How do GH secretagogues differ from injecting growth hormone directly?

Injecting recombinant growth hormone floods the body with the hormone itself. Secretagogues work upstream by causing the pituitary to release more of its own stored GH in pulses that remain subject to normal negative feedback. This preserves more of the natural pattern of secretion, though whether that translates into a clinically different safety profile depends on the specific compound, dose, and setting.

Is ipamorelin approved by the FDA?

No. Ipamorelin was developed by Novo Nordisk in the late 1990s and early 2000s and was evaluated in early clinical trials for postoperative ileus and muscle wasting. The program was discontinued, and ipamorelin has never received FDA approval for any indication. It is available only as a research peptide.

What is tesamorelin approved to treat?

Tesamorelin, sold as Egrifta, is approved by the FDA for the reduction of excess abdominal fat in HIV-infected adult patients with lipodystrophy. That is the only approved indication. Research in other contexts (NAFLD, cognition) has been conducted but has not led to additional approved uses.

Are GH secretagogues banned by WADA?

Yes. The World Anti-Doping Agency prohibits growth hormone secretagogues at all times under section S2 of its Prohibited List. This includes both GHRH analogs like tesamorelin and ghrelin mimetics like ipamorelin. Athletes subject to WADA rules face anti-doping consequences for using these compounds.

Growth Hormone Secretagogues: Ipamorelin, Tesamorelin, and the GH Axis

Published: April 10, 2026•Updated: April 10, 2026

Research use only. This article discusses compounds that include approved medications, investigational drugs, and research peptides. Material sold for research is not cleared for human administration and is not a substitute for medical advice.

Growth hormone secretagogues are compounds that cause the pituitary gland to release more of its own stored growth hormone. Instead of administering growth hormone directly, they work upstream by activating the natural signaling pathways that control its release. This article covers how the growth hormone axis actually works, the two main receptor families drug developers have targeted, and what the published research shows about the best-known compounds in each family.

The growth hormone axis in brief

Growth hormone (GH) is a 191 amino acid protein secreted by the anterior pituitary gland in pulses throughout the day, with the largest pulses typically occurring during deep sleep. Its release is controlled by two competing signals from the hypothalamus: growth hormone releasing hormone (GHRH) stimulates release, and somatostatin inhibits it. A third signal, ghrelin, coming from the stomach, also stimulates release through a separate receptor.

When GH reaches peripheral tissues, it stimulates production of insulin-like growth factor 1 (IGF-1), mostly from the liver. IGF-1 is responsible for many of the downstream effects of GH and also provides negative feedback to the hypothalamus and pituitary to dampen further GH release. This feedback loop is why simply flooding the system with exogenous GH is different, physiologically, from stimulating the body to release its own GH in normal pulses.

Two pathways, two drug classes

Drug developers have targeted two distinct receptors in the GH axis, leading to two broad classes of secretagogues with different pharmacology.

GHRH analogs

These compounds mimic the hypothalamic hormone GHRH and bind the GHRH receptor on pituitary somatotrophs. Tesamorelin, marketed as Egrifta, is an FDA-approved GHRH analog used in HIV-associated lipodystrophy. Sermorelin is an older GHRH analog with a shorter history of use.

Ghrelin mimetics (GHRPs)

These compounds mimic the stomach-derived hormone ghrelin and bind the growth hormone secretagogue receptor (GHSR-1a). Ipamorelin is a well-known example of a selective ghrelin mimetic that was developed by Novo Nordisk but never reached approval. Other members of this family include GHRP-2, GHRP-6, and hexarelin.

The two pathways are complementary in normal physiology. GHRH and ghrelin each trigger GH release through separate receptors, and combining the two has been shown in some studies to produce larger GH pulses than either alone.

Tesamorelin: the approved example

Tesamorelin is a synthetic analog of the first 44 amino acids of human GHRH with a trans-3-hexenoic acid group attached to the N-terminus that protects it from rapid degradation. It was developed by the Canadian biotech Theratechnologies and approved by the FDA in 2010 as Egrifta for the reduction of excess abdominal fat in HIV-infected patients with lipodystrophy.

Two phase 3 trials in HIV-infected adults with excess abdominal fat, published in NEJM in 2007 and AIDS in 2010, reported significant reductions in visceral adipose tissue on CT imaging compared with placebo after 26 weeks of daily injection. These trials established the approved indication. Subsequent smaller research has examined tesamorelin in other contexts, including nonalcoholic fatty liver disease and mild cognitive impairment, but those uses are not FDA approved.

Ipamorelin: the research peptide

Ipamorelin is a synthetic pentapeptide that binds the ghrelin receptor and triggers GH release. It was developed by Novo Nordisk in the late 1990s and early 2000s as a selective secretagogue with minimal effects on cortisol, prolactin, and other pituitary hormones compared with earlier GHRPs like hexarelin. Initial characterization was published by Raun and colleagues in the European Journal of Endocrinology in 1998.

Novo Nordisk advanced ipamorelin into early clinical trials for postoperative ileus and muscle wasting conditions but did not bring it to approval. The program was discontinued, and ipamorelin remained available only as a research peptide. It has no FDA-approved prescribing information, and material sold under the ipamorelin name is intended strictly for laboratory use.

Where the research actually points

The published clinical evidence base for secretagogues differs dramatically across specific compounds, and this difference is worth understanding.

•Tesamorelin has phase 3 clinical trial evidence in a narrow approved indication and is a legitimate prescription therapy for HIV-associated lipodystrophy
•Ipamorelin has early clinical trial data from Novo Nordisk's program in postoperative ileus but never advanced to phase 3 approval and has no established efficacy for the uses commonly discussed in online communities
•Older ghrelin mimetics like GHRP-2, GHRP-6, and hexarelin have varying amounts of research but are generally less selective than ipamorelin and are not approved
•Oral ghrelin mimetics like ibutamoren (MK-677) have their own distinct profile and are separate from the injectable peptides discussed here

Safety, feedback, and regulatory context

Because GH secretagogues trigger release of endogenous GH rather than administering GH itself, the resulting GH pulses remain subject to physiologic feedback from IGF-1 and somatostatin. This is often cited as a theoretical advantage over direct GH administration, because it preserves some of the natural pulsatile pattern. Whether that translates into a meaningfully different clinical safety profile is still an open question and depends on the specific compound and dose.

Known concerns with GH axis activation include glucose intolerance, fluid retention, joint discomfort, and theoretical concerns around effects on insulin signaling. The Egrifta prescribing information discusses these in the context of its approved use.

From an anti-doping standpoint, the World Anti-Doping Agency prohibits growth hormone secretagogues at all times under section S2 of its Prohibited List. This applies to both GHRH analogs and ghrelin mimetics, including both approved drugs used off-label and unapproved research peptides.