Science

GHK-Cu has one of the longest research histories of any compound in this newsletter's coverage — discovered in 1973, and still being actively studied today.

We sent identical split samples from four commercial peptide batches to three accredited third-party labs. The purity figures that came back weren't identical — and the reasons why say more about the state of the industry than any single number could.

The five fields worth checking before the purity number — and what each one is actually telling you.

How retatrutide's three-receptor mechanism differs from the first wave of GLP-1 compounds, in plain terms.

We asked a working microbiology lab technician to walk us through what happens between “sample received” and a final sterility result — and why that gap is longer than most buyers expect.

A close read of the preclinical literature behind one of the most talked-about peptides in the community — and an honest accounting of the gap between animal models and everything else.

Three compound generations, three different receptor strategies. A plain-terms map of what separates them.

Two compounds, two different mechanisms, one shared target. The pharmacology behind the industry's most common pairing.

The cellular biology behind NAD+ is genuinely well-established. The leap from there to anti-aging claims is doing more work than most marketing admits.

A three-amino-acid fragment with an outsized research footprint. What KPV is, and what the inflammation research actually says.

Our most-read story of last year explains the origin of this publication's entire testing methodology — and why we stopped taking certificates at face value.

Two Russian-developed peptides with decades of domestic clinical use and a much thinner footprint in Western research literature.