Exogenous Calcitonin Suppresses Growth Fraction of Thyroid C Cells

Abstract

Calcitonin (CT) is a peptide hormone synthesized and secreted by the parafollicular (C) cells of the thyroid. Little is known about the mechanisms controlling proliferation of C cells by other humoral factors including CT, and there is no report that CT suppresses C cell proliferation. The effects of short-term administration of CT on C cell growth fraction were analyzed using BrdU and CT double immunohistochemical method in the rat thyroid. Continuous administration of 0.4 IU/kg and 40 IU/kg synthetic salmon CT for 14 days induced dosedependent suppression of BrdU labeling number of C cells without decrease of C cell to the total thyroid follicular cell ratio. These results suggest that exogenous CT may induce negative feedback to C cell proliferation in the thyroid.

Response of trabecular bone, thyroid C and follicular cells to synthetic salmon calcitonin in middle‐aged orchidectomized male rats

“…In this study, we demonstrated that treatment of Orx rats with salmon CT further decreased the already reduced Vc and Vvc of thyroid C-cells, whereas serum CT was elevated due to Orx. This inhibitory effect of exogenous CT on rat thyroid C-cell function and proliferation was described earlier (Morimoto et al 1984;Mori et al 2003). Exogenous CT suppresses C-cell function probably by involving a negative feedback mechanism.…”

“…The mRNA for CT receptors has been shown to be expressed in both tissue and cell lines of human medullary thyroid carcinoma (Frendo et al 1998a, b). Therefore, CT may act directly via its own receptors on C-cells (Mori et al 2003). Under our experimental conditions, CT treatment also affected the overall structure of rat thyroid glands.…”

“…; Mori et al. ). Exogenous CT suppresses C‐cell function probably by involving a negative feedback mechanism.…”

“…Therefore, CT may act directly via its own receptors on C‐cells (Mori et al. ). Under our experimental conditions, CT treatment also affected the overall structure of rat thyroid glands.…”

Localization of Calcitonin Receptor mRNA in Rat Kidney: an In Situ Hybridization Study

“…CT down-regulates serum levels of calcium, by suppressing bone resorption and calcium excretion from the kidney [5,10,18]. On the other hand, excessive CT induces negative feedback to C cell proliferation [15]. These direct and specific actions of CT on thyroid, bone and kidney have been confirmed by the presence of specific calcitonin receptors (CTR).…”