Growth Hormone Peptides: A Canadian Research Guide

A landscape view of growth hormone peptides#

Growth hormone peptides are one of the most widely discussed categories in contemporary peptide research, and also one of the most frequently misunderstood. The category groups together compounds that nudge the body's own growth hormone (GH) axis rather than compounds that introduce recombinant human GH directly. That is an important distinction for researchers in Canada, because the regulatory, sourcing, and analytical questions around a secretagogue peptide are quite different from those surrounding a recombinant protein therapeutic.

This guide is a landscape overview. It is not a protocol, a dosing manual, or a how-to. The aim is to help a researcher place each molecule in the broader map before going deeper into any single compound. Where a more focused treatment exists in the Northern Compound library, we point to it.

Two families sit at the centre of the map. The first is the GHRH analogue family: synthetic peptides modelled on growth hormone releasing hormone, the hypothalamic signal that tells the pituitary to release GH. Sermorelin, CJC-1295 (with and without DAC), and tesamorelin are the molecules most often cited in this group. The second is the GH secretagogue or GHRP family: synthetic peptides (and one non-peptide, MK-677) that act on the growth hormone secretagogue receptor, the same receptor that binds the endogenous hormone ghrelin. Ipamorelin, hexarelin, GHRP-2, and GHRP-6 are the canonical GHRPs, and MK-677 is the orally bioavailable outlier.

Understanding where each peptide sits in that two-family map is the single most useful mental model for reading the rest of this guide. Canadian research groups, university labs, and independent researchers looking at body composition, recovery, and endocrine signalling keep returning to these molecules because the underlying biology is well characterised and because the compounds are relatively easy to synthesise to research grade. That accessibility cuts both ways: it also means the supply side is crowded with product of varying provenance.

The two families: GHRH analogues vs GH secretagogues#

The physiological logic behind growth hormone peptides is easier to hold in mind once you separate the two receptor systems they act on.

GHRH analogues bind the growth hormone releasing hormone receptor (GHRHR) on somatotroph cells in the anterior pituitary. The endogenous ligand is a 44 amino acid peptide released from the hypothalamus in a pulsatile pattern. Synthetic analogues shorten the peptide (sermorelin is the first 29 amino acids), stabilise it against enzymatic cleavage (tesamorelin adds a trans-3-hexenoic acid group to the N-terminus), or conjugate it to albumin to extend half-life (CJC-1295 with DAC). All three produce a GH pulse that mirrors the endogenous one in shape, but with a timing and amplitude that reflects the modification.

GH secretagogues, the GHRP class, act on a different receptor: the growth hormone secretagogue receptor (GHSR-1a), which is the ghrelin receptor. Ghrelin itself is a stomach-derived peptide that stimulates both appetite and GH release, and the GHRP class exploits that same pathway. Ipamorelin, hexarelin, GHRP-2, and GHRP-6 are small peptides (five to seven amino acids) that bind GHSR-1a with varying selectivity. MK-677 (ibutamoren) is a non-peptide small molecule that binds the same receptor and happens to be orally active.

The two receptors sit on the same pituitary cells but signal through partially independent intracellular pathways. That is why stacking a GHRH analogue with a GHRP produces a larger GH pulse in research models than either alone: the two signals integrate rather than saturate a single pathway. It is also why the canonical research pairing across the last decade of literature has been a GHRH analogue such as CJC-1295 without DAC together with a GHRP such as ipamorelin.

One more framing point. Neither family introduces growth hormone into the system. Both rely on the pituitary to respond. If the pituitary cannot respond (for any number of reasons that are well outside the scope of a research overview), these peptides cannot compensate for that. The research question they answer is about pulse shape, timing, downstream IGF-1 response, and receptor pharmacology, not about bypassing endogenous biology.

How endogenous GH release works#

Before stepping through individual molecules, it helps to sketch the pathway they plug into.

Rendering diagram...

The hypothalamus releases GHRH in pulses roughly every few hours, with the largest pulses during slow wave sleep. Between pulses, somatostatin from the hypothalamus actively brakes the pituitary. Somatotrophs in the anterior pituitary integrate those two signals and release GH in corresponding pulses. Ghrelin from the stomach adds a third input via GHSR-1a on the same cells. Peripheral GH stimulates IGF-1 production, largely in the liver, and IGF-1 feeds back negatively to the hypothalamus and pituitary.

