Pre- versus postmenopausal age, estradiol, and peptide-secretagogue type determine pulsatile growth hormone secretion in healthy women: studies using submaximal agonist drive and an estrogen clamp.
Hudson. Susan B SB; Schroeder. Darrell R DR; Bailey. Joy N JN; Mielke. Kristi L KL; Erickson. Dana D; Miles. John M JM; Bowers. Cyril Y CY; Veldhuis. Johannes D JD
Key Findings
- Younger (pre‑menopausal) women produce more pulsatile GH than older (post‑menopausal) women, even when body fat and baseline GH are accounted for.
- Adding estrogen (estradiol) boosts both overall GH levels and the size of GH pulses, especially in younger women.
- GHRP‑2 stimulates GH pulses more effectively than GHRH when given at a half‑maximal dose.
Practical Outcomes
- For biohackers interested in GH‑boosting protocols, the data suggest that GHRP‑2 is a more potent secretagogue than GHRH, and that estrogen status can further amplify its effect. Women considering GH‑enhancement may benefit from ensuring adequate estradiol levels (e.g., through hormone replacement) when using GHRP‑2. The findings are less directly applicable to men, but highlight the importance of hormonal milieu in peptide efficacy.
Summary
The study shows that in healthy women, the amount of growth hormone released in pulses depends on three things: how old the woman is, whether she has enough estrogen, and which peptide is used. Younger women, those given estrogen, and those given the peptide GHRP‑2 all had stronger, more frequent GH spikes than older women, those without estrogen, or those given GHRH.
Abstract
GH-releasing peptide (GHRP), GHRH, and somatostatin are physiological regulators of pulsatile GH secretion. Age, independently of abdominal visceral fat (AVF) and basal (nonpulsatile) GH secretion, damps pulsatile GH secretion driven by physiological (rather than pharmacological) amounts of GHRP and GHRH in an experimentally controlled estradiol (E(2)) milieu. A prospectively randomized, double-blind parallel-cohort study was conducted at an academic medical center. Community-dwelling healthy premenopausal (PRE, age 24 +/- 0.8 yr, n = 20) and postmenopausal (POST, age 63 +/- 1.8 yr, n = 22) women participated in the study. Gonadal-axis down-regulation with leuprolide was followed by randomized addback of placebo or transdermal E(2) and separate-day iv bolus injections of a half-maximally stimulatory dose of GHRP-2 or GHRH (each 0.33 mug/kg). Three-way analysis of covariance included main factors age, E(2) status, and secretagogue type and covariates AVF and basal GH secretion. Submaximally stimulated pulsatile GH secretion was positively determined by PRE vs. POST age (P < 0.001), E(2) repletion vs. depletion (P = 0.001) and GHRP-2 vs. GHRH stimulation (P < 0.001), after adjustment for AVF and basal secretion. E(2) vs. placebo elevated fasting mean GH concentrations in both PRE and POST women (P = 0.006) but increased basal (nonpulsatile) GH secretion in PRE only (P = 0.002). PRE vs. POST age prolonged GHRH-driven GH secretory bursts by 36% (P = 0.006). PRE vs. POST age, E(2) availability, and physiological peptide drive are triple determinants of pulsatile GH secretion independently of abdominal visceral fat and nonpulsatile GH secretion in healthy women.
Study Information
pubmed
2009
2009-10-26T00:00:00.000Z
10.1210/jc.2009-1769
18
37