Histology and histochemistery of the thyroid gland in three post-hatching development Egyptian Baladi chickens (Gallus G. domesticus): Novel insights of thyroid hormone levels with special insights regarding bone formation.

The thyroid gland is an essential endocrine organ that regulates the body's metabolic rate, helps maintain the body's weight, and supports the development of various body organs. Our research is a novel effort to examine the histomorphometric features of the thyroid gland and its relationship with the bone formation of three post-hatching development age stages of Baladi chickens: juvenile (fourteen days old), immature (two months), and mature (six months). This study employs histology, histochemistry, and analysis of thyroid hormone levels. Thyroid glands and femurs of thirty male, healthy chickens of three different post-hatching development ages were collected. The results indicated that the thyroid gland of fourteen-day-old chicks primarily consisted of a single-layer capsule and small to medium inactive follicles. As the chickens aged, the capsule developed into two layers, and there was an increase in large and active follicles. In the thyroid gland at six months, the active follicles were lined with cuboidal cells featuring vacuolated cytoplasm. The colloid (hormonal secretion of follicles) showed a pale acidophilic reaction in younger birds, which deepened with age. Thyroid hormone levels increase with age as a result of heightened gland activity. The histological changes of the femur correlate closely with the development of the thyroid gland across different ages. Future research aimed at gaining a deeper understanding of the intricate histophysiology and histopathology of the digestive system in zoo birds would benefit from this knowledge.