GHRH analogues drive the green arrow from hypothalamus to pituitary. GHRPs and MK-677 drive the orange arrow from stomach to pituitary. Neither directly affects the somatostatin brake, which is one reason the resulting GH pulse still looks broadly physiological rather than flat and sustained. That is a distinction researchers often care about: a peptide that preserves pulsatility is a different experimental tool from one that drives continuously elevated GH.

GHRH analogues: sermorelin, CJC-1295, tesamorelin#

Sermorelin#

Sermorelin is a 29 amino acid synthetic fragment corresponding to the biologically active N-terminal portion of human GHRH. It was approved decades ago in some jurisdictions for the diagnosis of GH deficiency in paediatric populations and has since been repurposed as a research tool in studies of the somatotropic axis.

The defining characteristic of sermorelin is its short half-life, which is measured in minutes. That produces a clean, brief GH pulse that closely resembles the endogenous signal. For a researcher interested in pulse shape or in short-duration stimulation tests, that brevity is a feature. For a researcher looking at longer downstream effects, it is often why sermorelin gets paired with a longer-acting companion or replaced by a stabilised analogue.

CJC-1295 without DAC#

CJC-1295 without DAC is a GHRH analogue that retains the short half-life of sermorelin but carries amino acid substitutions that increase its binding affinity and resistance to enzymatic degradation. It is often described in the literature as a modified GRF(1-29). Without the drug affinity complex (DAC), it behaves like sermorelin in the sense that it drives a brief pulse, then clears.

CJC-1295 with DAC#

CJC-1295 with DAC is the same GHRH analogue conjugated to a maleimidopropionic acid linker that binds covalently to circulating albumin. That conjugation extends the functional half-life dramatically, to roughly eight days in published studies. Instead of producing a single pulse, it raises baseline GHRH signalling for an extended period.

The DAC and no-DAC versions are often confused in the grey market, and the confusion matters because the two compounds answer different research questions. For a deeper comparison of the two, see the dedicated comparison post at /blog/cjc-1295-dac-vs-no-dac.

Tesamorelin#

Tesamorelin is the most clinically characterised member of the GHRH analogue family. It is a GHRH(1-44) analogue with an N-terminal modification that protects against cleavage by dipeptidyl peptidase IV. Under the brand name Egrifta, it has an approved indication for the reduction of excess abdominal fat in HIV-associated lipodystrophy, supported by randomised controlled trials including the work of Falutz and colleagues published in the New England Journal of Medicine.

For Canadian researchers, this peptide is notable for two reasons. First, it is the GHRH analogue with the deepest human clinical dataset, which makes it a common reference compound. Second, its approved therapeutic context is specifically adipose tissue research rather than general somatotropic axis stimulation, which has shaped much of its published literature. A focused treatment lives at /blog/tesamorelin-deep-dive.

The published pharmacokinetic data on this molecule is also unusually complete. Peak plasma concentrations occur in the first hour after subcutaneous administration, the plasma half-life sits in the 26 to 38 minute range, and downstream IGF-1 rises measurably within days of initiation. That detail matters for researchers designing time-course studies, because it bounds what can reasonably be attributed to the peptide versus to normal circadian variation in the GH axis.

GH secretagogues: ipamorelin, hexarelin, GHRP-2, GHRP-6#

The GHRP class shares a common receptor target but differs meaningfully at the level of selectivity and off-target effects.

Ipamorelin#

Ipamorelin is a pentapeptide designed for selectivity. Unlike earlier GHRPs, it does not meaningfully stimulate cortisol or prolactin release in the doses typically used in research models. That selectivity is why ipamorelin became the default GHRP for research pairings with GHRH analogues: it adds the second-pathway pulse without bringing along the hormonal noise that complicates GHRP-2 or GHRP-6 experiments. A comparison with sermorelin lives at /blog/ipamorelin-vs-sermorelin.

Hexarelin#

Hexarelin is a hexapeptide and one of the most potent GHRPs by weight. It produces large GH pulses in model systems but is less selective than ipamorelin, with measurable effects on cortisol and prolactin. Its profile has also drawn attention in cardiovascular research, because GHSR-1a is expressed in cardiac tissue and hexarelin has shown effects in cardioprotection models that appear partly independent of its GH-releasing activity.

GHRP-2#

GHRP-2 is a second-generation ghrelin receptor agonist often used as a reference compound in endocrinology experiments. It produces reliable and substantial GH release but is less selective than ipamorelin, with documented effects on cortisol, prolactin, and appetite. Its appetite-stimulating effect is real but generally milder than that seen with GHRP-6.

