Sermorelin vs Tesamorelin

Origin and structure

Sermorelin corresponds to the active N-terminal 29-residue fragment of native GHRH (GRF 1-29). It was approved by the FDA in 1997 under the brand name Geref for paediatric growth-hormone-deficiency diagnosis and treatment, before the manufacturer voluntarily withdrew it from US commercial distribution in 2008 for commercial rather than safety reasons.

Tesamorelin reproduces the complete 44-amino-acid native GHRH sequence and carries an additional N-terminal trans-3-hexenoic acid modification that confers resistance to dipeptidyl-peptidase IV degradation. Developed by Theratechnologies as TH9507, it remains an actively marketed, FDA-approved medicine (Egrifta, approved 2010) for HIV-associated lipodystrophy — the only GHRH analogue with a current licensed indication in a major regulatory market.

Mechanism

Both peptides bind the same GHRH receptor on anterior pituitary somatotrophs, triggering Gs-coupled adenylate cyclase signalling and pulsatile GH release from pituitary stores. Both preserve normal negative feedback from circulating IGF-1, GH and hypothalamic somatostatin, distinguishing GHRH-receptor agonism from recombinant GH administration, which bypasses this feedback loop entirely.

The pharmacological difference lies in duration and selectivity. Sermorelin's short plasma half-life (10-20 minutes) produces a brief pulsatile GH release approximating a single natural GHRH pulse. Tesamorelin's longer half-life (26-38 minutes) and once-daily dosing produce more consistent receptor engagement, and its full-length structure is associated with a disproportionate effect on visceral rather than subcutaneous adipose tissue — the specific mechanism underlying its licensed lipodystrophy indication.

Evidence base

Sermorelin's evidence base rests on its 1996-97 paediatric licensing trials and smaller subsequent adult pilot studies on IGF-1 restoration and body composition (Walker et al. 2001; Sigalos & Pastuszak 2018). Tesamorelin's evidence base is considerably larger and more rigorous: a pivotal phase III trial of 412 HIV-infected adults (Falutz et al., N Engl J Med 2007) demonstrated 15-18% visceral-fat reduction versus placebo, with a pooled 52-week safety-extension analysis (Falutz et al. 2010) supporting FDA approval.

Tesamorelin has also generated off-label research interest beyond its licensed indication, including an NIH-funded RCT reporting improved executive function in older adults with mild cognitive impairment (Baker et al., Arch Neurol 2012), and hepatic-fat reduction trials in HIV-associated fatty liver disease (Stanley et al., JAMA 2014; Lancet HIV 2019).

Research positioning

Sermorelin is studied in the context of age-related GH decline (the "somatopause"), where the argument is that pituitary capacity is largely preserved even as hypothalamic GHRH output falls — making GHRH-receptor stimulation a physiologically conservative alternative to exogenous GH. Tesamorelin's licensed role is narrow and specific (HIV-lipodystrophy visceral-fat reduction), but its off-label research use has expanded into cognitive-function and hepatic-fat contexts relevant to broader healthy-ageing interest, backed by a substantially deeper clinical trial record than sermorelin can offer.

Summary table

For the full evidence base, see the individual pages: Read the full Sermorelin entry and Read the full Tesamorelin entry.