Thyroid Function in the Young Pig and Its Relationship with Vitamin A

Abstract

Jungherr et al. ('50) observed hyperplasia of the thyroid glands in vitamin A-deficient bull calves. Johnson and Baumann ( '47) found that hyperthyroidism in the rat increased the liver storage of vitamin A. This work indicated that the outcome was not due to changes in the basal metabolic rate (BMR) per se, but was brought about by some other phys iological action of the thyroid gland. In spite of the fact that elevated BMR increased the rate of depletion of the liver vitamin A in the rat, thyroxine so enhanced the storage of vitamin A from the diet that liver concentration rose above that of controls (Johnson and Baumann, '48). Nevertheless, their study showed that changes in growth rate have a greater influence upon vitamin A utilization than changes in meta bolic rate. Wiese et al. ('48) suggested that, although rats rendered hypothyroid by thiouracil consumed their liver vitamin A at a lower rate, this was a consequence of their lower rate of growth. This was corroborated by work with dogs (Arnrich, '55) which further demonstrated that the hypothyroid con