Effects of starvation on circadian variations of plasma TSH in rats

Abstract
Diurnal fluctuations of plasma TSH were investigated in ad libitum fed rats as well as after a 3 day starvation period in order to study the relationship between the circadian pattern of TSH secretion and nutritional status. The persistence of a circadian TSH rhythm after a 3 day starvation without any change in the amplitude of plasma TSH variations was shown. The 24 h average plasma TSH levels were significantly lower. A suggestive acrophase occurred at the same period of the day in starved and fed rats. Apparently the control of plasma TSH concentrations and nycthemeral rhythm are not closely related and may even possibly be independent of one another.