Comparison
Tesamorelin vs Ipamorelin
Both peptides raise growth hormone, but through different receptors. Tesamorelin mimics GHRH; ipamorelin mimics ghrelin.
Tesamorelin vs Ipamorelin at a glance
| Tesamorelin | Ipamorelin | |
|---|---|---|
| Receptor | GHRH receptor | Ghrelin receptor (GHS-R1a) |
| Size | 44 amino acids | 5 amino acids |
| Approval | FDA-approved (Egrifta) 2010 | Not approved |
| Best evidence | Phase 3: −15–18% visceral fat | Animal GH-release data; failed ileus trials |
| Cortisol/prolactin effect | Minimal | Minimal (its main selling point) |
How they work
Tesamorelin
Tesamorelin is the full 44-amino-acid GHRH sequence with a trans-3-hexenoyl group attached to the first amino acid, which protects it from rapid breakdown by DPP-4. It binds GHRH receptors in the pituitary, increasing growth hormone and downstream IGF-1. Growth hormone preferentially mobilises visceral fat, which is why VAT fell in trials while subcutaneous fat changed less.
Ipamorelin
Ghrelin, the “hunger hormone”, also stimulates growth hormone through GHS-R1a receptors in the pituitary and hypothalamus. Ipamorelin mimics this specific action. Each dose produces a distinct GH pulse, peaking within about 30–60 minutes. Pairing it with a GHRH analogue (like CJC-1295) amplifies the pulse because the two pathways are synergistic.
Side effects compared
Tesamorelin
- Injection-site redness, itching and pain.
- Joint pain, muscle pain and swelling in the hands/feet (fluid retention typical of raised growth hormone).
- Raised blood glucose — monitoring is advised in diabetes.
- Raised IGF-1; contraindicated in active cancer and pregnancy.
Ipamorelin
In the postoperative ileus trials, adverse events were similar to placebo. Commonly reported effects in non-clinical use include headache, flushing, water retention and injection-site irritation. Raised GH and IGF-1 may reduce insulin sensitivity.
Bottom line
Tesamorelin has far stronger clinical evidence, specifically for visceral fat. Ipamorelin is mostly used in research combinations with CJC-1295.
Frequently asked questions
What is the main difference between Tesamorelin and Ipamorelin?
Receptor: Tesamorelin — GHRH receptor; Ipamorelin — Ghrelin receptor (GHS-R1a).
Is Tesamorelin or Ipamorelin licensed in the UK?
Tesamorelin is not licensed in the UK or EU — the European marketing application was withdrawn in 2013. Ipamorelin is not licensed in the UK or elsewhere.