The Effect of the Active Thyroid Substance on Metabolism and Other Functions in Guinea Pigs

Abstract

Summary.Different preparations of dried thyroid from normal mammals and human beings and from cases of simple goitre have the same metabolic effect when given by mouth in equivalent daily doses based on the iodine content to mature male guinea pigs, accustomed to the metabolism determinations under standard conditions, while in exophthalmic goitre the iodine of the gland becomes less active.A partly purified product, elityran, also shows the same effect, while pure thyroxin, even when given subcutaneously is definitely less active. No difference was observed between the activities of thyroxin when given by mouth or subcutaneously.The metabolic effect of α‐dinitrophenol given by mouth reaches a maximum in about an hour and falls again rapidly while that of thyroid preparations takes two days to develop and by administration each day reaches a more or less constant level, maintained throughout the period of administration.Administration of iodine or di‐iodotyrosine reduces the metabolism raised by every day injections of thyreo‐stimulating hormone (artificial “Basedow”) and causes a regression of the histological and cytological “Basedow” symptoms in the thyroid gland, but has no effect on the hyperthyroidism brought about by feeding thyroid preparations.Refractoriness to the thyreo‐stimulating hormone was not observed in our case.The quantitative relation between dose and metabolic effect of dried thyroid preparations was studied on 44 animals. On 9 of these no well defined metabolic level could be obtained. The 35 animals showed a fairly regular relationship. The average resting metabolism of the guinea pigs was 100.1 ± 3.4 ml O2/m2/min. The increases were for 0.15 mg J/m2/day 17 ml O2/m2/min., for 0.25–29.0, 0.50–35.7 and 10.00–50.4. This corresponds to an approximately straight line relation between log dose and the absolute rise in metabolism.