Hormonal & Endocrine Peptides

Hormonal and endocrine peptides primarily target the growth hormone (GH) axis — a critical regulatory system that governs body composition, tissue repair, sleep quality, and metabolic health. GH secretion from the anterior pituitary declines with age (a phenomenon called somatopause), and this category contains the peptide tools developed to partially restore youthful GH pulsatility without the risks associated with exogenous HGH administration.

The growth hormone axis operates through two complementary receptor pathways. The first is the GHRH receptor, stimulated by growth hormone-releasing hormone (GHRH) from the hypothalamus. The second is the GHS-R (growth hormone secretagogue receptor), stimulated by ghrelin, the hunger hormone. Optimal GH release requires activation of both pathways simultaneously — and this is the rationale behind the GHRH + GHS-R peptide stacking strategy.

CJC-1295 is a modified GHRH analogue with an extended half-life (7-10 days with DAC formulation). It provides sustained stimulation of the GHRH receptor to maintain elevated GH and IGF-1 levels between injections. Ipamorelin is widely considered the cleanest GHS-R agonist — it produces selective GH pulses with minimal cortisol, prolactin, or cortisol elevation compared to first-generation GHRPs. The CJC-1295 + Ipamorelin combination is one of the most widely researched GH peptide protocols.

Sermorelin is a truncated GHRH analogue containing the first 29 amino acids of natural GHRH. It is shorter-acting than CJC-1295, requiring more frequent dosing but producing a more physiological GH pattern. Some clinicians prefer Sermorelin for older patients due to its more gentle profile. MK-677 (Ibutamoren) is an oral, non-peptide GHS-R agonist that provides 24-hour GH elevation through a convenient oral route — the only GH secretagogue that does not require injection.

In the UK, no GH secretagogue peptides are licensed for cosmetic or performance use. Sermorelin has been used off-label by private clinics for age-related GH deficiency. MK-677 is sold as a research chemical. The MHRA would consider these medicinal products if marketed for GH-related indications. True GH deficiency should be diagnosed via ITT or GHRH-arginine testing and treated with licensed recombinant HGH (Genotropin, Norditropin) under endocrinologist supervision.