GROWTH HORMONE AXIS / FAQ
Questions From the Literature
Direct, citation-anchored answers to the questions readers most often bring to these three GHRH analog research peptides.
What is sermorelin?
Sermorelin is a synthetic 29-amino-acid peptide that corresponds to the N-terminal 1-29 fragment of human growth hormone-releasing hormone (GHRH). It is the shortest GHRH fragment that retains full agonist activity at the pituitary GHRH receptor. By binding that receptor it stimulates the pituitary to release the body's own GH in a pulsatile, feedback-regulated pattern [1]. It was formerly FDA-approved as Geref for pediatric GH deficiency and withdrawn from the US market in 2008 for commercial, not safety, reasons. It now exists as a 503A Category 1 compounded peptide [3].
What does sermorelin do to the body?
Sermorelin binds GHRH receptors on anterior-pituitary somatotrophs, activating cAMP/PKA signaling that drives GH synthesis and pulsatile release [1]. The released GH then stimulates hepatic IGF-1 production. In a study of healthy older men, twice-daily sermorelin for 14 days raised 24-hour GH and IGF-1 dose-dependently to levels no longer differing significantly from those of young men, without affecting fasting glucose [7]. The effect is upstream of the pituitary, preserving the somatostatin and IGF-1 negative feedback loops that keep levels physiologic, in contrast to exogenous recombinant GH [4].
Does sermorelin work?
For its former approved indication — pediatric growth hormone deficiency — yes: a multicenter trial found once-daily subcutaneous GHRH(1-29) accelerated linear growth from approximately 4.1 cm/year to roughly 7-8 cm/year in the first year, without excessive IGF-1 generation [5]. For adult anti-aging or body-composition uses, the evidence is substantially weaker. A 2008 Annals of Internal Medicine editorial explicitly judged GH-secretagogue use for aging "not yet ready for prime time" based on the available data at that time, and no large controlled adult trial has since changed that assessment [3]. Whether it "works" depends entirely on what it is being used for and in which population.
How long does it take for sermorelin to work?
In pharmacokinetic terms, sermorelin acts quickly but clears rapidly. Intravenous GHRH(1-29) elicited measurable GH release in healthy men at doses as low as 0.25 mcg/kg, with GH remaining elevated approximately 3 hours despite the peptide's rapid plasma clearance [6]. In the pediatric clinical trial, measurable acceleration of linear growth was assessed over a full year of treatment [5]. This site does not advise on dosing schedules or expected timelines for human use.
What is tesamorelin?
Tesamorelin is a synthetic analogue of the full 44-amino-acid human GHRH sequence, bearing a trans-3-hexenoic acid modification at the N-terminus that confers resistance to DPP-IV cleavage and extends plasma stability. It is the only FDA-approved GHRH analog currently on the market. Its approval (NDA 022505, 2010) is for reducing excess abdominal fat in HIV-positive adults with antiretroviral-related lipodystrophy. Like sermorelin, it works by stimulating the pituitary to release endogenous GH rather than supplying exogenous hormone [1][9].
What does tesamorelin do?
In the approved indication, tesamorelin reduces visceral adipose tissue. A 2026 meta-analysis of five RCTs found it reduced visceral fat by a mean of 27.71 cm2, reduced trunk fat by 1.18 kg, reduced hepatic fat by 4.28%, and increased lean mass by 1.42 kg in HIV-positive adults with lipodystrophy [8]. Mechanistically it raises pituitary GH output and hepatic IGF-1, promoting lipolysis preferentially in visceral fat. In healthy men, it raised IGF-1 by 181 ug/L without significantly affecting insulin sensitivity [11].
How does tesamorelin work?
Tesamorelin binds the pituitary GHRH receptor and activates Gs/adenylyl cyclase/cAMP/PKA signaling, stimulating pulsatile GH secretion. The N-terminal hexenoyl modification blocks the DPP-IV enzyme that would otherwise rapidly degrade the peptide at position 1-2, extending its half-life and allowing a once-daily subcutaneous dose to maintain sustained receptor stimulation throughout the day. The downstream GH/IGF-1 cascade then drives lipolysis in visceral adipose tissue, the mechanism underlying its approved visceral-fat reduction effect [1][11].
Will tesamorelin help me lose belly fat?
In HIV-positive adults with antiretroviral-related lipodystrophy — the population studied and the approved indication — yes, the RCT data are robust [8][10]. In general populations without HIV, tesamorelin has no approved indication and no large controlled trial evidence for visceral-fat reduction. Visceral fat also reaccumulates within weeks of discontinuing treatment even in the approved population [12]. This site does not provide dosing recommendations, and use outside the approved indication is off-label.
What is CJC-1295?
CJC-1295 is a synthetic GHRH analog built on the hGRF(1-29) framework with four amino-acid substitutions that increase protease resistance and conformational stability. In its DAC (Drug Affinity Complex) variant, it carries a reactive C-terminal linker that covalently bonds to albumin in the bloodstream, extending the observed plasma half-life to 5.8-8.1 days versus the short half-life of native GHRH [15]. The no-DAC variant ("Modified GRF 1-29") lacks the albumin-binding moiety and is short-acting. CJC-1295 has never been approved for human use; its published human evidence is limited to early pharmacokinetic studies [15][16].
What does CJC-1295 do?
Like sermorelin and tesamorelin, CJC-1295 activates the pituitary GHRH receptor to stimulate endogenous GH release and downstream IGF-1 production. Its distinguishing feature is duration: a single subcutaneous dose of 30-60 mcg/kg in healthy adults produced 2- to 10-fold increases in mean plasma GH lasting 6 or more days, and IGF-1 elevations lasting 9-11 days; after multiple doses IGF-1 remained elevated for up to 28 days [15]. A separate study confirmed that GH pulsatility was preserved despite this sustained elevation [16]. Beyond pharmacokinetics, a proteomic study identified reproducible serum biomarker shifts correlating with IGF-1 activation [14].
Is CJC-1295 safe?
The available human data — two pharmacokinetic studies in healthy adults — did not report serious adverse events at the doses studied, but those studies were short-term and not designed to assess safety comprehensively. CJC-1295 has no approved human indication, was not recommended for compounding at the 2024 FDA advisory committee, and its long-term safety is unknown. Sustained GH/IGF-1 elevation raises theoretical oncologic and metabolic concerns that long-term safety data would need to address [1][15]. This site does not advise on human use.
How much CJC-1295 should I take?
This site does not provide dosing recommendations for any compound. The published human data for CJC-1295 come from pharmacokinetic studies in research settings; dosing in those studies is described as administered, not as advice [15][16]. CJC-1295 has no approved human indication. Common dosing protocols circulating in online communities are not derived from controlled human trials. Individuals interested in growth hormone-axis therapies for any medical purpose should consult a licensed clinician working with approved, regulated options.