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THE EFFECT ON THE GROWTH RATE OF THYRO-PARATHY-ROIDECTOMY IN NEWBORN RATS AND OF THE SUBSEQUENT ADMINISTRATION OF THYROID, PARATHYROID AND ANTERIOR HYPOPHYSIS12
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Animal PhysiologyDevelopmental BiologyPhysiologySevere RetardationThyroid DiseaseParathyroid DiseaseParathyroid HormoneThyroid DisordersImmature AnimalsParathyroid GlandThyroid HormonePublic HealthEndocrinologyMedicineThyroid PhysiologySevere Growth RetardationReproductive Endocrinology
Athyroidism has long been known to result in severe retardation of growth, first seen clinically in cretins, later experimentally induced by thyroidectomy of immature animals. The work of von Eiselsberg (1) and Simpson (2, 3) on sheep and goats, and of Tatum (4) on rabbits indicated that, in younger animals the severity of the reaction to thyroidectomy is relatively greater than in older ones. Hammett (5, 6, 7), however, reported that in rats thyro-parathyroidectomized at ages between 23 and 100 days a more severe growth retardation occurred in the older than in the younger animals. Since age seems to be an important factor in the response to thyroid deficiency, newborn rats were subjected to thyro-parathyroidectomy (8). No previous reports have dealt with ablation in such young mammals. Rats are well adapted for these studies because they are very immature at birth, and the characteristic structure of the thyroid develops only during the last 3 days in utero (9).