The Rates of Utilization of Thyroxine

These observations were made in an effort to determine the rate of production of thyroxine in normal man. Boothby, Sandiford, Sandiford and Slosse (1925) have shown that when thyroxine is injected intravenously at intervals of from two to fourteen days, the average daily dose required to maintain the basal metabolism of a " thyroidless " individual at the normal level is 0.25 mgm. Since the injections were not given daily, the possibility remained that some of the thyroxine administered may have been excreted unused. We have accordingly determined the minimum amount of thyroxine which must be injected intravenously or subcutaneously every day in order to accomplish the same result.