Sermorelin is the first 29 amino acids of the 44-amino-acid GHRH molecule. It represents the minimum fragment that retains full biological activity at the GHRH receptor — everything after position 29 is dispensable for receptor binding and GH release stimulation.¹

This economy makes Sermorelin the cleanest GHRH tool: no extra sequences with potential off-target effects, just the essential receptor-binding domain.

Sermorelin's former FDA approval (Geref, for GH deficiency assessment in children) gives it a clinical evidence base unusual for research peptides. The GHRH stimulation test — injecting Sermorelin and measuring the GH response — was used to distinguish pituitary GH deficiency from hypothalamic GH deficiency. A robust GH response to Sermorelin indicated the pituitary was functional but not receiving adequate GHRH from the hypothalamus.²

This clinical application validated Sermorelin as a reliable GH releaser in humans — not just animal models.

Sermorelin's value in the current OSYRIS catalog is primarily comparative: - vs Tesamorelin: Sermorelin is shorter-acting (no DPP-IV protection) and produces briefer GH pulses. Tesamorelin is DPP-IV resistant with longer duration. - vs CJC-1295 (no DAC): CJC-1295 has additional modifications beyond DPP-IV resistance. Sermorelin is the unmodified reference. - vs Ipamorelin: Different receptor entirely (GHRH-R vs GHS-R1a). Complementary, not competitive.

Sermorelin is the simplest, most well-characterized GHRH analog — the baseline against which all modifications are compared.³

DPP-IV rapidly degrades Sermorelin in vivo, giving it a very short half-life (~10-20 minutes). This limits sustained GH stimulation but is actually advantageous for pulsatile GH research where short-duration bursts are desired. For sustained stimulation, Tesamorelin or CJC-1295 are preferred.