Is Peptide YY legal in the United States?

A gut hormone released after meals alongside GLP-1. Infused into 12 lean and 12 obese people it cut buffet intake by about 30 percent in both, but the rodent finding it was built on failed a published multi-laboratory replication, and nausea kept it from becoming a drug.

Peptide YY is a 36 amino acid hormone released from the same intestinal L cells that release GLP-1 and oxyntomodulin, in proportion to the calories in a meal. The enzyme DPP-4 clips two residues off the front to make PYY3-36, which prefers the Y2 receptor, a presynaptic inhibitory receptor on the appetite-driving NPY neurons of the hypothalamus.

Mechanism: Established in humans by infusion: PYY3-36 at postprandial concentrations reduces appetite ratings and ad libitum energy intake for hours, lowers plasma ghrelin, and does so equally in lean and obese people. Established in rodents but contested (see the dispute): peripheral PYY3-36 reduces food intake through the Y2 receptor, an effect absent in Y2 receptor knockout mice, with increased c-Fos in the arcuate nucleus, reduced hypothalamic NPY mRNA and inhibition of NPY neuron firing that disinhibits adjacent POMC neurons.

Regulatory history: Not FDA-approved. No PYY or PYY3-36 product is approved anywhere; native PYY3-36 has been studied in people only by intravenous or subcutaneous infusion.

Approves prescription drugs by indication and polices unapproved products, including peptides sold online. Compounding pharmacies may prepare some compounds under a prescription when the FDA places them on a permitted bulk-substances category.

The classification above is the The Longevity Archive reading of U.S. Food and Drug Administration listings for Peptide YY at the reviewed date, not a legal opinion. Rules change, and importing, prescribing and possessing a compound can each be treated differently. Check the regulator directly before acting on anything here.