Food deprivation decreases the blood TRH concentration in the rat

Adult male rats were deprived of food for 1-6 days and the hypothalamo-pituitary axis in these rats was evaluated. Food deprivation caused a progressive decrease in TRH concentration in the peripheral blood with a concomitant reduction in the blood TSH level. No significant change was observed in the hypothalamic, extrahypothalamic or pancreatic TRH concentration between the control and starved groups. Starvation did not cause a significant change in the pituitary TRH receptors or the in vitro responsiveness of TSH to TRH. These data imply that the reduction in the blood TRH level may contribute in part to the decrease in the blood TSH level after food deprivation, but the origin of the blood TRH has remained to be determined.