Activity of thyroid parafollicular (C) cells in rats with hyperthyroidism--preliminary ultrastructural investigations.

In the thyroid gland of mammals, except the basic follicular (F) cells, parafollicular (C) cells are detected. They belong to disperse neuroendocrine cells of the APUD system. Co-localisation of F and C cells in the thyroid gland is not accidental. It seems possible that there is an interaction between them, mediated by the peptidergic hormones. Calcitonin (CT) is proposed as an essential indicator of C cells. The role of C cells in the function of the thyroid gland has been not clarified till now, especially in hyperthyroid state. There are only a few data which document the ultrastructure of C cells in the physiological and pathological state. In the present study, the ultrastructure of thyroid C cells in an experimental model of hyperthyroidism was evaluated. Our preliminary study may confirm the functional interaction between follicular and parafollicular cells in the thyroid gland.