GH secretagogues: a complete guide to evidence and safety

What growth hormone secretagogues are

A growth hormone secretagogue is any compound that makes the anterior pituitary release more growth hormone (GH). The difference from recombinant GH is fundamental: exogenous GH enters the blood from outside, while a secretagogue lets the gland release its own, so the response stays subject to the axis's feedback and insulin-like growth factor 1 (IGF-1) rises with it¹⁴¹².

In practice there are two families. The first is the growth hormone-releasing hormone (GHRH) analogs: sermorelin, which is the first 29 amino acids of natural GHRH¹; tesamorelin, which keeps the 44 amino acids of human growth hormone-releasing factor with a hexenoyl group at the N-terminus¹²; and CJC-1295, a GHRH(1-29) modified to bind albumin¹⁵. The second is the ghrelin receptor agonists: the growth hormone-releasing peptides (GHRPs), such as GHRP-6²⁰, and ipamorelin, described in 1998 as the first selective secretagogue²². Ibutamoren (MK-677) acts on the same receptor, but it is not a peptide and is taken by mouth²⁵.

This guide gathers what a physician needs and connects it to our deeper analyses of each molecule. The side-by-side picture of the unapproved compounds is in CJC-1295, ipamorelin and MK-677: the GH and IGF-1 debate.

Mechanism of action: two receptors, one pituitary

GH is released in pulses, under the control of two opposing hypothalamic signals: GHRH stimulates it and somatostatin holds it back. GHRH analogs act on the GHRH receptor of somatotroph cells and specifically stimulate GH secretion¹. That is why they depend on a pituitary that can respond: tesamorelin's label contraindicates it when the hypothalamic-pituitary axis is disrupted¹².

The second pathway was discovered backwards: the drug came first and the hormone later. In 1984, Bowers and colleagues described a synthetic hexapeptide, now known as GHRP-6, that acted on the pituitary to release GH specifically²⁰. Its receptor remained an orphan for years, until in 1999 its natural ligand was isolated from the stomach: ghrelin, an acylated peptide that releases GH²¹. That story is told in GHRP-6, GHRP-2 and ghrelin: when pharmacology discovered a hormone.

The two pathways are not equivalent. The early GHRPs also raised ACTH and cortisol; in conscious pigs, ipamorelin released GH with a potency similar to GHRP-6 and did not raise ACTH or cortisol above what GHRH stimulation produced, even at doses more than 200 times the one giving half its maximal effect on GH, while GHRP-6 and GHRP-2 did raise them²². It is an animal finding, and it is where the word "selective" attached to the molecule comes from; the details are in Ipamorelin: the "selective" GH secretagogue.

The central physiological argument for the whole class is pulsatility. With CJC-1295, which sustains a GHRH stimulus for days, GH kept coming out in pulses: pulse frequency and size did not change, while trough GH between pulses rose 7.5-fold and IGF-1 rose 45%¹⁷. In GH-deficient children treated with sermorelin there was no excessive IGF-1 generation³. An axis that keeps its own regulation is the theoretical difference from exogenous GH; what does not exist is a trial directly comparing the safety of the two approaches in adults.

Sermorelin: history, trials and market withdrawal

Sermorelin, GHRH(1-29) with an amidated end, is the shortest synthetic peptide with the full biological activity of GHRH¹. It held two FDA registrations under the GEREF brand: one approved on December 28, 1990 to assess the pituitary's capacity to secrete GH, and one approved on September 26, 1997 for idiopathic GH deficiency in children with growth failure².

The central pediatric study enrolled 110 prepubertal children with GH deficiency in an open-label multicenter trial with no control group. Mean growth velocity went from 4.1 to 8.0 cm/year at 6 months and 7.2 cm/year at 12 months, with no change in fasting glucose and no excessive IGF-1 generation³. A 1999 review described it as a rapid and relatively specific diagnostic test, with transient facial flushing and injection-site pain as the most common adverse effects, and noted that it had not been compared directly with somatropin and that its effect on final adult height was unknown¹.

In older adults, the evidence is hormonal rather than clinical. In 10 men around 68 years old, two weeks of GHRH(1-29) brought 24-hour GH and IGF-1 to values that did not differ from those of young men⁴. With a single nightly injection for 6 weeks in 11 men aged 64 to 76, nocturnal GH rose but IGF-1 did not change, and neither did body composition⁵.

In 2008 the holder notified the discontinuation of both products, and the FDA withdrew the approvals effective June 18, 2009. In 2013 the agency determined that neither product was withdrawn for reasons of safety or effectiveness². That determination is often confused with a current approval, which does not exist. The full analysis is in Sermorelin: what it is, evidence and regulatory status.