GHRP-6#

GHRP-6 is the archetypal first-generation GHRP and is most often discussed alongside its pronounced appetite-stimulating effect in research models. For researchers studying ghrelin biology specifically, GHRP-6 is a useful tool precisely because it exposes the appetite dimension of GHSR-1a signalling. For researchers interested in clean GH release without the appetite confound, it is usually not the first choice.

MK-677 (ibutamoren): oral, non-peptide, same outcome class#

MK-677 (ibutamoren) is worth treating as its own section because it sits in the GH secretagogue class functionally but differs structurally. MK-677 is not a peptide. It is a spiroindoline small molecule that was developed in the 1990s as an orally bioavailable ghrelin receptor agonist.

Because it is small, oral, and long-acting (with a half-life of roughly 24 hours in human studies), MK-677 produces a fundamentally different GH profile from injectable GHRPs. Rather than a discrete pulse, it produces a sustained elevation of baseline GH and IGF-1 across 24 hours after once-daily dosing in research models. That profile is the reason it remains interesting as a research tool: it separates the pulsatile-versus-tonic question in a way that the injectable peptides cannot.

MK-677 has been studied in a variety of research contexts, including sarcopenia, sleep architecture, and IGF-1 axis investigation. Its oral route and long half-life also make it a different logistical proposition from the injectables, which matters for the design of any Canadian research program.

Why peptides get stacked#

The canonical stack in the growth hormone peptide space is a GHRH analogue plus a GHRP. The most commonly cited pairing is CJC-1295 without DAC plus ipamorelin, often supplied as a pre-blended preparation such as the CJC-1295 and Ipamorelin Blend.

The rationale is mechanistic rather than cultural. GHRH analogues and GHRPs act on different receptors on the same somatotroph cells. Their intracellular signals overlap only partially, so combining them produces a larger GH pulse than either one alone at an equivalent dose. In research models, the combined pulse is not simply additive; it is supra-additive in many published studies, because the GHRP also appears to reduce the somatostatin brake that normally caps a GHRH-driven pulse.

The pairing also has practical logic. A brief-acting GHRH analogue such as sermorelin or CJC-1295 without DAC produces a single clean pulse on a predictable timescale. Adding a selective GHRP to that pulse amplifies it without meaningfully changing the pulse shape, because ipamorelin is itself short-acting and selective. The result is an experimental tool that produces a larger, still-pulsatile GH signal, which is closer to the shape of endogenous biology than continuous stimulation would be.

Stacks beyond that canonical pair appear in the literature but less often. CJC-1295 with DAC plus a GHRP is possible but logistically awkward, because the DAC version circulates for days while the GHRP needs multiple doses per day to hit its effective window. Hexarelin plus a GHRH analogue produces a larger pulse than ipamorelin plus the same GHRH analogue, at the cost of selectivity. GHRP-2 plus a GHRH analogue is sometimes used in endocrinology studies that specifically want the appetite or cortisol read-out alongside GH. For research groups in Canada mapping body composition outcomes rather than mechanism, the ipamorelin combination remains the default, which is why a pre-blended preparation is sold by most serious suppliers.

There is also a stacking question around the growth hormone peptide class and IGF-1 itself. Because GH drives hepatic IGF-1 production, the downstream signal is IGF-1 rather than GH for many research endpoints. That raises the question of whether direct IGF-1 analogues (such as IGF-1 LR3) should ever be combined with peptides in this class, and the short answer from published research is that doing so muddles the read-out. A GH secretagogue stacked with an IGF-1 analogue cannot be cleanly separated from either arm, and researchers who want a clean mechanistic answer tend to run the two arms separately.

For a more detailed treatment of the with-DAC versus no-DAC question that dominates stacking decisions, see /blog/cjc-1295-dac-vs-no-dac.

Pharmacokinetics across the class#

Half-life and pulse shape are where the class genuinely differentiates. The following table summarises the main research parameters; values are drawn from published literature and vary somewhat between studies.

Three patterns are worth pulling out of that table. First, the GHRH analogue family spans an enormous range of half-lives, from minutes (sermorelin, no-DAC CJC-1295, tesamorelin) to days (DAC CJC-1295). That range is the single biggest driver of which experiment a given molecule fits. Second, the GHRP family is relatively uniform in the one-to-two hour range, which is why GHRPs are usually dosed more than once per day in research protocols. Third, MK-677 is the outlier in both half-life and route of administration, and that is precisely why it answers a different research question.

