Source comparison
Receptor Pharmacology: GHRHR vs GHS-R1a
Sermorelin (GHRHR agonist): Sermorelin is a 29-amino acid analogue of endogenous GHRH (1–44), retaining the N-terminal sequence required for GHRHR binding and activation. GHRHR is a Gs-coupled GPCR expressed almost exclusively in pituitary somatotrophs in the
This comparison does not assign a generated winner or score.
- Sermorelin (GHRHR agonist): Sermorelin is a 29-amino acid analogue of endogenous GHRH (1–44), retaining the N-terminal sequence required for GHRHR binding and activation. GHRHR is a Gs-coupled GPCR expressed almost exclusively in pituitary somatotrophs in the pituitary gland, with limited peripheral expression. Gs coupling elevates cAMP, activating PKA which phosphorylates CREB (promoting GH gene transcription) and triggers Pit-1/POU1F1 transcription factor activity driving GH synthesis, and activates voltage-gated Ca²⁺ channels leading to GH granule exocytosis. Sermorelin’s near-identical mechanism to endogenous GHRH produces the most physiologically authentic GH pulsatility restoration — GHRHR desensitises with continuous exposure but retains pulsatile responsiveness to intermittent dosing.
- Ipamorelin (GHS-R1a agonist): Ipamorelin is a synthetic pentapeptide with selectivity for GHS-R1a — the ghrelin receptor — without significant activity at other receptor systems (unlike GHRP-6, which also activates cortisol/prolactin release through non-GHS-R1a pathways). GHS-R1a is a Gq/G11-coupled GPCR expressed in pituitary somatotrophs, hypothalamic ARC/VMN neurons, and multiple peripheral tissues (heart, kidney, adipose, immune cells). Gq coupling activates PLC-β, generating IP₃ (releasing somatotroph Ca²⁺ from ER) and DAG (activating PKC), triggering GH exocytosis through a Ca²⁺-dependent mechanism complementary but distinct from GHRHR/cAMP/PKA signalling. GHS-R1a also activates a constitutively active form that contributes to basal GH tone independently of ligand binding — a unique pharmacological property relevant to chronic exposure research.