Assessment of functional activity of the bovine thyroid gland using morphometry and two markers of cellular proliferation

The aim of the study was to contribute to objectivity of morphological investigation of thyroid gland in cattle. Thyroid gland in euthyreoid cows is composed of conspicuously different size follicles. Using image analysis the follicles were classified in accordance to their diameter in three size categories: large (175.1-615 mum), medium, (80.1-175 mum) and small (15-80 mum). Moreover, there were considerable individually different proportions among the determined size categories of the follicles. Height of the follicular epithelium was in reverse relation to size of the follicles. Mean values were 7.06 mum. 8.04 mum and 8.39 mum, respectively. Proliferative activity of follicular epithelium. evaluated by means of proliferating nuclear antigen and nucleolar organizer regions was high in the small, moderate in the medium and low in the large follicles. We found these markers suitable for evaluation of proliferative activity of follicular cells in the bovine thyroid gland.