# Give the body’s peptide and the treatment their own questions

“The body makes something like it” is an interesting fact. We still want to know what happens when a particular substance is used as a treatment.

![An adult sets down a fork beside a partly eaten lunch at a home dining table.](/health-speech-9bfe27512422/wall-side-pause.webp)

A fork set down, with some lunch still on the plate.

## The biology is only part of the answer

Semaglutide is related to GLP-1, a gut hormone, but has been altered. Tirzepatide acts on the receptors where two gut hormones, GIP and GLP-1, have their effects. Their [semaglutide](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ee06186f-2aa3-4990-a760-757579d8f77b) and [tirzepatide](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=487cd7e7-434c-4925-99fa-aa80b1cc776b) labels explain those actions. Neither fact answers whether a medicine suits a particular person.

We keep two questions apart: “What does it do in the body?” and “Has it helped people with this problem?” An interesting answer to the first cannot fill in a missing answer to the second.

NAD+ belongs in a different group altogether. It’s a coenzyme, a helper for chemical reactions in cells, rather than a peptide. Its [role in cell energy](https://pubmed.ncbi.nlm.nih.gov/20007326/) is background biology, not evidence that an infusion improves health.

## Approval belongs to a particular medicine

There are FDA-approved medicines containing semaglutide and tirzepatide. In separate [semaglutide](https://pubmed.ncbi.nlm.nih.gov/33567185/) and [tirzepatide](https://pubmed.ncbi.nlm.nih.gov/35658024/) trials, people receiving the medicines lost more weight than those receiving placebo, a comparison without the active medicine. Participants had obesity, or overweight with a weight-related condition, and no diabetes. Both trials included lifestyle support.

Their safety information matters too. Both medicines commonly cause stomach problems. Their [labels carry boxed warnings, the FDA’s strongest kind](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ee06186f-2aa3-4990-a760-757579d8f77b), about thyroid tumours seen in rodents, with human relevance unknown. The [tirzepatide label](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=487cd7e7-434c-4925-99fa-aa80b1cc776b) and semaglutide label rule out use with a personal or family history of a rare thyroid cancer called medullary thyroid cancer, or MEN 2, an inherited condition.

For women who haven’t reached menopause, there is an [FDA-approved bremelanotide injection](https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=8c9607a2-5b57-4a59-b159-cf196deebdd9) for distressing low sexual desire. Bremelanotide is also called PT-141, but research chemicals sold under that name don’t share the approval. It must have developed after a period without that problem, occur across situations and have other causes excluded. It isn’t approved for sexual performance. It can cause nausea and temporary blood-pressure rises; the label rules it out with uncontrolled high blood pressure or known cardiovascular disease.

## Compounding doesn’t bring FDA approval with it

Compounding means making a medicine to meet a patient’s particular need. [FDA explains that role](https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers). A compounded medicine is [not FDA-approved](https://www.fda.gov/drugs/human-drug-compounding/understanding-risks-compounded-drugs); FDA doesn’t check its safety, effectiveness or quality before it’s sold. An ingredient name shared with an approved medicine doesn’t change that.

Research chemicals are another category. BPC-157 has [no FDA-approved use](https://www.fda.gov/media/193343/download). “Research use only” is no substitute for evidence of benefit in people.

On FDA’s page current as of April 22, 2026, BPC-157 and GHK-Cu for injectable routes appear under [nominations that were withdrawn](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks). This is not clearance, approval for compounding or Category 1 status. FDA gives no individual withdrawal dates and still lists safety concerns. Our [evidence chapter](/evidence-in-everyday-life) explains the human research; [care questions](/care-conversation) help connect it with a personal concern.

Leave some space for whatever you wonder about next.

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