Calcium metabolism in normal and thyro-parathyroidectomized goats

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Abstract
The effects of thyro-parathyroidectomy on Ca metabolism in the goat have been investigated using stable Ca balance techniques and the isotopes Ca45, Ca47 and Sr85. Thyro-parathyroidectomized goats, whether receiving Supplementary thyroxine or not, are in negative Ca balance, whereas normal or thyroidectomized animals are in positive balance. Gastro-intestinal absorption of Ca45 is iess in thyro-parathyroidectoraized goats, whether receiving supplementary thyroxine or not, than in either normal goats or thyroidec-tomized goats receiving thyroxine supplements. The rate of endogenous secretion of Ca into the gastro-inetstinal tract is unchanged by either thyroidectomy or thyro-parathyroidectomy. Urinary excretion of Ca is also apparently unchanged. The bone Ca accretion rate is reduced to approximately the same extent in thyroidectomized and thyro-parathyroidectomized goats. Thyroxine supplements restore the bone accretion rate of both groups of animals to normal or greater than normal levels. The bone Ca resolution rate is greater inthyro-parathyroidectomized goats, whether receiving thyroxine supplements or not, than in either normal goats or thyroidectomized goats receiving thyroxine supple me nts.