Sermorelin vs. Tesamorelin (Egrifta): When to Pick One, When to Stack, and How to Do It Safely

What is the difference between sermorelin and tesamorelin?

Sermorelin is a 29-amino-acid analogue of human growth hormone-releasing hormone, the shortest synthetic peptide that carries GHRH's full biological activity [3]. Tesamorelin is the 44-amino-acid human growth hormone-releasing factor sequence with a hexenoyl group on the N-terminal tyrosine, molecular weight about 5,135.9 Da [2].

Neither is growth hormone. Both act on the pituitary to stimulate release of the body's own GH [3][2]. For tesamorelin, the label says GH then raises IGF-1 and IGFBP-3, and the trials showed no clinically significant changes in TSH, LH, ACTH or prolactin [2]. In older men, sermorelin twice daily also raised IGF-1 [19].

The practical difference is regulatory and clinical, not mechanistic: one is an approved prescription drug with a specific indication and phase 3 trials behind it, and the other is a peptide with no approved product on the US market.

Is sermorelin FDA-approved today?

No. Sermorelin acetate was once approved as Geref under two applications: NDA 019863, the 0.05 mg/ampule product approved December 28, 1990 for evaluating the pituitary's ability to secrete growth hormone, and NDA 020443, the 0.5 mg and 1 mg vials approved September 26, 1997 for treating idiopathic growth hormone deficiency in children with growth failure [1]. Geref was never approved for adults, anti-aging, weight loss or athletic performance [1].

The manufacturer discontinued both products in 2008 and asked FDA to withdraw the applications, which FDA did effective June 18, 2009 [1]. In March 2013 FDA determined that Geref had not been withdrawn for reasons of safety or effectiveness [1][8]. That determination does not restore approval.

Sermorelin products available in the US today are compounded, not FDA-approved; FDA does not review compounded drugs for safety, effectiveness or quality before marketing [5]. FDA has not placed sermorelin on its list of bulk substances that may present significant safety risks [9]; it sits in category 1 (under evaluation) on the list for outsourcing facilities [10] and appears in no category on the list for state-licensed pharmacies and physicians [11].

What exactly is tesamorelin approved for?

Egrifta was first approved November 10, 2010 as BLA 022505 [12]. Its only approved use is reduction of excess abdominal fat in HIV-infected adults with lipodystrophy [2][4]. The label adds three limitations: long-term cardiovascular safety has not been established, treatment should be reconsidered in people who have not lost visceral fat, and it is not indicated for weight loss because its effect on weight is neutral [2].

The current products are Egrifta SV (2 mg vial; the label dose is 1.4 mg or 0.35 mL injected subcutaneously into the abdomen once daily) and Egrifta WR (11.6 mg vial; 1.28 mg or 0.16 mL once daily) [2][4]. The labels differ in dose, reconstitution and storage, and state that the two are not substitutable [4]. The phase 3 trials used 2 mg daily of the original 1 mg/vial product; FDA accepted the SV dose because its exposure was similar to that of the 2 mg dose [2].

What do the tesamorelin trials show?

In the first phase 3 trial (Falutz et al., NEJM, 2007), 412 HIV-infected adults with excess abdominal fat received tesamorelin 2 mg or placebo daily for 26 weeks. Visceral adipose tissue measured by CT fell 15.2% on tesamorelin and rose 5.0% on placebo; triglycerides fell 50 mg/dL versus a 9 mg/dL rise; IGF-1 rose 81.0% versus a 5.0% fall (P<0.001 for all) [13].

In the second trial (Falutz et al., JAIDS, 2010), 404 patients were randomized 2:1. At 6 months, visceral fat fell 10.9% (-21 cm2) with tesamorelin and fell 0.6% (-1 cm2) with placebo (P<0.0001), and glucose parameters did not change [14].

A pooled analysis of both trials, 806 patients, found visceral fat changed by -24 versus +2 cm2, a 15.4% treatment effect, with triglycerides -37 versus +6 mg/dL and IGF-1 +108 versus -7 ng/mL [15].

Smaller studies extend the picture. In 50 patients, tesamorelin reduced visceral fat by 34 cm2 while placebo rose 8 cm2, and median liver fat fell 2.0% versus a 0.9% rise [16]. In 61 people with HIV and fatty liver, tesamorelin lowered liver fat by an absolute 4.1 percentage points more than placebo over 12 months; fatty liver is not an approved use [17].

Visceral fat loss is not permanent. In the extension phases, people who continued tesamorelin held visceral fat at roughly 0 to -5% from week 26 to week 52, while those switched to placebo regained 16% to 22% [2].

