[Parafollicular cells in the regenerating thyroid gland].

Ten days after partial thyroidectomy (excision of the lower half of the thyroid left lobe) made in mature male rabbits, functional activity of thyrocytes markedly rose. That was the organism compensatory reaction to the decreased thyroid hormone production due to the enhancement of the pituitary thyrotropin secretion. However, parafollicular cells detected by the Sawicki method underwent reduction in the number and size, which was fairly appreciable in the regenerating thyroid lobe and insignificant in the lobe left intact. This reduction is probably caused by the fact that secretory activity of parafollicular cells is stimulated by sympathetic impulses, whereas in the regenerating thyroid, there prevail the parasympathetic effects.