Histological and histometrical changes of ostrich thyroid gland during summer and winter seasons in Tehran, Iran
The seasonal changes of ostrich thyroid structure in Tehran, which has a hot summer and a relatively cold winter, were studied. The study was conducted on thyroid glands of 20 ostriches in two groups (summer and winter group). The samples were collected by autopsy with a maximum of 0.5 cm thickness and were fixed in 10% formalin saline. The samples were embedded in paraffin, sectioned at 5 to 6 μm, stained by Hematoxylin and Eosin method and examined under light microscope. The results showed that the seasons had a significant effect on thyroid parenchyma-stroma ratio. This ratio was significantly increased in winter. The number and diameter of thyroid follicles were increased in winter too. The histometrical results showed that the number of thyroid follicles, active follicles and follicles with vacuolated colloid were significantly increased in winter (p < 0.01). The diameters of large follicles and epithelium height of follicles were also increased in winter significantly (p < 0.01). However, the results showed that the parenchyma of thyroid glands was significantly increased in winter which is associated with increase in thyroid activity in winter.
Key words: Seasonal changes, histology, thyroid, Ostrich, Iran.