Testagen peptide: what the Khavinson tetrapeptide is, what the bird studies show and what is unknown

Testagen is the trade name for the tetrapeptide Lys-Glu-Asp-Gly: lysine, glutamic acid, aspartic acid and glycine in that order, written KEDG in single-letter code, so the KEDG peptide and testagen are the same thing. A 2025 chemistry paper that used it as a copper corrosion inhibitor spells the full structure out as H-Lys-Glu-Asp-Gly-OH, meaning a free amino group at one end and a free carboxylic acid at the other ^[10]. It is one of the short peptides designed by Vladimir Khavinson’s group at the St Petersburg Institute of Bioregulation and Gerontology, and it shares its last three residues with epitalon, which is Ala-Glu-Asp-Gly; the only difference is lysine in place of alanine at the first position.

The name suggests the testis, and research suppliers describe the testagen bioregulator as a testicular or male reproductive peptide. That is not how the published literature describes it. In every PubMed-indexed study of KEDG, the peptide is said to have been synthesised on the basis of the amino acid composition of peptide complexes from the anterior lobe of the pituitary gland, with Ala-Glu-Asp-Gly assigned to the posterior lobe ^{[1] [3] [5]}. We could find no paper that designs, tests or even mentions testagen in relation to testicular tissue, testosterone or sperm. Readers should treat the testis label as a seller’s description rather than a finding.

As with the rest of the Khavinson peptides, almost all of the evidence comes from one network of Russian laboratories, chiefly Boris Kuznik’s group in Chita, and was published either in the Bulletin of Experimental Biology and Medicine, a translated Russian journal indexed in PubMed, or in Russian-language journals with English abstracts. The one independent paper on KEDG is about metal corrosion, not biology ^[10].

The developers’ general theory is that short peptides enter cells, reach the nucleus and change gene expression by binding DNA or histones in a sequence-dependent way. Testagen was one of the peptides used to test this. In 2011, fluorescently labelled testagen, epitalon and pinealon were all seen in the cytoplasm, nucleus and nucleolus of HeLa cells after incubation, and in test-tube experiments each peptide quenched the fluorescence of labelled DNA fragments differently; testagen, epitalon and pinealon appeared to prefer sequences containing CAG, while bronchogen preferred CTG ^[6]. A 2013 follow-up reported that Lys-Glu-Asp-Gly and five other short peptides bound labelled wheat histones H1, H2B, H3 and H4, apparently at their N-terminal tails, and that binding depended on the peptide, the histone and the methylation state of the DNA ^[7].

The group’s 2020 review of peptide effects on cell differentiation lists KEDG among peptides that stimulate the differentiation of immune cells, alongside KE (vilon), KED (vesugen) and others ^[8]. A 2023 modelling study found that KEDG and KEDP (prostamax) were among the short peptides with the highest predicted binding to the intestinal transporters LAT1, LAT2 and PEPT1, which the authors proposed as the route by which such peptides could be absorbed after oral dosing ^[9].

None of this identifies a receptor or a pathway specific to testagen, and none of it involves the testis. The fluorescence and docking work shows that a small, charged tetrapeptide can associate with DNA and histones in a test tube; it does not show that it does so at meaningful concentrations in a living animal, or that any observed effect in birds follows from it.

Every animal study of testagen used the same unusual model: chickens whose pituitary gland had been surgically removed, either as newborns or later in life, which produces secondary hypothyroidism, immune suppression and clotting abnormalities. In 2008, Kuznik and colleagues reported that giving Lys-Glu-Asp-Gly or Ala-Glu-Asp-Gly to neonatally hypophysectomised chickens for 40 days raised thyroid-stimulating hormone and thyroid hormone levels and restored the structure of the thyroid gland ^[1]. A 2010 paper in the same model described enlarged follicles, colloid build-up and flattened epithelium in the thyroid after hypophysectomy, together with depressed immunity, hypercoagulation and reduced fibrinolysis, and reported that the pituitary peptides prevented the thyroid atrophy and normalised immune and clotting measures; the changes, and the peptide effects, were smaller when the operation was done in one-year-old birds ^[2].

Two 2011 papers extended the work to old hens. Forty days of either tetrapeptide significantly reduced the hormonal and structural thyroid changes after hypophysectomy, but the normalising effect on TSH and thyroid hormones was weaker in old birds than in chicks ^{[3] [4]}. In 2013 the same group looked at the thymus and found that both peptides promoted recovery of thymic structure in hypophysectomised birds of any age, with the anterior pituitary peptide (testagen) having the stronger effect ^[5].

That is the whole of the animal evidence: thyroid and thymus recovery in birds lacking a pituitary, published by one group. There are no rodent studies, no studies in intact animals, and no measurement of testosterone, LH, FSH, sperm or testicular tissue in any species. Claims about testagen and testosterone, libido, fertility or muscle have no published study behind them. If a seller cites one, ask for the reference; we could not find it.

