The effect of fasting on thyroidal T4-5'monodeiodinating activity in mice

Abstract

Complete fasting induces a significant decrease of serum T3 and a fall in TSH in rodents and man.

The Nuclear Receptor CAR Is a Regulator of Thyroid Hormone Metabolism during Caloric Restriction

“…T 3 and T 4 levels decreased by 39% (p Ͻ 0.005) and 36% (p Ͻ 0.05), respectively, after a 24-h fast in wild-type mice. The magnitude of these changes is consistent with previously published mouse studies (23). In contrast, the fasted Car Ϫ/Ϫ mice did not show statistically significant changes in either T 3 or T 4 .…”

Effects of Partial and Full Feed Restriction on the Plasma Levels of Thyroid Hormones and Testicular Activity in the Male Air-breathing Catfish, Clarias gariepinus during Different Phases of the Breeding Cycle

“…It, thus, seems that feeding status (partial or full feed restriction) affects the plasma levels of thyroid hormones in a phase-dependent manner. Fasting has also been reported to alter the activity of deiodinase enzymes in vertebrates (Shields and Eales, 1986;Wu, 1990;Diano et al, 1998;Van der Geyten et al, 1998) and so, the increase in the T 3 /T 4 ratio in the present study suggest increased deiodination in this fish during the full feed restriction period. Further, in vertebrates, fasting has been shown to down-regulate the hypothalamo-hypophyseal-thyroidal (HHT) axis which is assumed to represent an energy-saving mechanism in times of food shortage (van Haasteren et al, 1996;Boelen et al, 2008).…”

“…Fasting and refeeding have been reported to have marked effects on the thyroid activity, circulating levels of the thyroid hormones and their metabolism in different groups of vertebrates (Eales, 1988;Wu, 1990;Cokelaere et al, 1996;Van der Geyten et al, 1999;Wright, Proctor and Alves, 1999;Kohel et al, 2001;Ortiz et al, 2001;Reyns et al, 2002;Coppola et al, 2005). In fishes, food deprivation suppresses the plasma T 4 and T 3 levels, reduces thyroid tissue sensitivity to thyroid stimulating hormone (TSH), causes a reduction in 5'-monodeiodinase and eliminates the plasma thyroid hormone daily patterns (Eales et al, 1981;Flood and Eales, 1983;Shields and Eales, 1986;Cerda-Reverter et al, 1996;Power et al, 2000;Gaylord et al, 2001).…”

American Thyroid Association Guide to Investigating Thyroid Hormone Economy and Action in Rodent and Cell Models

“…In rats, fasting is associated with an approximately 50%-75% drop in serum T 4 and T 3 that takes place in the first 48 hours (356). In mice, the drop in serum T 3 is about 50% and takes place by 36 hours of fasting (357). Fasting also leads to a reduction in liver D1 and increase in D3 activities (358,359).…”