Sermorelin + Ipamorelin: The Unmodified GHRH Fragment Paired With a Selective Secretagogue

Pairing the untouched native GHRH fragment with a selective pentapeptide agonist at the ghrelin receptor, this sermorelin and ipamorelin blend is co-lyophilized at a 1:1 ratio. What sets it apart is an absence on the GHRH side: sermorelin is human GHRH (1-29) amide with nothing substituted, no acyl cap and no albumin-binding linker. This is the reference molecule from which the modified analogues were developed, and its brief reported persistence — around ten to twenty minutes according to published pharmacokinetics — counts as a characteristic rather than a shortcoming. When a study concerns pulse structure and somatotroph responsiveness instead of prolonged exposure, the native fragment models the situation more faithfully.

Our sermorelin and ipamorelin preparation is a 1:1 co-lyophilized powder in 10 mg (5 mg/5 mg) and 20 mg (10 mg/10 mg) vials, within the growth hormone blends range.

Where each component comes from

GRF (1-29) amide is sermorelin: the opening 29 residues of the 44-residue human growth hormone releasing hormone, ending in an amide. Early-1980s truncation work showed this fragment retains the intact hormone's full capacity to activate the receptor, making it the obvious foundation for every GHRH analogue that followed. Leaving the sequence unmodified means the Tyr1-Ala2 bond is still a target for dipeptidyl peptidase-4, and clearance is quick in proportion.

For a research peptide, sermorelin also has an unusual regulatory past: it was once an approved prescription product in the United States, applied in paediatric growth hormone deficiency and as a pituitary-function diagnostic, and it was withdrawn in 2008 on commercial rather than safety grounds. Our sermorelin explainer has the detail, and the comparison of CJC-1295 with sermorelin works through how it differs from the substituted 29-residue analogue.

Ipamorelin came out of Novo Nordisk's programme in the 1990s: a synthetic pentapeptide constructed around aminoisobutyric acid and D-2-naphthylalanine. Preclinical and human pharmacology publications described growth hormone release unaccompanied by the rises in cortisol, ACTH and prolactin that GHRP-2, GHRP-6 and hexarelin produce — the selectivity that keeps it in blends today. The structure is covered in our ipamorelin explainer.

Why the two are combined

Each peptide reaches the same pituitary somatotroph, but through a different receptor using a different second messenger. Signalling at the GHRH receptor is Gs-coupled, so agonism lifts cAMP and switches on protein kinase A. Signalling at the ghrelin receptor is Gq-coupled, so agonism engages phospholipase C, produces inositol trisphosphate and raises intracellular calcium. Studies combining a GHRH-class compound with a GHRP-class secretagogue have repeatedly described a bigger secretory response than either produces alone, and activity at GHS-R1a has further been described as easing the inhibitory influence of somatostatin, which lets the GHRH-driven response run fuller.

What gives this blend its practical character is how briefly sermorelin persists. With both components clearing rapidly, the exposure profile takes the form of a sharp pulse instead of a sustained elevation — nearer the body's own secretory pattern than a long-acting analogue can manage, and correspondingly better matched to questions about pulse amplitude, receptor responsiveness and desensitisation kinetics. Where a study calls for sustained exposure, an acyl-capped or albumin-binding GHRH analogue is the more appropriate tool.

A note on the arithmetic: equal masses are not equal moles. Given 3,357.93 against 711.85 g/mol, five milligrams of sermorelin amounts to about 1.49 µmol while five milligrams of ipamorelin amounts to about 7.02 µmol — roughly 4.7 molar equivalents of the pentapeptide for each of the GHRH fragment. Co-lyophilizing also locks that proportion in place; changing it means buying separate Sermorelin and Ipamorelin vials, a trade-off discussed in our comparison of blends and single vials.

What has been studied

Pituitary function and diagnostic pharmacology

Diagnostics account for the largest body of human data on sermorelin: it served to test somatotroph responsiveness and to separate hypothalamic from pituitary causes of growth hormone deficiency. Those studies describe the human GHRH receptor response in considerable detail.

Paediatric growth hormone deficiency

The clinical work behind the former approved product looked at growth velocity in children whose deficiency responded to GHRH. That evidence concerns a prescription medicine given under medical supervision, not research-grade material.

Combined GHRH and secretagogue pharmacology

From the 1990s onward a separate literature gave GHRH or sermorelin together with a GHRP-class secretagogue and reported pituitary synergy. Because much of that work used sermorelin itself, it bears more directly on this blend than on blends built from engineered analogues.

Sleep and ageing models

Growth hormone secretion being linked to deep slow-wave sleep, several studies have tested GHRH-class compounds in sleep-architecture models, including in older adults whose secretory amplitude has declined. These findings are exploratory.

What has not been established

This co-formulated product has never been studied in controlled trials, and no data show that a 1:1 mass ratio is optimal for any research question. The composition is a formulation convention, not an evidence-based specification.

Presentations available

Both sizes are co-lyophilized in one vial, so a single reconstitution yields a solution holding both peptides at the stated ratio. Shorter series suit the 10 mg (5 mg/5 mg) vial, while the 20 mg (10 mg/10 mg) vial is more economical where a longer study should stay on one lot. Every lot comes with a certificate reporting purity per component at ≥99% by HPLC.

Reconstitution and storage at the bench

Treat the blend as a single material when reconstituting. Use bacteriostatic water where the vial will be drawn from more than once, and sterile water where a preservative would disturb the assay. Send the solvent down the vial wall and swirl rather than shake.

The 1:1 ratio makes the arithmetic symmetrical. Taking a 10 mg (5/5) vial up in 2 mL of diluent gives 5 mg/mL in total, meaning 2.5 mg/mL of each peptide, so 0.1 mL — ten units on a U-100 syringe — carries 250 micrograms of the GHRH fragment and 250 mcg of ipamorelin. A 20 mg (10/10) vial made up with 4 mL gives identical per-volume figures. The method is set out in our reconstitution guide.

A handling point applies to sermorelin specifically: its sequence carries a methionine at position 27, an oxidation-prone residue that the CJC-1295 family substitutes with leucine. Native sermorelin keeps it, so shielding the material from light, air and warm storage matters more than it does for the engineered analogues. Hold lyophilized vials at −20 °C and reconstituted solution at 2–8 °C through the study window, aliquoting and freezing for longer programmes. General practice is in how to store peptides.

Purity and reading a blend certificate

A sound two-component certificate is marked by three things. Purity belongs to each peptide separately rather than to a single combined figure. Mass spectrometry should verify both expected masses, 3,357.93 g/mol and 711.85 g/mol; with sermorelin in particular, an observed value 16 Da above expectation points to oxidation at the methionine and deserves a query. And the HPLC trace should show two resolved peaks whose relative areas fit the labelled 1:1 mass ratio.

Regulatory position

Sermorelin was previously an approved prescription product in the United States and was taken off the market in 2008; no approved product exists now, and research-grade material never was that product and inherits none of its approvals. Ipamorelin holds no marketing authorisation in any jurisdiction. Anti-doping rules prohibit GHRH analogues and growth hormone secretagogues in sport.

Related blends and further reading

Hold ipamorelin constant and swap the GHRH-side partner and you get CJC-1295 (No DAC) + Ipamorelin, with four residues substituted to resist degradation, or Tesamorelin + Ipamorelin, which pairs it with the complete 44-residue sequence bearing an N-terminal acyl cap.