Preliminary immunohistochemical investigations of thyroid C cells in an experimental model of hyperthyroidism.

The role of the parafollicular (C) cells, the second most important cells in the thyroid gland, has not hitherto been clarified. They are considered to be disperse neuroendocrine cells of the APUD system and synthesise and release many of the regulatory peptides. Few publications are concerned with the evaluation of the structure and function of C cells in the thyroid gland or the probable relationship between these cells and the follicular cells in physiological and pathological conditions. For this reason immunohistochemical investigations were carried out into the activity of the C cells in rats in an experimental model of hyperthyroidism caused by chronic thyroxine influence. This C-cell activity was then evaluated. Differences in the quantity, distribution and calcitonin immunoreactivity of C cells were observed in hyperthyroid rats in comparison to the control group, together with a significant diminution of plasma TSH and calcitonin levels. Our preliminary study may indicate a functional interaction between follicular and parafollicular cells in the thyroid gland.

An immunohistochemical study of the thyroid parafollicular (C) cells in rats treated with cannabinoids - preliminary investigations.

The purpose of the present study was to evaluate the effect of a single intraperitoneal injection of a stable analogue of endogenous cannabinoid anandamide - R-(+)-methanandamide (2.5 mg/kg) and CP 55,940 (0.25 mg/kg), an egzogenous CB1 receptor-agonist, on the calcitonin (CT) immunoreactivity of the thyroid parafollicular (C) cells. Four hours after injection with both cannabinoids CT immunoreactivity, evaluated with an avidin-biotin peroxidase complex method by means of rabbit antibodies against CT, was seen to be enhanced in the parafollicular cells in comparison to those of the control group. In thyroids taken from cannabinoid-treated rats the majority of follicles, particularly those located peripherally were large in size, and had low epithelium. Moreover, dilatation of the blood vessels was observed. These changes were accompanied by a significant decrease in CT plasma level, without changes in calcium concentrations. This is the first evidence that a single injection of the cannabinoids R-(+)-methanandamide and CP 55,940 significantly decreases the activity of thyroid C cells.

Activity of the thyroid parafollicular (C) cells in simple and hyperactive nodular goitre treated surgically - preliminary investigations.

The aim of this study was to evaluate the significance of measuring calcitonin (CT) plasma concentrations in patients with simple and hyperthyroid goitre treated surgically. Eighty four patients who underwent operations during the years 2000-2002 were analysed. Plasma concentrations of CT were determined by commercially available radioimmunoassay on the day of hospitalisation. Elevated concentrations of CT were found in 8 patients: in 5 out of 26 (19.2%) and in 3 out of 33 (9.0%) patients with Graves' disease and with multinodular goitre, respectively. No major differences in concentrations of CT were observed in patients with simple goitre. Postoperative morphological analysis of pathologically changed hyperactive thyroids showed the presence of enlarged C cells distributed either in small groups or even singly with weakening immunohistochemical reaction for CT. These observations may point to the possibility of a relationship between the functional state of the thyroid gland and the activity of C cells.