Tesamorelin and ipamorelin are often mentioned together in material about growth hormone, but they are not versions of the same drug. Tesamorelin follows the logic of GHRH, the growth hormone releasing hormone. Ipamorelin belongs to a different group: growth hormone secretagogues acting through the ghrelin receptor GHSR.[1]
A short comparison
| Feature | Tesamorelin | Ipamorelin |
|---|---|---|
| Pharmacological class | Synthetic GHRH analogue | Pentapeptide growth hormone secretagogue |
| Primary target | GHRH receptor on pituitary somatotrophs | Growth hormone secretagogue receptor, GHSR |
| Signalling logic | Recreates a GHRH stimulus | Recreates part of ghrelin-system signalling |
| Human evidence | Controlled clinical studies in a specific population | Early pharmacokinetic and clinical studies, with a different evidence base |
Tesamorelin stimulates the GHRH receptor. Clinical studies showed increased endogenous growth hormone secretion and IGF-1 concentrations. One of the largest evidence bases concerns people with HIV-associated excess visceral fat.[3] That does not transfer the findings to other populations or questions.
Ipamorelin acts through GHSR, a receptor system linked to ghrelin. In preclinical work it released growth hormone through a GHRP-like receptor that is distinct from the GHRH receptor.[1] In a small volunteer study, its terminal half-life after intravenous administration was about two hours.[2]
Why they are not interchangeable
Different receptors mean different pharmacological logic. Evidence for one class does not become evidence for another simply because both can affect growth hormone secretion. Results, formulations, routes and numerical regimens from separate studies should not be mixed.
For the underlying sources, start with the individual monographs for tesamorelin and ipamorelin. They describe the source base and its limits for each substance in more detail.
A broader overview of tesamorelin itself, covering the clinical work and the limits of the evidence, is kept separately: tesamorelin and what the research says.
The full list of sources with links, is in the monographs: Tesamorelin, Ipamorelin.
