Morphological and histometric parameters of the thyroid gland in slaughter cattle

The study presents an evaluation of morphological and histometric parameters of the thyroid gland of slaughtered cattle (29 cows, 10 bulls, 7 heifers and 4 calves). The thyroid gland of bulls contained 34.7% of large follicles while their content in cows and heifers was 32.6% and only 19.2%, respectively. The average follicle length was 162.0±19.8 ?m in bulls, 153.5±24.8 ?m in cows and 122.4±10.1 ?m in heifers. The highest thyreocytes were found in heifers and bulls (9.45±1.17 and 9.42±1.50 ?m, respectively) and the lowest in cows (8.46±2.13 ?m). A positive relationship was determined between the iodine content of the thyroid gland and the percentage of large follicles (r = 0.55) while the relationship between iodine content and thyreocyte height was negative (r = –0.21). In the thyroid gland of older cows medium and large follicles with low cubic to flat thyreocytes were dominant. Some follicles contained necrotic thyreocytes and the cytoplasm contained lipofuscin. The results suggest the influence of an increased iodine content in the thyroid gland on follicle size and thyreocyte height