What do the sermorelin studies show?

The largest sermorelin trial was in children. One hundred ten previously untreated prepubertal children with growth hormone deficiency received 30 micrograms/kg subcutaneously at bedtime for up to a year in an open-label, multicenter study; 86 were evaluable. Height velocity rose from 4.1 cm/yr at baseline to 8.0 cm/yr at 6 months and 7.2 cm/yr at 12 months, 74% were good responders at 6 months, fasting glucose did not change, IGF-1 was not excessively raised, and the drug was well tolerated [18].

In adults, the main study is small and physiological. Ten healthy older men (mean age 68) took 0.5 mg and 1 mg of GHRH(1-29) subcutaneously twice daily for 14 days each, alongside nine young men. At the higher dose, 24-hour growth hormone and IGF-1 rose to levels not significantly different from the young men [19]. That study measured hormone levels and was not designed to show a clinical benefit.

Can you stack sermorelin with tesamorelin?

There is no labeled combination regimen and no studied dose for the pair; the Egrifta labels cover tesamorelin used alone [2][4].

Both peptides raise growth hormone and IGF-1 [3][2][19]. The Egrifta labels ask prescribers to monitor IGF-1 and to consider stopping when IGF-1 stays elevated, for example above 3 SDS, especially if fat loss is not robust; among people treated for 26 weeks, 47% had IGF-1 above 2 SDS and 36% above 3 SDS, and at 52 weeks the figures were 34% and 23% [2]. The labels also warn about glucose intolerance, fluid retention and new or recurrent malignancy [2]. In sermorelin's one-year pediatric study, no adverse changes in general biochemistry or hormone tests appeared and fasting glucose was unchanged [18].

Which one fits which situation?

Tesamorelin is the choice with an approved, on-label use: an HIV-infected adult with lipodystrophy and excess abdominal fat, for which the labels give 1.4 mg daily (SV) or 1.28 mg daily (WR) [2][4]. Used for anything else, such as general fat loss, anti-aging, or body composition in people without HIV, it is outside the label, and the label itself says the drug is not indicated for weight loss management [2].

Sermorelin has no approved use in any population today [1], and the adult human data consist of a short hormone study, not body-composition outcomes [19].

In sport, the question is closed either way: WADA's Prohibited List names sermorelin and tesamorelin in S2.2.4 as growth hormone releasing factors, prohibited at all times, in and out of competition, on both the 2026 and 2027 Lists [6][7].

What the Egrifta labels say to watch

The labels contraindicate tesamorelin in pregnancy, active malignancy, known hypersensitivity to tesamorelin or its excipients, and disruption of the hypothalamic-pituitary axis such as hypophysectomy, hypopituitarism, pituitary tumor or surgery, head irradiation or head trauma [2][4]. In rats, exposure at roughly two to four times the clinical dose produced hydrocephalus in offspring [2].

Glucose intolerance or diabetes can occur during treatment. HbA1c of 6.5% or higher developed in 5% of tesamorelin-treated patients versus 1% on placebo by week 26, a hazard ratio of about 3.3 (95% CI 1.4 to 9.6), and the label asks for glucose evaluation before and during treatment plus regular eye monitoring in people with diabetes [2].

Other labeled effects: fluid retention with edema, joint pain and carpal tunnel syndrome; hypersensitivity reactions in 4% (itching, redness, flushing, hives, rash), for which the label says to seek immediate medical attention and stop; and injection-site reactions in 25% versus 14% on placebo [2]. Most common reactions above 5% were joint pain, injection-site redness and itching, extremity pain, peripheral edema and muscle pain; in the combined table, joint pain was 13% versus 11%, peripheral edema 6% versus 2% and muscle pain 6% versus 2% [2].

Two interactions are spelled out. Growth hormone inhibits an enzyme that helps convert cortisone to cortisol and prednisone to prednisolone. The label says people taking glucocorticoid replacement for hypoadrenalism may need higher maintenance or stress doses after starting tesamorelin [2]. GH may also alter clearance of drugs metabolized by CYP450 enzymes such as corticosteroids, sex steroids, anticonvulsants and cyclosporine; in healthy subjects, simvastatin exposure changed by about 8% and ritonavir exposure by about 9% (lower), which the label calls no significant impact [2].

Pediatric safety and effectiveness are not established, and in children with open growth plates the drug may accelerate linear growth; there is no information in people over 65 [2]. The label also says to consider stopping in critically ill patients, because pharmacologic growth hormone has been linked to increased mortality in acute critical illness [2].