleep (SWS). Replacement therapy was accompanied by a restoration of the normal sleep pattern in 3 of the 4 patients that were followed. In contrast, younger patients (14-18 years old with a bone age of less than or equal to 10 years) had normal levels of SWS, with the exception of an adolescent with a bone age of less than 3 years. The latency for rapid eye movement (REM) sleep tended to increase during acute replacement therapy and became normal when euthyroidism was reached. These results lend support to the proposal that thyroid hormones exert central effects on the adult CNS.