Sermorelin (GHRH 1-29): 5mg vs 10mg Research Guide
By UK Peptide Lab Research Team•15 September 2026•7 min read
Key Takeaways
- The 5mg and 10mg vials contain the identical 29-residue peptide — the 10mg is the higher-mass format, not a stronger or purer material.
- Each vial size is its own batch with its own published certificate of analysis; purity figures are not inherited between sizes.
- At an identical fill volume a 10mg vial reaches twice the concentration of a 5mg vial, so reconstitution volumes must be scaled rather than carried over.
- Sermorelin's methionine at position 27 is oxidation-prone, and the longer working life of a larger vial makes aliquoting into single-use volumes matter more.
- Sermorelin was once the licensed diagnostic Geref, but no product holds a marketing authorisation today; it is supplied strictly for in-vitro research.
What is Sermorelin?
Sermorelin, catalogued as GRF (1-29)-NH₂ or GHRH (1-29), is a synthetic 29-residue peptide amide corresponding to the first 29 amino acids of human growth-hormone-releasing hormone. Its one-letter sequence is YADAIFTNSYRKVLGQLSARKLLQDIMSR-NH₂, its molecular weight is 3357.9 g/mol and its CAS number is 86168-78-7. It is the shortest fragment of the native 44-residue hormone that retains full biological activity, and it binds the GHRH receptor on anterior pituitary somatotrophs to stimulate release of endogenous growth hormone. Sermorelin is unusual in this catalogue for having been a licensed medicine: as Geref it served as a provocative diagnostic agent for assessing pituitary growth hormone reserve and was studied in children with idiopathic growth hormone deficiency, a clinical literature reviewed in detail by Prakash and Goa (BioDrugs, 1999). The product was withdrawn from the market for commercial reasons rather than any safety finding, and no sermorelin product holds a marketing authorisation anywhere today. UK Peptide Lab supplies both Sermorelin 5mg and Sermorelin 10mg as lyophilised powder for in-vitro laboratory research use only.
GHRH (1-29): Chemistry and the Analogue Family
Native human GHRH is 44 residues long; the 1-29 fragment with a C-terminal amide retains the receptor activity of the whole hormone, which is why GHRH (1-29) became the standard scaffold for analogue development. The original characterisation work is the tumour-derived GHRF papers — Guillemin and colleagues isolated a growth hormone-releasing factor from a pancreatic tumour in Science in 1982, and Rivier, Spiess, Thorner and Vale reported the 44-residue structure in Nature the same year. Modified GRF (1-29) and the CJC-1295 family are substitution products of exactly this 29-residue backbone, which makes unmodified sermorelin the natural reference compound for the whole family. The unmodified sequence carries known chemical liabilities that the analogues were designed to close: an N-terminal Tyr-Ala motif open to dipeptidyl peptidase-4 cleavage, an asparagine at position 8 prone to deamidation, and — the one that matters most day to day in the laboratory — a methionine at position 27 prone to oxidation.
Sermorelin 5mg vs 10mg: Same Molecule, Different Vial Content
The 5mg and 10mg presentations contain the identical peptide. Same sequence, same molecular weight, same receptor pharmacology, same lyophilised powder — the 10mg vial is simply the higher-mass format, holding double the lyophilised mass in the same single-vial glass format, for protocols that call for a larger total peptide mass. There is deliberately no purity or quality difference between the sizes. Each vial size is its own batch, with its own third-party certificate of analysis: the current 5mg batch is UKPL-780, verified at 99.3% purity by RP-HPLC, and the 10mg batch carries its own batch number and its own published certificate rather than inheriting the 5mg's figures. The practical consequences are arithmetic and logistical rather than chemical. At an identical fill volume, a 10mg vial reaches twice the concentration of a 5mg vial, so reconstitution volumes must be scaled rather than carried over. One batch and one certificate cover twice as much work, which is the batch-continuity argument, and per-vial costs — vial, stopper, lyophilisation, third-party assay — fall across twice the milligrams, which is the cost-per-milligram argument. The counter-argument is exposure, and it is specific to this molecule: the methionine at position 27 is oxidation-prone, and a vial holding twice the mass is typically consumed over a longer working life, accumulating more stopper penetrations, headspace air contact and light exposure on a single reconstituted stock. Aliquoting into single-use volumes at the point of reconstitution resolves that.
