Pick an ailment — joint pain, brain fog, insomnia — and there’s probably a peptide therapy promising to treat it. Never mind that many of these amino acid–based products are not approved by the U.S. Food and Drug Administration, have hardly been studied in people and may not be intended for human use at all. Some people aren’t afraid to go DIY, buying peptides from online retailers or overseas suppliers and injecting them at home, whether their doctors know about it or not.  There’s a clear solution for regulators dealing with an “illicit market” like the one emerging for peptides, says Mitch Zeller, a former FDA official who left the agency in 2022: “Step up your enforcement game” to stop its spread. His successors at the FDA, however, appear to be taking a different approach. Rather than reining in the health-hacking peptide craze, they appear poised to take steps that will fuel it. Health and Human Services Secretary Robert F.…