[Circadian rhythm of temperature, heart rate and blood pressure in normal rats and hypothyroid rats].

We explored the circadian variation of core temperature, heart rate and blood pressure in hypothyroid and euthyroid male Sprague-Dawley rats. A circadian rhythm was quantified by the population mean-cosinor method for the core temperature of both hypothyroid and intact rats, whereas for the blood pressure and heart rate values a circadian rhythm was validated by rejection of the zero-amplitude assumption only in the hypothyroid rats. Whether hypothyroid rats adjust to new schedules at a rate different from euthyroid animals is an inference from these studies awaiting scrutiny.