Handling: The Methionine-27 Problem
Oxidation of Met27 is the degradation route to design against with sermorelin. In lyophilised form the residue is protected; in dilute solution it is not, and the rate of methionine sulfoxide formation tracks air exposure, light and time at room temperature. A 10mg vial concentrates this problem simply because its stock is typically in use for longer. The standard countermeasure is to reconstitute, then immediately draw single-use aliquots into separate vessels and freeze them at -20°C, so that each withdrawal takes only what it needs from a stock that has seen minimal oxidative history. Keep vials tightly sealed with minimal headspace, protect from light, and never store the solution in contact with oxidising agents.
Reconstitution and Storage
Allow the vial and the bacteriostatic water to reach room temperature, then sterilise both stoppers with an alcohol swab. Inject the diluent slowly down the inner glass wall — never directly onto the lyophilised cake — and swirl gently in a slow circular motion until fully dissolved. Never shake or vortex: a 29-residue peptide is shear-sensitive and agitation reduces recovery of intact material. The solution should be clear and colourless. Store lyophilised vials at -20°C, protected from light and moisture, for up to 24 months; hold the reconstituted solution at 2-8°C and use within approximately 4 weeks, or freeze single-use aliquots for longer storage and avoid repeated freeze-thaw cycles. See the peptide storage guide for the general principles.
Research Applications and the Honest Boundaries
Sermorelin is used in neuroendocrine research as the reference GHRH (1-29) receptor agonist: somatotroph signalling and pituitary growth hormone release models, GHRH receptor pharmacology, and comparative work in which stabilised analogues are benchmarked against the native fragment they derive from. Its distinctive asset is a genuine human clinical literature from the Geref diagnostic era (Prakash and Goa, BioDrugs, 1999), and Walker (Clin Interv Aging, 2006) discusses the same pharmacology as a route into studying the GHRH axis in adult-onset growth hormone insufficiency. The honest boundaries: the Walker paper is a perspective article rather than a trial report, the Geref licence lapsed for commercial reasons and no sermorelin product is approved today, and applications beyond the characterised diagnostic pharmacology remain unestablished. Material supplied here is for in-vitro laboratory research only.
Sourcing in the UK
UK Peptide Lab supplies research-grade Sermorelin 5mg and Sermorelin 10mg as lyophilised powder with full third-party HPLC documentation published on each product page. Same-day UK dispatch on orders placed before 2pm GMT, free Royal Mail Tracked shipping over £45. For in-vitro laboratory research use only, not for human consumption.
Related Products
Disclaimer: This article is for research and educational purposes only. All information provided is not intended as medical advice. UK Peptide Lab products are not for human consumption and are sold strictly for laboratory research use only.
Frequently Asked Questions
Is the Sermorelin 10mg vial the same peptide as the 5mg vial?
Yes. Both vials contain the identical 29-residue GHRH (1-29) amide, sequence YADAIFTNSYRKVLGQLSARKLLQDIMSR-NH₂ at 3357.9 g/mol. The 10mg vial is the higher-mass presentation of the same compound, not a different sequence or a stronger material. Each vial size carries its own batch and its own published certificate of analysis.
Which vial size should I choose for research?
Choose the 5mg vial for pilot work and short protocols, and the 10mg vial when a protocol calls for a larger total peptide mass, where batch continuity under one certificate of analysis and cost per milligram matter. The 10mg vial's longer in-use window makes aliquoting at reconstitution more important, since the methionine at position 27 is oxidation-prone.
How is a reconstituted Sermorelin vial stored?
Store lyophilised vials at -20°C for up to 24 months. Once reconstituted with bacteriostatic water, hold the solution at 2-8°C and use within approximately 4 weeks, or draw single-use aliquots immediately and freeze them at -20°C, avoiding repeated freeze-thaw cycles. Keep the vial tightly sealed with minimal headspace and protected from light.
References
- [1] Sermorelin: a review of its use in the diagnosis and treatment of children with idiopathic growth hormone deficiency (Prakash and Goa). BioDrugs (1999). View →
- [2] Sermorelin: a better approach to management of adult-onset growth hormone insufficiency? (Walker). Clinical Interventions in Aging (2006). View →
- [3] Growth hormone-releasing factor from a human pancreatic tumor that caused acromegaly (Guillemin et al.). Science (1982). View →
- [4] Characterization of a growth hormone-releasing factor from a human pancreatic islet tumour (Rivier, Spiess, Thorner and Vale). Nature (1982). View →