Short-term severe thyroid hormone deficiency does not influence sleep parameters

The influence of short-term severe thyroid hormone deficiency on sleep is currently still unknown. Several studies have demonstrated an effect of long-term hypothyroidism on sleep disorders due to anatomical changes of the pharynx or body mass. The aim of this preliminary study, however, is to evaluate the changes in sleep patterns of patients with short-term hypothyroidism to elucidate the isolated effect of thyroid hormone withdrawal before anatomical changes can potentially occur.

Ten patients with differentiated thyroid carcinoma were enrolled in this study. Two patients discontinued the study and one patient was finally excluded due to obesity, so that the datasets of seven patients were available for study analysis. During the course of carcinoma treatment, each patient had previously undergone total thyroidectomy and I-131 remnant ablation. Polysomnographic measurements were performed twice: (1) over the course of two consecutive nights during severe thyroid hormone deficiency after levothyroxine withdrawal and prior to further diagnostics and therapy and (2) during euthyroidism after substitution with levothyroxine.

Comparison of the Epworth Sleepiness Scale during hypo- and euthyroidism for each patient revealed no statistically significant difference. Furthermore, the comparison of polysomnographic parameters like (1) apnea-hypopnea index, (2) the duration of various sleep stages, (3) duration of rapid eye movement sleep, (4) latency until rapid eye movement sleep, (5) total sleep time, (6) periodic leg movements, and (7) arousal index showed no statistically significant differences between the hypothyroid or euthyroid state.

We conclude that, in this preliminary experimental setting, short-term severe thyroid hormone deficiency per se does not cause sleep disturbances and a feeling of fatigue as described in other studies may be due to changes in perception or brain metabolism during hypothyroidism.