Complex regulation of GH autofeedback under dual-peptide drive: studies under a pharmacological GH and sex steroid clamp.
Veldhuis. Johannes D JD; Erickson. Dana D; Miles. John M JM; Bowers. Cyril Y CY
Key Findings
- Combined GHRH and GHRP-2 infusion produces larger GH peaks than either peptide alone, independent of sex hormones.
- Supplementing with estrogen (in women) or testosterone (in men) raises the lowest (nadir) GH levels and further boosts peaks when only saline is infused.
- Women showed higher GH peak responses to the dual‑peptide combo than men.
Practical Outcomes
- For biohackers, pairing GHRP-2 with a GHRH analog (like sermorelin or ipamorelin) is likely to give stronger GH spikes than using GHRP-2 alone. Adding sex‑hormone therapy could amplify the effect, but the study used IV dosing in older adults, so real‑world sub‑Q dosing and younger users may see different results. Caution and personal experimentation are advised.
Summary
The study shows that giving both a GHRH analog and GHRP-2 together makes the body release a bigger burst of growth hormone than giving either one alone, and that adding estrogen or testosterone also lifts the baseline and peak hormone levels. Women had slightly higher peaks than men. These effects were seen in older adults using IV infusions, which is different from the typical sub‑Q injections used by most hobbyists.
Abstract
To test the postulate that sex difference, sex steroids, and peptidyl secretagogues control GH autofeedback, 11 healthy postmenopausal women and 14 older men were each given 1) a single iv pulse of GH to enforce negative feedback and 2) continuous iv infusion of saline vs. combined GHRH/GHRP-2 to drive feedback escape during pharmacological estradiol (E(2); women) or testosterone (T; men) supplementation vs. placebo in a double-blind, prospectively randomized crossover design. By three-way ANCOVA, sex difference, sex hormone treatment, peptide stimulation, and placebo/saline responses (covariate) controlled total (integrated) GH recovery during feedback (each P < 0.001). Both sex steroid milieu (P = 0.019) and dual-peptide stimulation (P < 0.001) determined nadir (maximally feedback-suppressed) GH concentrations. E(2)/T exposure elevated nadir GH concentrations during saline infusion (P = 0.003), whereas dual-peptide infusion did so independently of T/E(2) and sex difference (P = 0.001). All three of sex difference (P = 0.001), sex steroid treatment (P = 0.005), and double-peptide stimulation (P < 0.001) augmented recovery of peak (maximally feedback-escaped) GH concentrations. Peak GH responses to dual-peptidyl agonists were greater in women than in men (P = 0.016). E(2)/T augmented peak GH recovery during saline infusion (P < 0.001). Approximate entropy analysis corroborated independent effects of sex steroid treatment (P = 0.012) and peptide infusion (P < 0.001) on GH regularity. In summary, sex difference, sex steroid supplementation, and combined peptide drive influence nadir, peak, and entropic measurements of GH release under controlled negative feedback. To the degree that the pharmacological sex steroid, GH, and dual-peptide clamps provide prephysiological regulatory insights, these outcomes suggest major determinants of pulsatile GH secretion in the feedback domain.
Study Information
pubmed
2011
2011-04-05T00:00:00.000Z
10.1152/ajpendo.00054.2011
8
49