[2026 update] Evidence quality in the secretagogue literature: an honest assessment

Posting this under the heading it deserves: Evidence quality in the secretagogue literature: an honest assessment Everything below is what sits behind that.

Comparing STEP 8 (JAMA, 2022) with STEP 1 (N Engl J Med, 2021) and finding the comparison harder than it looks.

Different populations, different durations, different endpoints defined slightly differently, and in one case a different estimand. People compare the headline percentages anyway, including me until recently.

Is there a defensible way to put these side by side, or is the honest answer that there is not and we should stop?

On the opening post — agreed on the reasoning, with one qualification.

IGF-1 as a surrogate: it is a better integrated measure than a spot growth hormone level and it is still a surrogate, with all the caveats that come with surrogates. Stable or rising IGF-1 is not the same as "this is working" in any health-related sense.

Picking up post #2: that is the part I would want checked first.

I disagree with the reply above, and I think the disagreement is substantive rather than terminological.

The distinction being drawn does not survive when you look at the published data for this specific question. I would be glad to be shown wrong on this, because the version I am arguing against is more convenient.

Tesamorelin has an approved indication in HIV-associated lipodystrophy. That is the only compound in this class with a registration-quality evidence base from a proper trial programme. Generalising from that narrow population to healthy adults is a substantial extrapolation.

Development history is more informative than speculation: ipamorelin was investigated clinically for post-operative ileus and was not taken forward to registration. That it was not brought to market tells you something about the cost-benefit calculation that any amount of forum enthusiasm does not.

Two things before anyone answers the substance.

First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound.

This follows post #4 rather than contradicting it.

Secretagogues and glucose tolerance: there is a mechanistic concern that sustained growth hormone elevation might impair glucose tolerance. The clinical relevance of this concern in practice is not well established.

I read post #6 twice before replying, because I had assumed the opposite.

Why this subcategory is stricter about sourcing than most: the evidence base is weaker and that is precisely why documentation quality matters more. A supplier page that clearly identifies the compound and the purity is more valuable for secretagogues than for incretin agonists where the evidence base is stronger.

post #8 answers the question as asked. The question underneath it is different.

Reading a rodent study on a secretagogue without over-extrapolating: rodent studies can show a mechanism is plausible. They cannot show magnitude of effect in humans or safety profile in humans. That gap is larger for secretagogues than for incretin agonists because the human evidence is thinner.

What a well-designed human trial of a secretagogue would look like: randomised, placebo-controlled, adequate sample size, IGF-1 as primary outcome, muscle and strength as secondary outcomes, adequate follow-up duration. Very few secretagogue trials meet that description.

Evidence quality in the secretagogue literature is honestly weaker than in the incretin literature. Large randomised controlled trials are rare. Most evidence is mechanistic or from small studies. This is why this subcategory has higher sourcing standards than most.

Picking up post #9: that is the part I would want checked first.

GHRH analogues versus ghrelin mimetics are often conflated but they are different mechanisms. GHRH analogues (like CJC-1295) cause the pituitary to release growth hormone. Ghrelin mimetics (like GHRPs) act on the ghrelin receptor directly. The effect on growth hormone secretion is similar but the mechanisms are distinct.

CJC-1295 with and without DAC: the version with a drug affinity complex binds albumin covalently and persists for days. The version without it does not persist. Supplier labelling frequently does not distinguish them clearly, so confirming which you have is important.