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Biomarker Changes vs Meaningful Health Outcomes: Higher Is Not Better

Why a higher or lower lab number is not the same as feeling or living better, using IGF-1, surrogate endpoints and GH research as plain examples.

Content last updated . This page has not been medically reviewed.

Quick answer
A biomarker is something measured, such as a blood level. A clinical outcome is how a person feels, functions or survives. A change in a biomarker is not automatically a benefit, and "higher" is not automatically "better". This matters for peptide marketing, which often points to a rise in GH or IGF-1 as proof of effect. See also biomarkers and biological age tests.

Evidence labels: established, mixed, preclinical (cells/animals only), marketing claim.

Definitions

TermMeaning
BiomarkerA measured characteristic, such as a hormone level
Clinical outcomeHow a patient feels, functions or survives
Surrogate endpointA trial endpoint used as a substitute for a direct measure of how a patient feels, functions or survives. It does not measure the clinical benefit itself but is expected to predict it. [1]

FDA describes three levels of validation: candidate (still being evaluated), reasonably likely (supported by strong rationale but limited clinical data) and validated (strong evidence that an effect on the surrogate predicts a specific clinical benefit). [1]

So a biomarker can only stand in for benefit if there is evidence that it does. For many peptide claims that evidence has not been shown.

Example 1: IGF-1

A meta-analysis of 19 prospective cohorts (30,876 adults) found a U-shaped link between IGF-1 and death from any cause. Low IGF-1 versus middle was linked with higher mortality (hazard ratio 1.33), and so was high versus middle (hazard ratio 1.23). [2] So "raise IGF-1" has no simple direction. This is observational data and does not prove that changing IGF-1 changes survival.

Fasting and low-calorie research even proposes that lower GH-IGF-1 activity may be tied to cancer protection in rodents, while noting that alternating low and normal levels may be ideal. [3] Label: preclinical (cells/animals only).

Example 2: GH in healthy older adults

In a systematic review of trials, GH therapy changed body composition (fat mass down about 2.1 kg, lean mass up about 2.1 kg) while weight did not change, bone density did not change, and edema, joint pain, carpal tunnel syndrome and breast enlargement were more common. [4] Body composition on a scan is not equal to better function or longer life. See growth hormone and IGF-1 signaling.

Example 3: weight and heart events

Weight loss and blood sugar measures are important, but the SELECT trial counted actual heart attacks, strokes and cardiovascular death to show benefit in its population. [5] See incretin-based medicines: clinical outcomes.

Questions to ask of any claim

  • What exactly was measured: a lab value or an outcome people notice?
  • In whom: cells, animals, or people like me?
  • Compared with what: placebo, no treatment, or nothing?
  • Did the study also report harms and negative results?
  • Who funded it?

These are general reading skills, not a safety test for any product. More in reading early-stage research.

Frequently asked questions

What is a surrogate endpoint?

A trial endpoint used as a substitute for a direct measure of how a patient feels, functions or survives. [1]

Is a higher IGF-1 level better?

Not according to the cohort data summarized: both low and high levels were linked to higher mortality than the middle range. [2]

If a peptide raises GH, is that a benefit?

Not on its own. A higher GH level is a biomarker change. In GH therapy trials in healthy older adults, benefits were limited to body composition and side effects occurred. [4]

Does a clinic's lab report prove a product works?

No. A lab number is not an outcome, and claims should be matched to trial evidence in people.

Where do I check the strength of a claim?

Use how to evaluate peptide claims.

More details: evidence, limits and cautions

The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.

Safety note
Do not change any medicine or start a hormone-related product because of a lab number. Interpretation belongs with a clinician who knows your history.
References
  1. FDA, Surrogate Endpoint Resources for Drug and Biologic Development. U.S. Food and Drug Administration. Read 2026-10-22.
  2. Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis. Aging Cell 2022. Read 2026-10-22.
  3. Nutrition, GH/IGF-1 signaling, and cancer. Endocrine-Related Cancer 2024. Read 2026-10-22.
  4. Systematic review: the safety and efficacy of growth hormone in the healthy elderly. Annals of Internal Medicine 2007. Read 2026-10-22.
  5. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. New England Journal of Medicine 2023 (SELECT). Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.