Effects of Peptides Lys-Glu-Asp-Gly and Ala-Glu-Asp-Gly on Hormonal Activity and Structure of the Thyroid Gland in Hypophysectomized Young Chickens and Old Hens

Hypophysectomy in 5-days chickens and old hens was followed by hormonal disturbances and structural changes in the thyroid gland. Administration of peptides Lys-Glu-Asp-Gly and Ala-Glu-Asp-Gly synthesized on the basis the amino acid composition of extracts from the anterior and posterior lobes of the pituitary gland, respectively, to hypophysectomized birds for 40 days significantly reduced the degree of these changes. The normalizing effect of synthetic peptides on the concentration of thyrotrophic hormone and thyroid hormones in old hens was less pronounced than in chickens.