Sermorelin vs Tesamorelin: How They Differ

Structure and mechanism side by side

Sermorelin and tesamorelin are both analogs of growth hormone-releasing hormone, the hypothalamic peptide that tells the pituitary gland to release growth hormone. Neither supplies growth hormone. Each stimulates the gland to release its own, so the body's feedback control stays in place.

The structures differ. Sermorelin is the first 29 amino acids of the hormone, the fragment the Geref trials called GHRH(1–29) ^{[1, 2]}. Tesamorelin keeps all 44 amino acids of human GHRH and adds a hexenoyl group, a six-carbon chain with a double bond at position 3, to the tyrosine at its amino end ^[10]. Its label states that it binds the human GHRH receptor with a potency similar to the natural hormone, and that it raises growth hormone, IGF-1 and IGFBP-3 ^[10].

The length difference also has a legal consequence. FDA treats an amino acid chain of more than 40 amino acids as a protein, and therefore as a biological product ^[15]. At 44 amino acids tesamorelin crosses that line; at 29 sermorelin does not. The table sets out the rest.

Approval history

Sermorelin reached the market first. Drugs@FDA records two Geref applications: NDA 019863, approved December 28, 1990 as a new molecular entity, and NDA 020443, approved September 26, 1997 as a new dosage form with orphan status ^{[5, 6]}. The sponsor told the FDA on December 2, 2008 that the product was being discontinued; the agency published the withdrawal of approval on May 19, 2009, and on March 4, 2013 it determined that Geref had not been withdrawn from sale for reasons of safety or effectiveness ^[4].

Tesamorelin was approved as EGRIFTA on November 10, 2010 ^[12]. The EGRIFTA SV formulation followed, and on March 25, 2025 the FDA approved EGRIFTA WR under supplement S-020 to the same application ^[12]. Both the EGRIFTA SV and EGRIFTA WR labels were listed on DailyMed in September 2026, and the EGRIFTA WR label states that the two are not substitutable ^{[10, 11]}. On March 23, 2020, between those approvals, the application was deemed a biologics license, BLA 022505, along with the other products on the FDA's transition list ^{[12, 13]}.

Trial record

Sermorelin's trial record is sizable and old. Across the names it is indexed under, PubMed holds 71 clinical trials: 9 published before 1990, 57 in the 1990s, 5 between 2000 and 2009, and none since, the most recent from 2005 ^[3]. The approval-era evidence is pediatric: a one-year open-label study in 110 children with growth hormone deficiency found that height velocity rose from 4.1 to 7.2 centimeters a year after twelve months ^[1]. The adult trials are small. In one, nightly injections in 11 men aged 64 to 76 raised nocturnal growth hormone without changing IGF-1 or the scan measures of muscle and fat ^[2]. Sermorelin versus growth hormone reads the adult trials in full.

Tesamorelin's record is modern and concentrated in one population. In a phase 3 trial of 404 adults with HIV and excess abdominal fat, visceral fat fell 10.9 percent with tesamorelin against 0.6 percent with placebo over six months ^[7]. Of 26 papers carrying the randomized-trial publication type, 20 name HIV or lipodystrophy ^[9]. Outside HIV, a twelve-month trial in 60 abdominally obese adults with reduced growth hormone secretion found visceral fat fell 35 square centimeters against placebo, with no significant change in fat under the skin ^[8].

Neither record supports general fat loss. The tesamorelin label states that it is not indicated for weight loss management because its effect on weight is neutral ^[10], and tesamorelin off-label covers the trials outside HIV. Sermorelin has no modern trial of body composition at all ^[3].

Labeled safety then and now

Sermorelin has no current label to consult. Drugs@FDA marks both Geref applications as discontinued and holds no label for either ^{[5, 6]}, so its safety record is the trials. In the pediatric study, treatment was well tolerated, with no adverse changes in blood chemistry or hormone measures, no change in fasting glucose and no excessive rise in IGF-1 ^[1]. The trials were small and none was sized to detect uncommon harms.

Tesamorelin carries a current label, and its warnings follow from raising growth hormone. The most common adverse reactions, each above 5 percent, are arthralgia, injection site erythema and pruritus, pain in an extremity, peripheral edema and myalgia ^[10]. The warnings cover fluid retention, glucose intolerance, with 5 percent of treated patients against 1 percent on placebo reaching an HbA1c of 6.5 percent or higher, raised IGF-1 whose long-term effects are unknown, hypersensitivity reactions in 4 percent, and an increased risk of neoplasms ^[10]. It is contraindicated in pregnancy, active malignancy and disruption of the hypothalamic-pituitary axis ^[10].

Because the two share a mechanism, questions about IGF-1 and glucose apply in principle to both. The difference is that tesamorelin's label measured them in a controlled population, and sermorelin's small, older trials did not measure them at that scale.

Who can lawfully supply each today?

Sermorelin is compoundable. Licensed 503A pharmacies prepare it against a valid prescription, and its history as the active ingredient of an approved drug, withdrawn on a commercial decision the FDA confirmed in writing, underpins that position ^[4]. The sermorelin monograph records the status with its verification date.

Tesamorelin is approved, and only the licensed product is lawful. Its application became a biologics license on March 23, 2020 ^{[12, 13]}, and the FDA's notice to compounders states that biological products that transitioned that day are not eligible for the compounding exemptions in sections 503A and 503B ^[14]. A compounded tesamorelin therefore has no lawful route under either section. The tesamorelin monograph records the approval and the label.

For both molecules, material sold without a prescription as research-use-only product sits outside pharmacy quality standards, whatever the molecule's own status.

Where does ipamorelin fit?

Ipamorelin is often grouped with these two, but it is not a GHRH analog. It is a ghrelin mimetic, an agonist at the ghrelin receptor rather than the GHRH receptor ^[16]. Its one randomized efficacy trial, in postoperative ileus, did not reach statistical significance ^[16].

Its legal position differs from both. Ipamorelin's 503A nominations were withdrawn in 2024, FDA keeps it in Category 2 under the separate 503B policy, and it has no lawful compounding route. The GH secretagogues class page sets the three side by side with the rest of the class.

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