THE DURATION OF ACTION OF SINGLE DOSES OF THYROID HORMONE1

Abstract

REPORTS on the duration of action of thyroid compounds vary considerably. As early as1904, Magnus-Levy reported that the effects on the basal metabolic rate of thyroid feeding in myxedematous patients lasted 80 days. Kendall (1917), probably the first to inject pure thyroxin intoanimals, compared the effects of small daily doses and a single large dose. A goat receiving 9 mg.daily was dead at the end of 11 days; the single injection of 150 mg. in another goat produced changes in the electrocardiographic tracings which returned to normal in 2 or 3 days. In contrast to-these results, Kendall (1923) reported that a single dose of thyroxin in a myxedematous patient would exert its physiologic effect for 5 to 6 weeks. Boothby, Sandiford, Sandiford, and Slosse (1925) showed that the rate of decline of the basal metabolism following withdrawal of thyroid administration in myxedematous patients was a straight line, when plotted on semilogarithmic paper.