What a peptide actually is
A peptide is a short chain of amino acids — generally between two and fifty — joined by peptide bonds. Longer than that and biochemists call it a protein. Your body makes thousands of them: insulin, oxytocin, glucagon and growth hormone are all peptides.
Therapeutic peptides are either exact copies of these natural signals, fragments of them, or modified analogues built to survive longer in the bloodstream. That last point matters: unmodified peptides are usually degraded within minutes.
Signals, not building blocks
The most common misconception is that peptides work like protein powder. They don't. A peptide is a signalling molecule: it binds a receptor and tells a cell to do something it already knows how to do — release growth hormone, migrate into a wound, suppress appetite.
That is also why peptides are usually injected. Digestive enzymes break most of them into inert amino acids, so an oral peptide either needs a special absorption enhancer (like oral semaglutide) or it simply won't reach circulation intact.
How peptides differ from steroids
Anabolic steroids are lipid-based hormones that enter cells directly and alter gene transcription, producing large and often lasting effects on tissue and endocrine function. Peptides act on cell-surface receptors and generally work within the body's existing feedback loops.
That makes most peptides gentler, but 'gentler' is not the same as 'safe'. Growth-hormone secretagogues still raise IGF-1, GLP-1 agonists still change how you eat, and unapproved compounds still carry unknown long-term risk.
The main categories
Almost everything in the consumer space falls into one of a handful of buckets:
- Growth hormone secretagogues — CJC-1295, Ipamorelin, Tesamorelin
- Metabolic and incretin peptides — semaglutide, tirzepatide, AOD-9604
- Repair and recovery — BPC-157, TB-500
- Longevity and mitochondrial — epitalon, SS-31, NAD+
- Neuropeptides — Semax, Selank
- Cosmetic and sexual health — GHK-Cu, PT-141