Reconstitution and storage#

Growth hormone peptides are supplied as lyophilised (freeze-dried) powder in vials, typically at a one, two, five, or ten milligram fill. Reconstitution with bacteriostatic water is the standard first step in any research workflow, and the mechanics matter because these peptides are small, relatively stable once reconstituted under the right conditions, and sensitive to heat, agitation, and repeated freeze-thaw.

The practical points are: reconstitute slowly down the side of the vial rather than directly onto the powder, avoid shaking (swirl instead), store reconstituted solution refrigerated at 2-8°C, and plan research work around a use-by window that is typically 14-30 days depending on the specific peptide. Lyophilised powder stored frozen at -20°C or lower is stable for much longer, often years.

A step-by-step treatment with photos and troubleshooting lives at /blog/how-to-reconstitute-peptides. Researchers new to this class should read that first, before worrying about any peptide-specific nuances.

A few points are specific to the growth hormone peptide class. CJC-1295 with DAC, because of the albumin-binding linker, is less tolerant of aggressive handling during reconstitution than the simpler GHRH analogues. Tesamorelin is often supplied with a specific recommended diluent volume that produces a standard research concentration, and deviating from that volume for convenience tends to produce confusion in recordkeeping. Ipamorelin, GHRP-2, and GHRP-6 are relatively forgiving in reconstitution but all share the same freeze-thaw sensitivity once in solution. MK-677 is a different case entirely, because it is an oral small molecule, typically supplied as a powder or solution that does not involve reconstitution with bacteriostatic water.

Calibration is the other recurring issue. A one milligram vial reconstituted in one millilitre yields a one milligram per millilitre solution. Reconstituted in two millilitres, it yields half that concentration. Research groups working across multiple peptides with different vial fills routinely make volumetric mistakes at this step, and the resulting dosing errors propagate through the entire study. Writing the reconstitution volume, the resulting concentration, and the calculated volume per research dose directly on the vial label (or on a tag attached to it) removes an entire category of avoidable error from the workflow.

Research applications#

The published literature on growth hormone peptides spans several distinct research questions, and it is useful to separate them explicitly.

GH and IGF-1 axis investigation is the foundational use. Sermorelin, CJC-1295, and tesamorelin have all been used in human and animal studies to characterise GHRH receptor pharmacology, measure downstream IGF-1 response, and map pulse dynamics. Ipamorelin, GHRP-2, and hexarelin have played parallel roles for the GHSR-1a receptor.

Body composition research, particularly in animal models, is the second major area. Tesamorelin's clinical data on visceral adipose tissue is the deepest, but the broader class has been examined in preclinical body composition studies looking at lean mass, fat mass, and adiposity distribution.

Recovery and tissue repair research sits alongside the body composition work. GH and IGF-1 are central to protein synthesis and tissue remodelling, so peptides that modulate their signalling are of interest in musculoskeletal models. These lines of research typically complement, rather than replace, work with direct tissue-repair peptides.

Sleep architecture and neuroendocrinology form a smaller but active area. MK-677 in particular has been studied for its effects on slow wave sleep, which is interesting because slow wave sleep is also when the largest endogenous GH pulses occur.

Finally, ageing and sarcopenia research draws on the entire class. The rationale is that somatotropic axis signalling declines with age, and the peptides in this family offer experimental tools for examining that decline without the confounds of recombinant GH administration.

None of this constitutes a therapeutic recommendation. These are research applications, and the compounds discussed are research chemicals in Canada.

It is also worth noting what growth hormone peptides are not well-suited to research. They are not a tool for studying pituitary function in a somatotroph that cannot respond, because the entire mechanism depends on the pituitary being able to release GH. They are not a tool for delivering a supraphysiological GH signal, because the resulting pulses, while larger than baseline, remain pulsatile and capped by the somatostatin brake. And they are not a tool for studying GH receptor pharmacology downstream of the pituitary, because they act upstream. Researchers looking at peripheral GH receptor biology typically use recombinant GH or IGF-1 analogues instead.

Canadian research in this space also increasingly overlaps with the literature on sarcopenia and frailty in older adults. Several recent reviews from Canadian geriatric medicine groups have highlighted the somatotropic axis as a target for investigation in age-related muscle loss, and growth hormone peptides offer an experimental handle on that axis without the confounds of recombinant GH. Whether that line of research matures into something therapeutically useful is an open question, but the volume of Canadian preclinical work in the area has grown meaningfully over the past several years.

Canadian supplier landscape#

Canada has a distinct research peptide supply environment. Domestic suppliers ship within the country without cross-border complications, a small number of them publish third-party certificates of analysis for every batch, and a still smaller number do that consistently for the growth hormone peptide class specifically.

