Influencers, celebrities and everyday people are raving about the injectable substances, which promise everything from youthful skin to speedy muscle recovery. The unapproved drugs, often manufactured in China, are driving a gray-market craze. Now, they have an ally in Health and Human Services Secretary Robert F. Kennedy Jr., who wants to make peptides easier—and legal—to buy.

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Indiana officials are barring Piece by Piece Autism Centers from billing the state’s Medicaid program two weeks after the company’s practices were detailed in a WSJ article, state officials said.

The ideal number of close friends varies from person to person—and by gender—and changes as we move through different phases of life, writes Clare Ansberry.

Scientists successfully unfroze part of a mouse brain—and it still worked. Researchers revived the frozen tissue in a way that preserved its functionality, which could be helpful for testing drugs, examining diseases, or, someday, preserving entire organs or bodies.

Merck reached a nearly $6 billion deal for cancer biotech company Terns and its promising leukemia treatment. If it proves to work safely, the drug would give Merck a boost as it prepares for its top-selling drug, Keytruda, to lose patent protection.

Pfizer’s Lyme vaccine missed the mark in a study, complicating its quest for approval. The shot was more than 70% effective at preventing the disease in the trial, but not enough people contracted Lyme for the findings to be conclusive. Pfizer is pushing ahead anyway.

The share of new jobs in the last two years that were healthcare roles, according to an analysis of Bureau of Labor Statistics data. Over the past year, the U.S. has added 156,000 jobs—but healthcare alone was responsible for 375,000 new jobs. Strip out the medical sector, and the rest of the American economy is actually losing jobs.

• Would you use cadaver fat for a boob job or butt lift? Some people already do. (The Guardian)

• Here’s what an expert on the gut microbiome eats in a day. (The Washington Post)

• MDMA therapy in Australia is showing results, but the cost is limiting access. (The New York Times)

The Health newsletter is your weekly guide to all the news that affects your health and well-being. This edition was curated and edited by Conor Grant—send him feedback or questions at conor.grant@wsj.com (if you’re reading this in your inbox, you can just hit reply). Got a tip for us? Here’s how to submit.