Supernumerary parathyroid structures in the neck and thymus of parathyroidectomized rats and their relationship to recovery from hypocalcaemia.

Parathyroidectomized Hooded Lister rats were examined for the presence of supernumerary parathyroid structures in the thyroid and ectopic parathyroid tissue in the thymus. Thirty per cent of the animals showed supernumerary tissue in their necks and maintained a significantly higher post-operative serum calcium. Sixty-five per cent possessed ectopic thymic parathyroid tissue. Parathyroidectomy seemed to provide a stimulus for ectopic parathyroid tissue in the thymus, although this tissue did not significantly improve the serum calcium post-operatively. The implication of ectopic parathyroid tissue in metabolic studies on parathyroidectomized rats is discussed.