That last point matters because the growth hormone peptide category is one of the most heavily counterfeited corners of the grey market internationally. The molecules are well known, the synthesis routes are widely documented, and the price points are high enough to attract both legitimate manufacturers and less scrupulous ones. A researcher cannot tell the difference between a ninety-eight percent pure CJC-1295 and a sixty percent pure CJC-1295 by visual inspection of the vial, and the functional consequences of that gap in research are real.

A credible Canadian supplier for this class should, at minimum, publish a third-party mass spectrometry and HPLC certificate of analysis for every batch, match the batch number on the COA to the batch number on the vial, and ship with appropriate cold-chain handling. CJC-1295 with DAC, tesamorelin, and the other members of the class should all carry that documentation, with no exceptions for specific molecules.

Price is a useful but noisy signal. A growth hormone peptide priced far below the typical Canadian range is more likely to be underfilled or impure than it is to reflect a better supply chain. A peptide priced dramatically above the range does not automatically indicate higher quality either. Within a reasonable Canadian price band, the differentiator is analytical documentation and logistics, not the headline dollar figure.

Lynx Labs operates domestically in Canada and publishes third-party COAs for the full growth hormone peptide range. They stock all members of the family discussed in this guide, including a pre-blended CJC-1295 plus ipamorelin preparation that many research groups prefer to compounding the two components separately. That combination of domestic shipping, batch-level analytical documentation, and full class coverage is the short version of what Canadian researchers should be looking for in any supplier.

For a broader treatment of Canadian supply across peptide classes, Health Canada's published guidance on research chemicals provides helpful regulatory context, and the University Health Network (UHN) in Toronto as well as the University of Toronto's endocrinology research groups have published research that references the broader peptide supply environment in Canada. McGill University in Montreal, where much of the early tesamorelin clinical work was conducted under Julian Falutz and colleagues, also remains a notable Canadian reference point for growth hormone peptide research at a clinical scale.

Common pitfalls#

A handful of recurring mistakes show up in the growth hormone peptide space often enough to be worth flagging explicitly.

The first is the CJC-1295 with DAC versus without DAC confusion. The two compounds share most of their name but differ fundamentally in half-life and therefore in dosing cadence. Supplied side by side under almost identical labels in some stores, they are easy to mix up, and a protocol designed for no-DAC dosed as DAC (or vice versa) produces a very different GH profile from the one intended. Read the label, read the COA, and confirm the molecular weight.

The second is timing error. GHRH analogues and GHRPs both work best in research models when administered away from a meal containing carbohydrate or fat, because a post-prandial insulin or fatty acid spike blunts the GH pulse. Protocols that administer these peptides in the middle of a carbohydrate-rich feed window tend to under-observe the effect they are looking for, then (incorrectly) blame the peptide.

The third is buying from sources without a batch-specific COA. The grey market for growth hormone peptides is particularly noisy, and the absence of a batch-matched third-party certificate is the clearest available signal that a researcher cannot verify what is in the vial. Domestic Canadian suppliers that publish COAs consistently, Lynx Labs among them, remove that variable from the research.

The fourth is over-interpreting short-term IGF-1 numbers. IGF-1 integrates over days, and a single measurement can swing with meals, sleep, and acute stress. Research designs that rely on a single pre-post IGF-1 comparison rather than a time series frequently reach conclusions the data do not support.

The fifth is freeze-thaw damage. Reconstituted growth hormone peptides tolerate refrigeration well but tolerate repeated freezing and thawing poorly. A vial that has been frozen, thawed, frozen again, and thawed again is a vial producing unreliable results, even if the lyophilised source material was analytically clean.

The sixth is treating the growth hormone peptide class as interchangeable with recombinant human growth hormone. They are not. Recombinant GH is itself the hormone, administered directly, with pharmacokinetics determined by its formulation rather than by any upstream signalling. Growth hormone peptides produce a GH pulse through the researcher's own pituitary, capped by endogenous feedback mechanisms such as somatostatin and negative feedback from IGF-1. A research design that conflates the two categories will not produce coherent conclusions.

The seventh, and the most avoidable, is incomplete labelling of the research compound in the laboratory notebook. The CJC-1295 with versus without DAC confusion is the most common version of this, but it extends to the GHRP family as well: a vial of GHRP-2 and a vial of GHRP-6 look identical, handle identically, and will produce meaningfully different results in the same experiment. Labelling practice is one of the cheapest quality controls available to a research group, and one of the most frequently neglected.