RESEARCH PEPTIDE FUNDAMENTALS
Research Peptide Fundamentals: What Actually Crossed Into Prescription Medicine
Semaglutide, tirzepatide, and tesamorelin are the peptides most people ask about first — because all three cleared the bar from lab compound to prescribed drug. This desk reads what that bar required, compound by compound, without smoothing over how differently each one cleared it.
Semaglutide
The broadest-approved compound here — five FDA indications and a trial record deep enough to include a head-to-head loss against its successor.
Read the research ›
Tirzepatide
A dual GIP/GLP-1 agonist that beat semaglutide head-to-head, with a confirmed gallbladder-risk signal its own meta-analysis doesn't hide.
Read the research ›
Tesamorelin
The lead compound on this desk — a real FDA approval, but for one condition only. Everything else is off-label.
Read the research ›The short version
mypeptidesrx is a plain-English guide to three peptides that started as laboratory research tools and ended up as prescribed medicines. Semaglutide and tirzepatide are GLP-1-family drugs used for diabetes and weight loss; tesamorelin is a growth-hormone-releasing hormone (GHRH) analogue approved for a narrower use. A peptide is a short chain of amino acids — smaller than a full protein — engineered here to bind a specific hormone receptor and trigger a specific downstream effect.
The word 'prescription' does a lot of hiding here. It can mean 'approved for one specific condition in a defined population, with everything else off-label' (tesamorelin) or 'approved across five separate indications with tens of thousands of trial participants behind it' (semaglutide). This guide keeps that distinction visible instead of collapsing it, because collapsing it is where most peptide marketing goes wrong. Nothing on this site is sold, dosed, or recommended for a person — it summarizes what the published trials and reviews actually found, cited by number, so you can weigh the evidence yourself.
Why these three, together
The organizing idea on this desk is peptides that crossed into prescription medicine — and the research behind them. All three compounds here began as investigational molecules studied in small trials, and all three now carry an FDA approval. That is a real and meaningful bar: it means a sponsor ran controlled trials, a regulator reviewed the safety and efficacy data, and a specific indication was defined narrowly enough to approve.
What differs sharply is how much territory that approval covers. Semaglutide and tirzepatide each carry broad, well-replicated indications — type 2 diabetes, chronic weight management, and (for semaglutide) cardiovascular and kidney outcomes, backed by trials ranging from the thousands to the tens of thousands of participants [1][2][3][4][8][9]. Tesamorelin's approval is narrow by comparison: it is approved for one condition, HIV-associated lipodystrophy, in the population it was actually studied in [11][15]. Nearly everything else said about tesamorelin — general visceral-fat reduction outside HIV, cognitive effects, anti-aging claims — is off-label extrapolation, not label-supported use. Leading with tesamorelin on this desk is a deliberate choice: it is the clearest example of how far 'FDA-approved' can sit from 'broadly studied.'
What a research peptide even is
Peptides are short chains of amino acids, the same molecular building blocks that make up larger proteins. What makes the three compounds here interesting is not that they are peptides — thousands of peptides already exist in the body — but that each one was engineered to survive in circulation long enough to be dosed on a practical schedule, and to bind a receptor with enough selectivity to be useful as a drug.
Semaglutide and tirzepatide are both incretin-receptor agonists: they mimic gut hormones released after eating, engaging the GLP-1 receptor (semaglutide) or both the GLP-1 and GIP receptors (tirzepatide) to affect insulin secretion, appetite, and gastric emptying. Tesamorelin works upstream of that system entirely — it is a modified analogue of growth hormone-releasing hormone (GHRH) that binds pituitary receptors and stimulates the body's own pulsatile release of growth hormone, rather than supplying a hormone directly. Different receptor, different axis, different clinical story — which is exactly why comparing them side by side is useful rather than redundant.
Reading this desk skeptically
This site is written to a specific standard: state plainly what a finding actually shows, in what population, at what dose, and flag it clearly when a claim rests on one trial, an off-label extrapolation, or data that hasn't been replicated. Some findings here are well replicated across large randomized trials — semaglutide's cardiovascular benefit, for instance, comes from a single but very large (17,604-person) outcomes trial [3]. Others rest on much thinner ground — tesamorelin's most recent body-composition meta-analysis pools only five trials [10], and its approved use covers one population only. Where the evidence is thin, this desk says so instead of writing around it. Read each compound page for the specific trial populations, and the comparison page for how the evidence bases actually stack up against each other.