Tesamorelin: the only one with a current approved indication

Tesamorelin is the GH secretagogue with the strongest human evidence. Its label, with initial FDA approval in 2010, indicates it for the reduction of excess abdominal fat in HIV-infected adults with lipodystrophy¹². The first phase 3 trial, published in 2007, randomized 412 patients for 26 weeks: visceral fat fell 15.2% with tesamorelin and rose 5.0% with placebo, triglycerides fell and IGF-1 rose 81%⁶.

The pooled analysis of the two phase 3 trials included 806 patients: at 26 weeks the treatment effect on visceral fat was −15.4% versus placebo, with no significant change in abdominal subcutaneous fat⁷. A 2026 meta-analysis of the controlled trials confirmed the reduction in visceral and trunk fat¹⁴. The effect depends on staying on treatment: in the extension of the first trial, patients switched to placebo reaccumulated visceral fat⁸.

The most interesting finding for internal medicine is in the liver. In 50 patients with HIV, six months of tesamorelin reduced visceral fat and, modestly, liver fat⁹. In a multicenter trial designed for nonalcoholic fatty liver disease in 61 people with HIV, the hepatic fat fraction fell 37% in relative terms versus placebo at 12 months, with no between-group differences in fasting glucose or HbA1c¹⁰. Outside HIV, the main randomized trial enrolled 152 adults aged 55 to 87, healthy or with mild cognitive impairment: over 20 weeks it was associated with a favorable effect on executive function, with more mild adverse events than placebo (68% versus 36%)¹¹.

Europe did not approve it. The application to the European Medicines Agency was withdrawn in June 2012, when its committee had provisionally concluded that it could not be approved: it doubted the fat reduction was clinically meaningful, considered the rise in IGF-1 a major concern because of a possible link to cancer risk, and noted that no long-term safety data were provided¹³. The trials, the limits of the indication and what gets monitored are in Tesamorelin: the GHRH analog that did clear the FDA.

CJC-1295 and ipamorelin: what exists in humans and what is missing

CJC-1295 grew out of a chemical idea: add to a tetrasubstituted GHRH(1-29) a lysine carrying a maleimide group that, in the blood, binds covalently to albumin. In rats, the conjugate was still present in plasma beyond 72 hours¹⁵. In two randomized, placebo-controlled trials in healthy adults aged 21 to 61, a single injection was associated with 2- to 10-fold higher GH for 6 days or more and 1.5- to 3-fold higher IGF-1 for 9 to 11 days, with an estimated half-life of 5.8 to 8.1 days and no serious adverse reactions in those studies¹⁶.

That is where the clinical evidence ends. The phase 2 trial of CJC-1295 in HIV-associated visceral obesity, sponsored by its developer, is listed in the trial registry as terminated in 2006¹⁸, and the molecule never completed phase 3. The name also covers two substances: an anti-doping laboratory found in a preparation of unknown origin, sold as CJC-1295, a 29-amino-acid peptide without the albumin anchor¹⁹, the variant marketed as "no DAC". A 2026 review placed that version at the lowest level of evidence, with no peer-reviewed human studies³³. The anchoring chemistry is explained in CJC-1295 and DAC: the GHRH analog that anchors to albumin.

Ipamorelin has clean human pharmacology and unproven clinical efficacy. In healthy volunteers, each infusion produced a single GH pulse peaking at 40 minutes (0.67 h), with a terminal half-life of 2 hours²³. Its clinical program did not target aging but postoperative ileus, because the ghrelin receptor also has prokinetic effects. Its only randomized efficacy trial, a phase 2 study with 114 analyzed patients after bowel resection, showed no significant difference from placebo: median time to tolerating a solid meal was 25.3 versus 32.6 hours (p = 0.15), although it was well tolerated²⁴.

We found no controlled human trials of CJC-1295 or ipamorelin on body composition, performance, sleep or aging, nor of the two combined. The 2026 reviews agree: favorable results in animal models and scarce rigorous human safety data for the unapproved peptides³³³⁴.

How they compare: sermorelin, tesamorelin, CJC-1295 and ipamorelin

• Sermorelin. GHRH receptor; half-life of minutes. Evidence: open-label pediatric trials and small studies in older adults. Status: approvals in 1990 and 1997, discontinued in 2008, no current approval¹²³⁴.
• Tesamorelin. GHRH receptor; stabilized GHRH(1-44). Evidence: two phase 3 trials with 806 patients, fatty liver trials and one cognition trial. Status: the only one with a current approved indication, limited to HIV with lipodystrophy; not approved in Europe^710111213.
• CJC-1295 (with DAC). GHRH receptor; covalent albumin binding, half-life of days. Evidence: pharmacokinetics and pharmacodynamics in healthy adults. Status: phase 2 terminated, not approved^15161718.
• Ipamorelin. Ghrelin receptor; single GH pulse, 2-hour half-life. Evidence: pharmacology in volunteers and one negative phase 2 trial in postoperative ileus. Status: not approved²²²³²⁴.
• GHRP-6 and ibutamoren (MK-677). Ghrelin receptor; GHRP-6 is the founding molecule of the class and MK-677 is oral and non-peptide, with a 2-year trial in older adults. Status: not approved as a treatment²⁰²⁵.

