The action of thyroid hormones at the cell level

Abstract

A number of conflicting mechanisms have been proposed in recent years to explain one or more of the multiple biological actions of thyroid hormones, such as the stimulation of growth, acceleration of metamorphosis, the regulation of basal metabolic rate and effects on protein, lipid and electrolyte metabolism (see Although there is no evidence to show that the effect on basal metabolic rate is more fundamental than are the other actions of the hormones, the majority of the mechanisms proposed attempt to explain the calorigenic action of thyroid hormones, especially since the discovery that administration of large doses of thyroxine or direct addition in vitro leads to uncoupling of oxidative phosphoryl- ation in liver mitochondria (Lardy & Feldott, 1951; Martius & Hess, 1951; Niemeyer, Crane, Kennedy & Lipmann, 1951). Other studies have also indi- cated some form of direct action of thyroid hor- mones on mitochondria or mitochondrial perme- ability as seen by swelling and contraction (Tapley,