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GH-Peptide Selection Deep Dive — Which One Is Right For You

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GH-Peptide Selection Deep Dive — Which One Is Right For You

Provenance: educational study-synthesis (secondary source); companion to the GH-admin guide

Mechanism + clinical-data review on selecting a GH peptide. “Educational, not medical advice.” Tagged [educational]; research/educational use only. Source: YouTube — MVG006bW_3s (Thorough structured capture; full verbatim not stored.)

The core tension

Raising GH/IGF-1 is not a clear-cut anti-aging win. Benefits (muscle, bone, recovery, sleep, cognition, fat loss — esp. visceral) vs downsides: insulin resistance, cancer progression (each +38 ng/mL IGF-1 ≈ +8–18% risk for most cancers; GH doesn’t cause cancer but feeds existing), and a likely U-shaped IGF-1↔mortality curve (both too-low and too-high raise mortality; animal models: lower GH/IGF-1 → longer life). GH falls ~1%/yr after 30 (somatopause), but direct GH replacement is only recommended for pathologic deficiency, not aging. Goal: augment physiology, don’t override it.

GH axis (physiology)

GHRH (hypothalamus, 44 aa) → pituitary GH → liver IGF-1. Somatostatin = negative feedback (↑ by eating + by IGF-1). Ghrelin (stomach, fasting) hits GHSR-1A → ↑GHRH + inhibits somatostatin + direct pituitary GH → synergy with GHRH. Release is pulsatile (93% in pulses every 2–3 h; 7% basal); the post-sleep-onset nighttime pulse is largest (males 70–85% of daily GH at night; females more daytime/irregular). Aging lowers pulse amplitude, not frequency or basal — a key fact for peptide choice.

Structures, half-lives, potency

  • GHRH 44 aa (t½ 6–10 min). Tesamorelin = 44 aa + trans-hexenoic acid (anti-degradation; t½ 8–38 min; potency ≈ GHRH). Sermorelin = first 29 aa unmodified (t½ 10–20 min; potency ≈ GHRH). CJC-1295 without DAC (= modified GRF 1-29) = those 29 aa + 4 amino-acid changes (stability + ~4× potency vs sermorelin, rat) → t½ ~20–50 min; no studies. CJC-1295 (with DAC) = adds maleimidopropionic acid → albumin binding → t½ 5.8–8.1 days.
  • Naming caution: in the literature “CJC-1295” means with DAC; “without DAC” is a different peptide (modified GRF 1-29).

The DAC problem (non-physiologic)

CJC-1295-with-DAC raises basal/trough GH ~7.5× while leaving pulses unchanged — but aging is lost pulse amplitude, not low basal, so this is “exactly what you don’t want.” Persistently elevated GH means you never drop to the low trough where AMPK/sirtuin cleanup-repair (longevity) pathways switch on, instead living in mTOR/IGF-1 growth pathways → theoretically worse for lifespan and cancer. Short-acting GHRHs instead raise pulse amplitude (up to 2.5×) and return to baseline = physiologic. MK-677 has the same flaw (raises trough ~3.5×).

Clinical data

  • Sermorelin: ~100 adults across small studies; ~+50% IGF-1, body-comp gains; notably improves (not harms) insulin sensitivity.
  • Tesamorelin: FDA-approved (HIV lipodystrophy), 1,000+ patients; +80% IGF-1, −11–18% visceral fat, ↓triglycerides/↑HDL, ↓inflammation. Insulin-resistance nuance: worse early (fasting glucose +9 at 2 wk), neutralised by ~6 mo if visceral fat is lost; those losing <8% visceral fat had +8 fasting glucose / +0.2 A1C at 1 yr; 5% developed diabetes vs 1% placebo. ~50% formed antibodies (60% cross-reactive to endogenous GHRH) but efficacy unaffected; antibodies wane (18% persist at 6 mo).
  • CJC-1295 without DAC: no studies (big caveat) — inferred ≥ tesamorelin-level effect + its insulin-resistance risk.
  • CJC-1295 with DAC: only tiny phase-1 (+50–200% IGF-1, no outcomes); a phase-2 (HIV lipodystrophy, 120 pts) was terminated and never published after a participant death (deemed unrelated cardiac) → extra caution.
  • Cost: sermorelin & CJC-no-DAC cheapest; CJC-DAC slightly more; tesamorelin most expensive.

GHRPs (the add-on class)

Differentiators: half-life, GH potency, appetite stimulation, selectivity (impact on other axes). Ghrelin (28 aa): highest potency+appetite, least selective. GHRP-6 (6 aa): highest appetite, ↑ACTH/cortisol at high dose. GHRP-2 & hexarelin: more potent than GHRP-6; hexarelin uniquely improves cardiac performance (post-CABG). Ipamorelin (5 aa): GH ≈ GHRP-6 but HIGHLY selective — no ACTH/cortisol even at high doses in swine, mild appetite → the standout. MK-677 (ibutamoren, non-peptide, oral): most human data (incl. a 500+ patient Alzheimer’s year-long trial), +70% IGF-1 in older adults — but non-physiologic (trough ↑3.5×), insulin resistance (+5 glucose, +0.2 A1C over 2 yr), one trial stopped for CHF risk, appetite, mild ACTH/cortisol/prolactin.

Why GHRH base + GHRP add-on (synergy)

GHRP monotherapy fails long-term: GHSR rapidly desensitizes + chronic GHRP raises somatostatin → IGF-1 doesn’t rise (16-wk hexarelin study; restored after a 4-wk break). GHRH desensitizes far less and upregulates synthesis of the GHSR receptors → counteracts GHRP downregulation. Combined, human data show a 66% synergistic GH increase (expected sum 2,400 → actual 4,200). Pulsatile ipamorelin synergizes better than continuous MK-677.

Selection summary

  • GHRH base: Sermorelin (gentle/physiologic/starter) → Tesamorelin (potent, most-studied, expensive) → CJC-1295 without DAC (cost-effective, mechanistically superior, unproven). CJC-1295 with DAC = off the table if prioritising health/longevity.
  • GHRP add-on (only if needed): Ipamorelin (the only selective one; used for synergy, not max potency).
  • Decision matrix — lean higher potency if: low IGF-1, high visceral fat, high triglycerides/low HDL, large waist, low muscle. Lean lower/avoid if: high IGF-1, insulin resistance/diabetes, cancer predisposition (active/genetic = full stop), fluid-retention-prone. Age >60–65 and females → start with sermorelin (more adverse-effect risk; titrate up only if needed).

Candidate notes reinforced (no note yet)

MK-677 / ibutamoren (now noted as the most human-studied GHRP — overdue), GHRP-6, GHRP-2, hexarelin; concept candidates: somatostatin, ghrelin, GHSR-1A, somatopause, AMPK/sirtuins vs mTOR.

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