Evidence Standards

This page explains how we approach the science behind hormone optimization and peptide therapy, and how to read the research summaries throughout this section.

Our Outlook on This Field

We're genuinely optimistic about where hormone optimization and peptide medicine are headed. Many of the compounds covered in this section show real, physiologically plausible promise, and a growing body of patients and providers report meaningful benefit from them in practice. Where the controlled-trial evidence is still thin, we read that as a sign this field deserves more research investment, not as a reason for pessimism; a lot of genuinely useful medicine started exactly where these compounds are now. Our goal on every page is to show you clearly what's been demonstrated, what's still anecdotal or early-stage, and where the open questions are, so you come away encouraged about the real potential here and confident that what you're reading reflects the actual state of the evidence, not marketing.

How GH-Axis and Peptide Therapies Generally Work

Growth hormone is released from the pituitary in pulses, not as a steady stream. The hypothalamus governs this pulsatility through two opposing signals: growth-hormone-releasing hormone (GHRH), which stimulates pituitary somatotrophs to secrete GH, and somatostatin, which suppresses it. Ghrelin and its synthetic mimetics (the growth hormone secretagogue, or GHS, class) act through a separate receptor, GHS-R1a, to amplify the size of each GH pulse and to blunt somatostatin's braking effect.

Much of what patients experience from GH-axis therapy is mediated downstream, through insulin-like growth factor 1 (IGF-1), which the liver produces in response to circulating GH. IGF-1 levels rise and fall more slowly than GH itself, which is why lab monitoring typically tracks IGF-1 rather than GH directly. But GH also has effects of its own, independent of IGF-1: it acts directly on adipocytes to stimulate lipolysis and shift the body toward burning fat, and it has a direct, IGF-1-independent effect on peripheral tissues that reduces insulin sensitivity. Some of the effects patients notice, and some of the effects we monitor for, come from GH acting on its own rather than through IGF-1, so the two should not be treated as a single pathway with one output.

Different compounds in this class act at different points in that pathway. GHRH analogs (sermorelin, tesamorelin, CJC-1295) work through the GHRH receptor. Ghrelin mimetics (ipamorelin, GHRP-2, GHRP-6, hexarelin, MK-677) work through GHS-R1a. Some of these compounds are more selective than others for GH release alone, versus also triggering cortisol, prolactin, or appetite effects, and that selectivity is one of the main things that differentiates compounds within the class.

Peptides outside the GH axis (BPC-157, thymosin beta-4, GHK-Cu, and others) work through unrelated mechanisms, generally involving local tissue repair signaling, angiogenesis, or immune modulation, and each has its own page explaining the relevant pathway.

Reported Benefits Alongside Graded Evidence

Patients and providers using these compounds in practice often report benefits beyond what controlled trials have yet measured; better sleep, faster recovery, improved sense of wellbeing, and similar subjective effects come up often and are worth taking seriously as signals of where future research should look. Each compound page includes what's commonly reported in clinical use, clearly separated from the graded evidence below it, so you can see both what people are experiencing and what's actually been demonstrated in a trial, without the two getting blended into one claim.

How We Grade Evidence

Not all evidence carries the same weight, and we do not present it as though it does. Every claim on a compound page is labeled with one of the following tiers, so you can see at a glance what actually supports it.

Large randomized controlled trial. A blinded, placebo-controlled or active-comparator trial with a meaningful sample size, published in a peer-reviewed journal. This is the strongest tier of human evidence and the standard most FDA-approved drugs were built on.
Small human study. A human trial or cohort that is real and peer-reviewed, but limited by sample size, duration, blinding, or a surrogate rather than clinical endpoint. This evidence is genuine and worth knowing, but it does not carry the same weight as a large controlled trial, and we say so explicitly rather than letting the citation format imply otherwise.
Preclinical or animal-only. Evidence from cell culture or animal models. This is often where a compound's story starts, and it can be genuinely informative about mechanism, but it does not establish that an effect will occur, or occur safely, in humans.
Single-source or unreplicated. Findings that originate from one research group or lab lineage and have not been independently replicated elsewhere. We still cite these when they are the only evidence available, but we flag them as such rather than presenting them with the same confidence as replicated, independent findings.

When a claim would require flattening two different tiers together to sound more impressive, we don't make that claim. When the honest answer is "the evidence for this specific use is thin," we say that instead of filling the gap with a stronger-sounding but less relevant citation.

Mechanism versus Outcome

The tiers above describe how a study was designed. A separate question is what it actually measured, and the two are not the same thing.

A mechanism study shows that a compound does something at the level of a receptor, an enzyme, a cell, or a biomarker: it binds this receptor, it raises this growth factor, it increases collagen synthesis in a dish. An outcome study shows that a compound produces a result a patient actually cares about: less pain, faster healing, more muscle, better function. A mechanism finding does not automatically predict an outcome, because biological systems have other pathways, often not identified or measured in the mechanism study, that can offset, dominate, or redirect what the isolated mechanism would otherwise predict. This gap exists even when the mechanism study itself is well designed and even when it happens to be a large, rigorous trial; a rigorous trial that only measures a surrogate marker still has not shown that the marker translates into the outcome patients want.

Because of this, every evidence entry on a compound page notes not just its design tier but what kind of endpoint it measured; mechanism or surrogate, versus clinical outcome. A compound can look strong on one axis and weak on the other, and both are worth knowing before drawing a conclusion.

Compounded versus FDA-Approved

Some products discussed in this section are FDA-approved medications used on-label or off-label (testosterone, tesamorelin as Egrifta, and others). Many are compounded preparations, prepared by a licensed pharmacy from an active pharmaceutical ingredient, for an individual patient under a provider's prescription.

Compounded medications are not FDA-approved finished products. The FDA has not reviewed a given compounded preparation for safety, efficacy, or manufacturing quality in the way it reviews an approved drug application. This does not mean a compounded preparation is unsafe or inappropriate; it means the manufacturing and efficacy assurances that come with FDA approval do not automatically apply, and that a licensed provider's judgment, plus the pharmacy's own quality standards, are doing the work that FDA review would otherwise do. Every compound page states this plainly rather than leaving it implied.

What Counts as Evidence-Based on This Site

Every source cited in this section is checked against the original publication, not against a summary or a search result, before it is published. If we get something wrong, we correct it and note the correction. We update pages as new evidence is published rather than treating them as fixed once written.

Open Questions as Opportunity

Peptide and hormone-optimization research has real gaps that apply across most of this class of compounds, and we see those gaps as the field's growing edge rather than a strike against it. Long-term safety data beyond the duration of the original trials is often limited or absent, simply because the larger, longer trials haven't been funded yet. Optimal cycling, dosing duration, and discontinuation strategy are rarely defined by controlled research and are frequently extrapolated from short trials or clinical experience, which is exactly the kind of question a well-designed outcomes trial could answer given the right investment. Individual variability in response is significant and not well captured by population-level data. Each compound page names the specific version of these gaps that applies to it, alongside what's already known, so the picture is honest and complete rather than either overstated or discouraging.

Why We Don't Publish Dosing Protocols Here

The pages in this section explain mechanism and evidence because that is public education anyone can use to understand a therapy before deciding whether to pursue it. Dosing, cycling, and administration are individualized clinical decisions that depend on your history, labs, and goals, and they are made in consultation with a provider, not read off a public page. That is the reason every page in this section ends with an invitation to discuss your care with your provider, rather than a protocol table.