The biological action of substances related to thyroxine. 1. The effect of n-alkyl 3:5-diiodo-4-hydroxybenzoates on oxygen consumption in mice

Abstract

The methyl, ethyl, propyl, and butyl esters of 3: 5-diiodo-4-hydroxybenzoic acid exhibited a strong antithyroxine effect, the butyl compound being the most active. The activity was almost as great by mouth as by the subcutan. route. The higher esters were less potent, and the acid itself showed only weak activity. Variations in halogen substitution or elimination of the 4-hydroxyl group in the n-butyl ester completely abolished the thyroxine-inhibitory effect. n-Butyl 3: 5-diiodosalicylate showed slight antithyroxin activity. Nal was inactive. Evidence is presented in support of the view that a specific competitive inhibition of thyroxine is involved.