Sleep organization in hypo- and hyperthyroid rats

The relationship between thyroid hormones and mammalian sleep organization was studied in control, hypothyroid (with and without replacement therapy) and thyroxine-injected adult male rats. The results show an increased number of awakenings during slow wave sleep (SWS) in hypothyroid animals, whereas total sleep time, levels of SWS, paradoxical sleep, and diurnal organization were unaffected by thyroid status. Our findings indicate that adequate levels of thyroid hormone are necessary to sustain extended periods of SWS in the adult rat while hyperthyroid animals show no disruption of sleep organization. A corollary finding is that daily sleep quotas are independent of whole body metabolic rates.