Characteristics of growth hormone response to the administration of growth hormone-releasing hormone (GRF) in the lamb.
Barenton. B B; Duclos. M M; Diaz. J J; Deletang. F F; Dulor. J P JP; Blanchard. M M; Charrier. J J
Key Findings
- GRF‑1‑29 triggers a rapid, dose‑dependent increase in GH within 1‑4 minutes, lasting up to an hour.
- Both newborn (suckling) and older (weaned) lambs respond strongly, even when they already have natural GH spikes.
- Repeated twice‑daily dosing for 21 days boosts the acute GH response, showing no desensitization of the pituitary.
Practical Outcomes
- For biohackers, this suggests that GRF‑1‑29 can reliably raise GH without losing effectiveness over weeks, and that higher doses give bigger spikes. While the study is in lambs, the dose‑response pattern and lack of tachyphylaxis may guide human dosing trials, indicating that a low‑microgram per kilogram range could be a starting point for sub‑cutaneous protocols.
Summary
In baby and teen lambs, a single shot of growth hormone‑releasing hormone (GRF‑1‑29) quickly spikes growth hormone levels, and doing this every day for three weeks makes the response even stronger. The hormone works the same whether you use the short (1‑29) or longer (1‑44) version, and the pituitary doesn’t get used up or stop responding.
Abstract
Human growth hormone releasing hormone (GRF 1-44 or GRF 1-29) was administered to lambs at two different physiological stages (suckling: 5-6 week-old and weaned: 14-15 week-old) when growth hormone (GH) secretory patterns were different: suckling lambs exhibited flat basal GH profiles (5-10 ng/ml) while the weaned lambs had frequent spontaneous episodes of GH release (15-65 ng/ml). The iv injection of GRF evoked an immediate release of GH. In each case, plasma GH levels reached a maximum 1-4 min after the injection. The secretory spike was multiphasic and lasted 30-60 min. Administration of GRF (0.1 microgram/kg) in weaned lambs induced GH pulses with an amplitude comparable to that of endogenous peaks. The induction of a GH peak occurred even when a spontaneous peak immediately preceded the GRF injection. Also, spontaneous peaks were observed during the hour following a GRF-induced GH peak. In suckling lambs, GRF injected intravenously as a single bolus in a range of 0.01 to 0.5 microgram/kg (2 to 100 pmoles/kg) stimulated GH release in a dose-dependent manner. Chronic administration of GRF (0.75 nmole GRF 1-44 or GRF 1-29 per kg twice daily for 21 days) in newborn lambs increased significantly (p less than 0.001) the acute response to GRF during the course of the treatment. GH response to GRF 1-44 and GRF 1-29 was the same. These data show that lambs are highly responsive to GRF action during both suckling and weaning and suggest that there is no in vivo desensitization of the pituitary gland after acute or chronic GRF administration.
Study Information
pubmed
1987
10.1051/rnd:19870405