Influence of thyroidectomy and compensatory treatment with L-thyroxine upon tissue glycogen stores during last part of pregnancy in the rat

Abstract

Female rats on 15th day post coitum or during pro-oestrous phase of the oestrous cycle were thyroidectomized and their glycogen contents in the uterus, heart and liver were determined. Thyroidectomy produced 50 % decline in pro-oestrous heart but similar treatment resulted in 51 % increase in the heart of pregnant females. Hepatic glycogen reserves in the pregnant females declined by 29 % from non-operated value after thyroidectomy. Uterine glycogen stores declined in cyclic females after thyroidectomy when the results were compared with normal values (30 % lower). The pregnant females responded completely in a different manner for uterine glycogen since marked increase of 34 % was observed after thyroidectomy on 15 day post coitum. Pretreatment with L-thyroxine to operated animals did not produce any significant difference for cardiac and uterine glycogen of cyclic animals but hepatic reserves were modified to the normal value. Administration of L-thyroxine to thyroidectomized rats during pregnancy increased glycogen reserves of all the three organs studied and the mean values became markedly higher than the operated as well as non-operated values. The results provide evidence that thyroid hormones have an important influence on the regulation of energy reserves in the body during pregnancy and the effects are different between cyclic and pregnant females.