Effect of peptides Lys-Glu-Asp-Gly and Ala-Glu-Asp-Gly on the morphology of the thymus in hypophysectomized young and old birds

Experimental study conducted in collaboration with the Khavinson group, comparing two analogous tetrapeptides of the bioregulator family: Lys-Glu-Asp-Gly (KEDG, Testagen) — proposed as testicular active — and Ala-Glu-Asp-Gly (AEDG, Epitalon) — pineal-derived. The experimental model was hypophysectomized birds (young and old), a manipulation that produces dysfunction of multiple endocrine axes and atrophy of lymphoid organs such as the thymus.

The design was strictly comparative between the two tetrapeptides of the AEDG/KEDG family. Neonatal and adult hypophysectomy produced pronounced morphological alterations in the thymus, with loss of cortical and medullary architecture, thymocyte reduction, and oxidative stress. Administration of KEDG and AEDG peptides was tested in birds of different ages, with detailed histological evaluation of the thymus and quantification of lymphoid cells.

Results showed that both peptides promoted partial recovery of thymus morphological structure, regardless of bird age — suggesting a tissue-specific mechanism of action that does not require the intact pituitary axis. The authors observed that the anterior pituitary-derived peptide (AEDG) was more effective than the posterior pituitary-derived (KEDG) in thymic restoration, but both demonstrated detectable biological activity and dose-dependent direction.

This work is one of the few PubMed-indexed references that explicitly mentions KEDG (Testagen) in a peer-reviewed preclinical context. The literature on Testagen is notoriously sparse — only one clinical study published in a Ukrainian journal without full English text — and this article is one of the most solid scientific sources documenting biological activity of KEDG, albeit in an avian model and in a lymphoid organ context (not testicular). The scarcity of primary data on Testagen remains an important limitation: compared to other Khavinson bioregulators such as Epitalon or Vilon, the evidence base is significantly thinner, and findings here should be interpreted as preliminary signals.