The comparison teaches a useful rule: the more a molecule has been studied, the narrower and more measured the claims that can be made about it. Tesamorelin has proven benefits in a specific population and a monitoring list written into its label¹²; the compounds with less data do not have fewer risks, just less-known ones.

Safety: IGF-1, glucose and the cancer question

The adverse effects of this class are largely explained by the mechanism itself. Tesamorelin's label, the best document available, reports that at 26 weeks 47% of patients had IGF-1 above 2 standard deviations and 36% above 3; it asks for IGF-1 monitoring during treatment and for considering discontinuation if it stays high, especially when the response is not robust¹².

Glucose is the second alert. With tesamorelin, HbA1c ≥ 6.5% appeared in 5% of treated patients versus 1% on placebo at week 26, with a hazard ratio for diabetes of 3.3, and the label asks for glucose evaluation before and during treatment¹². With ibutamoren for one year in 65 adults aged 60 to 81, fat-free mass rose 1.1 kg with no change in strength or function, but fasting glucose rose about 5 mg/dL and insulin sensitivity fell²⁵. In older adults recovering from hip fracture, an ibutamoren trial was stopped early for a congestive heart failure signal²⁶. Tesamorelin's label adds edema, arthralgia and carpal tunnel syndrome, and injection-site reactions in 25% of treated patients versus 14% on placebo¹².

For exogenous GH itself, the reference is a systematic review in healthy older adults: small body composition changes (−2.1 kg fat, +2.1 kg lean mass) at the cost of more edema, arthralgia, carpal tunnel and gynecomastia, and a trend toward more diabetes; its authors concluded that GH cannot be recommended as an antiaging therapy²⁷. These are not secretagogue data, but they mark the ceiling of what raising the axis can be expected to do in people without deficiency.

Cancer is the open question. IGF-1 stimulates cell proliferation. A 2004 meta-analysis associated high IGF-1 levels with more prostate cancer (OR 1.49) and premenopausal breast cancer (OR 1.65)²⁸, and a collaborative analysis of up to 20 prospective studies found an OR of 1.09 for prostate cancer per standard deviation of IGF-1, with a similar result (OR 1.07) in its Mendelian randomization analysis²⁹. These are associations with the body's own IGF-1, not trials of secretagogues; we found no studies that measured long-term cancer risk with these compounds. Tesamorelin is contraindicated in active malignancy¹², and the same concern weighed on the European assessment¹³.

Doping, quality and what remains unproven

In sport there is no gray zone. The World Anti-Doping Agency's 2026 Prohibited List includes, among the growth hormone-releasing factors in class S2, GHRH and its analogs (with CJC-1295, sermorelin and tesamorelin as examples), GH secretagogues and their mimetics (ibutamoren and ipamorelin) and the GHRPs, including GHRP-6; the whole class is banned at all times, in and out of competition³⁰. Detection has advanced: a validated method to identify GHRH and analogs such as sermorelin, tesamorelin and CJC-1295 in urine was published in 2026³¹.

Quality is the other front. Reviewing ipamorelin for compounding, the FDA flagged possible immunogenicity risks and the complexity of characterizing peptide-related impurities; for CJC-1295 it stated that available clinical data are limited and cited serious adverse events such as increased heart rate and a systemic vasodilatory reaction³². A 2026 review describes uncertainty about the composition of GH-axis peptides circulating outside regulated channels³³, and the preparation of unknown origin sold as CJC-1295, whose analysis identified a 29-amino-acid peptide rather than the albumin-anchored analog of the trials, shows why identity has to be confirmed by analysis¹⁹. How to read that laboratory evidence is summarized in our peptide quality guide.

What remains unproven fits in a few lines:

• That raising GH and IGF-1 with a secretagogue improves hard clinical outcomes in adults without GH deficiency²⁷³³³⁴.
• The long-term safety of any secretagogue outside tesamorelin's approved indication, including cancer risk¹²¹³²⁸.
• The clinical efficacy of CJC-1295 and of ipamorelin, and of the two combined, which has no published human trials¹⁶²⁴³³.
• Whether preserved pulsatility translates into a better safety profile than exogenous GH, which is plausible but has not been compared directly³¹⁷²⁷.