What are peptides?

What is a peptide?

A peptide is a short chain of amino acids. Amino acids are the same building blocks that proteins are made of, but proteins are much longer chains. There is no sharp line between the two.

The peptides we write about vary a lot in size. KPV and GHK-Cu are made of only three amino acids. Semax has seven. MOTS-c has 16.^[1]

Which peptides does the body make itself?

The body uses peptides as signals. GLP-1 is one example. It is released from the gut when we eat, and it helps the pancreas make insulin and helps us feel full.^[2] Alpha-MSH is another. Among other things, it affects skin pigment and inflammation.^[3]

Many of the peptides being researched are synthetic versions or fragments of such substances. Researchers test them first in the laboratory and then in humans.

Peptides as medicines

Insulin was first used as a medicine almost a hundred years ago. Since then, more than 80 peptides have been approved as medicines, for conditions such as diabetes, cancer and osteoporosis.^[4]

The best known today are semaglutide and tirzepatide. Both are approved in the EU and available on prescription.^[5][6]

Why do peptides make good medicines?

Peptides often work in a very targeted way, because they resemble the signals the body uses itself. When they have done their job, they are broken down into amino acids, the same building blocks we get from food. This is why approved peptide medicines are generally considered well tolerated, and why more and more new medicines are peptides.^[4]

Four kinds of peptides, four sets of rules

What decides which rules apply is not that something is a peptide. It is what the product is, and how it is used.

1. Approved medicines have been tested in large studies, assessed by the medicines agencies and are prescribed by a doctor.^[5]
2. Medicines in clinical trials, such as retatrutide, have been tested in large studies in humans and are on their way to approval.^[7]
3. Cosmetic ingredients, such as GHK-Cu in skin creams, are applied to the skin and regulated as cosmetics.
4. Research compounds, such as BPC-157 and TB-500, are still being studied.

The rules for each kind are explained in Rules in Norway.

Why are peptides so talked about now?

Peptide medicines such as semaglutide have made peptides known to many people. At the same time, interest in peptides in training and sport is growing. Many of these substances are promising in the laboratory, and research in humans is under way.^[8]

How do I know what the research says?

For each peptide we show how far the research has come, and whether it comes from humans, animals or cells. Read How to read a study to see how you can assess a study yourself.