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July 31, 1948

Current Comment

JAMA. 1948;137(14):1229-1230. doi:10.1001/jama.1948.02890480049014

METABOLIC FATE OF THYROXIN  The development of highly sensitive technics for the estimation of radioactive isotopes has made possible the study of the metabolic fate of active drugs such as thyroxin. When this hormone, labeled with radioactive iodine, is injected into rats, more than 50 per cent of the administered dose may be recovered after two hours in the gastrointestinal tract, liver and pancreas, mainly inunaltered form.1 Two days after the injection, about 80 per cent may be recovered from the feces, largely unchanged, while some 11 per cent is present as inorganic iodide in the urine. The liver, kidneys, adrenals, ovaries and lymphatic organs tend to maintain their radioactivity at this time. The thyroxin appears to enter the intestinal tract by way of the liver, the organ active in the excretion of certain other halogenated compounds. The results are interesting especially because they form a possible experimental basis