A STUDY OF THE EFFECT OF RESERPINE ON THYROID SECRETION IN SEVERAL MAMMALIAN SPECIES

Abstract

SUMMARY Investigations were carried out to study the effect of reserpine in doses up to 100 μg./100 g. body weight on thyroid function as determined by thyroxine secretion rates (TSR) in the rat, hamster, guinea-pig and mouse. It was found that 20 μg. reserpine/100 g. body weight had no effect on TSR or on body weight. At higher doses (50–100 μg./100 g.) TSR was depressed, greater depression being noted with doses of 100 μg. Food intake was reduced at the higher dosage resulting in significant losses of body weight (up to 33%). In long-term studies in rats, administration of 10 μg. reserpine/100 g. body weight for 6 weeks had no effect on TSR. No dose of reserpine that would inhibit TSR without contributing to body weight loss and depression in food intake was found. Administration of reserpine in these low doses did not influence body temperature. Uniform results were obtained in all the species studied. It is concluded that reserpine, in low doses, has no influence on thyroid function as determined by the rate of thyroxine secretion. Higher doses of reserpine, however, inhibit thyroid secretion, but such an inhibition appears to be secondary to the effects of inanition brought about by a toxic action of the drug and/or its hypothalamic effects.