Effect of Prolonged Thyroid Administration on Aged Male Rats

Abstract

THE second phase of an earlier study has been completed and it was felt that a brief note of the results would complement the first report¹. Male Holtzman strain rats (400 gm.) were given orally purified thyroid extract (‘Proloid’, Warner-Chilcott) from 12 months of age until death at 21 months in three daily dosage series: A, B, and C, equivalent to 15, 60, and 240 mgm. respectively for a 70 kgm. human. At necropsy, all the principal organs (the same as those examined in the first phase¹) after gross examination were fixed in buffered 10 per cent formalin, paraffin processed, and stained in the usual way and histochemically for elastic, collagenic, and reticular tissues and for neutral and acid polysaccharides, as in the first series of experiments^2–4. Sections were compared with each other, with those of untreated control animals of equal age, and with sections obtained from rats with hypothyroidism induced by iodine-131. Organs from 84 experimental animals were studied with special regard to the vascular structures and the connective and epithelial tissues.