Changes in Small Round Follicles of the Thyroid Gland During Postnatal Ontogenesis of Hissar Sheep in Different Natural Regions

The dynamics of changes in the morphometric parameters of the histological structures of the thyroid glands in sheep raised under natural conditions with varying degrees of iodine deficiency were studied during postnatal ontogenesis. In Hissar sheep raised in the Kashkadarya region, a rapid increase in the absolute diameter of small round follicles of the right lobe of the thyroid gland was observed from 3 days to 3 months of postnatal development, followed by a gradual decrease from 18 to 60 months of age. In Hissar sheep raised in the Fergana region, the absolute diameter of small round follicles showed a rapid increase from 3 days to 12 months of postnatal ontogenesis, reached its maximum at 24 months, and then significantly decreased by 60 months of age.