The related peptide epitalon, which differs from testagen by one amino acid, has a much larger literature including reports of restored reproductive function in old rats, but those results belong to epitalon and cannot be transferred to testagen. The two peptides were tested side by side in the bird studies and behaved similarly, which is consistent with the shared Glu-Asp-Gly core doing most of the work ^{[1] [5]}.

We found no human study of testagen of any kind, controlled or uncontrolled, in PubMed. There is no entry for Lys-Glu-Asp-Gly on ClinicalTrials.gov. A search for the name returns one trial, but it is for an unrelated product: Testagen TDS is a brand of transdermal testosterone system being developed in the US, and its registered study is a skin-transfer study of that testosterone gel, not of the peptide ^[12]. The identical name is a source of confusion; a page about testagen testosterone results is likely to be about the gel.

This puts testagen at the bottom of the Khavinson series for human evidence. Pancragen and vesugen at least have small Russian clinical reports; testagen has none. Anyone using it is relying entirely on extrapolation from hypophysectomised chickens.

There is no human time-course. In the bird studies, the peptides were given for 40 days and outcomes were measured at the end of that course ^{[1] [3]}. Nothing is known about onset, duration or whether any effect persists after stopping.

The English abstracts of the bird studies state the duration of dosing, 40 days, but not the dose or route ^{[1] [2] [3]}. In related work by the same group, short peptides were typically given to birds and rodents by injection at microgram amounts per animal, but we cannot confirm the figure for testagen from the abstracts and will not guess. No human dose exists, and none is recommended here.

Research suppliers sell testagen as a lyophilised powder, commonly in 10 or 20 mg vials, and Russian supplement versions are sold as capsules. Neither amount comes from a dose-finding study. If you need to convert vial contents to a concentration for a laboratory protocol, use the peptide calculator or the testagen calculator page.

The bird studies administered the peptides by injection ^[2]. The developers’ transporter modelling proposes that KEDG could be absorbed from the gut via LAT and PEPT transporters ^[9], but no pharmacokinetic study has measured testagen in the blood of any animal or person after any route. The corrosion study confirms only that the peptide is stable and adsorbs to copper in salt water, which says nothing about its fate in a body ^[10].

At about 447 g/mol, testagen is close in mass to epitalon (about 390 g/mol) and to the other KED-family tetrapeptides, so a certificate of analysis should report the measured mass to within a dalton or so. A vial sold as testagen that shows a mass of 390 is epitalon, and one showing 461 or 488 is livagen or prostamax.

No safety study of testagen has been published in any species, and there is no human safety data at all. The bird studies do not report adverse effects, but they were not designed to look for them and did not include intact control animals given the peptide ^{[1] [2]}. The questions people ask, whether testagen raises testosterone, affects the prostate, causes acne or hair loss, or interacts with hormone therapy, cannot be answered because the relevant measurements have never been made.

Two things follow from the published mechanism. First, if the peptide genuinely raises TSH and thyroid hormone in animals lacking a pituitary ^{[1] [3]}, its effect in a person with an intact thyroid axis is unknown and could in principle be different or absent. Second, a peptide that binds DNA and histones in a test tube ^{[6] [7]} and is credited by its developers with stimulating immune cell differentiation ^[8] is, on their own account, biologically active in the nucleus; whether that is benign over long-term use has not been examined. Testagen is not on the FDA’s compounding list of substances that may present significant safety risks, unlike epitalon, which was nominated and later withdrawn ^[13]; absence from the list means nobody nominated it, not that it was reviewed.

Testagen is not an approved medicine in the UK, US, EU, Canada or Australia. Marketing it for human use with claims about testosterone or reproductive health would bring it under medicines law in the UK regardless of a research-use label, and the MHRA has licensed no such product. In the US it is not an FDA-approved drug and has not been on the compounding category 2 list ^[13]. In Russia it is sold as a dietary supplement, which confers no status elsewhere. The US trademark Testagen for a testosterone gel is unrelated to the peptide ^[12]. We have not confirmed its standing under the WADA Prohibited List, but any product actually containing testosterone would be prohibited.

For the rules on buying and holding research peptides in your country, see the legal status overview, the UK page, the US page and the Australia page.

Testagen is supplied as a freeze-dried powder. It contains no cysteine, methionine or tryptophan and should be reasonably stable, but the general rules apply: keep the sealed vial cold, dry and away from light, refrigerate any reconstituted solution and use it within a limited period. See how to store peptides and the bacteriostatic water guide.

Testagen is a four-amino-acid peptide and costs little to make, so a high price per milligram signals nothing about quality. Compare testagen prices across the stores we track, including UK listings and US listings. Read how to read a peptide COA before buying: because testagen differs from epitalon by a single residue and both are cheap, mislabelling between them is plausible, and only mass spectrometry, not HPLC purity, will tell them apart. Our third-party tested suppliers list shows which stores publish independent tests, and the third-party testing guide explains what those tests do and do not prove.

Sellers often sell a testagen epitalon stack, or pair it with pinealon or thymalin, or place it next to kisspeptin-10 and gonadorelin as a male hormone peptide. Those two peptides have real human endocrine data; testagen does not. For an overview of what research-use labelling means, see what research peptides are and how to spot a fake peptide supplier.