Sermorelin vs. Tesamorelin: What the Trials Actually Found

Same family, opposite records

Both compounds are growth hormone-releasing hormone rebuilt in a laboratory. Sermorelin is the first 29 amino acids of the hormone, the shortest fragment that still makes the pituitary answer, which is why you see it written GHRH(1-29). Tesamorelin is a synthetic analog of the longer form; the pooled analysis of its two phase 3 trials describes it as GHRH(1-44) ⁴. Neither supplies growth hormone. Both ask the body for its own.

That is where the resemblance stops. One of them has two multicenter phase 3 trials, a pooled analysis, a 52-week extension and a current FDA approval. The other has a randomized record that closed in 2005 and an approval that lapsed. Nothing about the shared mechanism transfers the first record onto the second.

What tesamorelin's trials measured

The pivotal trial randomized 412 adults on antiretroviral therapy with excess abdominal fat to 2 mg of tesamorelin or placebo daily for 26 weeks. Visceral fat fell 15.2% against a 5.0% increase on placebo, and IGF-1 rose 81.0% against a 5.0% fall ³.

Pooling both phase 3 trials gives 806 patients randomized 2:1, and it also gives the finding that matters most for how this drug gets sold. The 26-week treatment effect on visceral fat was −15.4%. The treatment effect on the subcutaneous fat under the skin was −0.6%, and it was not statistically significant ⁴. The drug moved fat out of one compartment. It did not take it off the body.

At week 26 patients were re-randomized, and the 246 who stayed on tesamorelin held a 17.5% visceral fat reduction at week 52 ⁴. The extension answered the question people actually ask, too, and the answer is blunt: on discontinuation, visceral fat reaccumulated, and the authors concluded that the effects do not last beyond the duration of treatment ⁵.

What sermorelin's trials measured

A PubMed search restricted to the randomized-controlled-trial publication type returns 19 records for sermorelin. The earliest was published in 1986 and the most recent in 2005. Most of the set is pituitary physiology — what the growth hormone response looks like after a bolus, what happens when you block a receptor pathway, how the response compares against other releasing peptides — and a smaller part is diagnostic dose-response work.

The two trials in the table are the closest thing in that record to a treatment trial. One randomized 60 children with growth hormone deficiency into three equal groups for six months: two doses of GHRH(1-29)-NH2, or growth hormone itself. Mean height velocities were 9.2 and 9.3 cm per year on the two GHRH doses against 14.6 cm per year on growth hormone, and the authors concluded that the treatment is unlikely to be as effective as growth hormone for promoting growth ¹. The other randomized 43 prepubertal children to a low dose, a high dose, or growth hormone, also for six months; height velocity was lowest in the low-dose group and comparable in the high-dose and growth hormone groups, while an increase in height standard deviation score for bone age occurred only in the children given growth hormone ².

Read the population again, because it is the whole point. Those are children who were not growing. Nobody in either trial was a healthy adult taking an injection for energy, recovery or body composition.

A note on the phase column. Neither 1993 trial was registered or phase-labeled — the convention did not exist yet. They are recorded above at the phase their design corresponds to: randomized comparative dosing in the patient population the drug was developed for. PubMed's own indexing attaches a phase to exactly one of sermorelin's 19 randomized trials, a 2005 phase 1 study of a long-acting conjugated version in healthy volunteers.

Two approvals, only one of them current

This is the cleanest contrast on the page, and it comes from the FDA's own database rather than from anybody's marketing.

Tesamorelin sits under BLA022505, sponsored by Theratechnologies, and every product record under it reads Prescription. It is a marketed drug today. The approval is also narrow: as of August 2026 the label gives one indication, the reduction of excess abdominal fat in HIV-infected adults with lipodystrophy, and its Limitations of Use state that it is not indicated for weight loss management because its effect is weight neutral.

Sermorelin sits under two applications, NDA019863 and NDA020443, sponsored by EMD Serono and marketed as Geref. Every product record under both reads Discontinued. One detail deserves to travel with that word: each strength carries a Federal Register determination that the product was not discontinued or withdrawn for safety or effectiveness reasons. Geref left the market; it was not pulled off it. What follows is still that the approved product no longer exists, so every unit of sermorelin sold today is a compounded preparation rather than the drug those 19 trials studied. Our compounding explainer covers what that distinction does and does not guarantee.

The trial nobody has run

A reader comparing these two is usually asking one question: which one does more for body composition in a healthy adult? Neither record answers it.

Tesamorelin's answer is bounded by its population. Its trials enrolled adults with HIV-associated fat accumulation, and its own label says the effect on total body weight is neutral. Extending a 15% visceral fat reduction in that group into a body recomposition claim for someone without the condition is extending it past what was randomized.

Sermorelin's answer is missing rather than bounded. No trial in its randomized set used fat mass, lean mass, sleep quality or recovery as an endpoint. The closest anyone has come is a 1997 single-blind, randomized, placebo-controlled trial in the Journal of Clinical Endocrinology and Metabolism, which gave 19 adults aged 55 to 71 a norleucine-substituted GHRH(1-29) analog — a modified molecule, not sermorelin — nightly for 16 weeks after four weeks of placebo injections. Lean body mass rose in the men and not the women, skin thickness rose in both, sleep quality was unaffected in either, and there were no other changes in body composition or bone mineral density. That is one small trial, of a related molecule, twenty-nine years ago, and it is the strongest thing in the neighborhood.

The bottom line

These are two different kinds of claim wearing the same mechanism. Tesamorelin has modern phase 3 evidence for a specific effect in a specific population, an approval that is live today, and a published account of what happens when treatment stops. Sermorelin has a real randomized record, and it is an old one about how the pituitary works and how children grow, attached to an approval that expired. If you are choosing between them for a use neither was tested for, the honest answer is that the trial has not been run — and the compound with more trials behind it is the one whose label states plainly that it is not for weight loss.