Read a little further.

Different sources answer different questions.

The age-related measurements explain why these four signals draw attention. They do not establish that administering the matching option changes the course of aging. A paper about a precursor is not a trial of NAD+ itself, and a study of free GHK is not automatically a study of GHK-Cu.

The FDA material concerns regulatory status and the limits of available evidence. It cannot supply a missing clinical result.

• NAD+ and aging cells

  2013 · Tissue NAD+ and cellular communication in aging research, including mechanistic work in mice.

  DOI: 10.1016/j.cell.2013.11.037

• An early NAD+ infusion study

  2019 · A small exploratory human infusion study measuring blood and urine metabolites, rather than long-term aging outcomes.

  DOI: 10.3389/fnagi.2019.00257

• A controlled oral precursor study

  2018 · A controlled human study of oral nicotinamide riboside, which is a precursor rather than direct NAD+ treatment.

  DOI: 10.1038/s41467-018-03421-7

• MOTS-c in aging men

  2020 · Observational measurements in healthy men, with different age patterns in blood and muscle.

  DOI: 10.18632/aging.102944

• MOTS-c in exercise and mouse research

  2021 · Research on the natural exercise signal alongside experiments administering MOTS-c to mice of different ages.

  DOI: 10.1038/s41467-020-20790-0

• FDA’s MOTS-c evidence assessment

  2026 · FDA staff’s review of the available MOTS-c evidence, including substantial human and animal safety gaps.

  https://www.fda.gov/media/193347/download

• Growth-hormone signaling in older men

  1999 · Human research investigating GHRH signaling and age-related differences in nighttime growth-hormone output.

  DOI: 10.1210/jcem.84.10.6063

• GHRH in a small older-adult study

  1992 · A small study measuring growth hormone and IGF-1 responses in older men, without establishing longevity benefit.

  DOI: 10.1210/jcem.75.2.1379256

• FDA’s determination on former sermorelin products

  2013 · The FDA determination distinguishes the former products’ withdrawal from a withdrawal for safety or effectiveness reasons.

  https://www.federalregister.gov/d/2013-04827

• FDA guidance on patient-specific compounding

  2025 · FDA guidance relevant to components of previously approved drugs and patient-specific pharmacy preparation.

  https://www.fda.gov/media/174456/download

• GHK, aging and preclinical research

  2020 · A review connecting the plasma GHK age observation with cell and animal research; it is not a human injection trial.

  DOI: 10.31491/apt.2020.03.014

• GHK and gene activity in lung cells

  2012 · Research involving free GHK and human lung cells, distinct from clinical treatment with GHK-Cu.

  DOI: 10.1186/gm367

• FDA’s peptide safety concerns

  2026 · FDA’s safety concerns and withdrawn-nomination entries; the page identifies April 22, 2026 as its current date.

  https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks

• FDA’s cosmetic and drug distinction

  2022 · FDA’s explanation of when intended use places an anti-aging product under drug rules rather than cosmetic rules.

  https://www.fda.gov/cosmetics/cosmetic-products/wrinkle-treatments-and-other-anti-aging-products

• FDA’s explanation of compounding

  2025 · FDA’s account of pharmacy preparation and the absence of approval for compounded medicines.

  https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers

Reading beyond a headline

The four-signal overview connects the measurements without treating them as treatment targets. The comparison keeps each substance and research setting distinct. A reported change in cells, animals or a blood measurement needs to remain attached to that setting when it is discussed elsewhere.

A provider’s assessment through Promise Peptides cannot supply missing research evidence.