an understandable write up - china mans is ghrp2 but little difference
The secretion of growth hormone (GH) from the pituitary gland is regulated by the central nervous system. At the hypothalamic level, two peptides, growth hormone releasing hormone (GHRH) and somatostatin modulate the secretion of GH. GHRH stimulates GH secretion while somatostatin exhibits an inhibitory influence.
Other peptides of different size and structure are able to influence GH secretion in man and several other animal species. Amongst these, a synthetic hexapeptide (GHRP-6), derived from an enkephalin analogue, specifically stimulates GH release both after parenteral and oral administration. The oral activity of GHRP-6 has opened up new perspectives in the treatment of several conditions associated to hypothalamic growth hormone deficiency. It has also prompted the development of new synthetic peptides, possessing greater potency, a longer duration of action and an increased oral bioavailability.
Hexarelin (INN:Examorelin, MF 6003, EP 23905) is a new synthetic peptide formed by 6 aminoacids. Its chemical structure is His-DTrp(2-Me)-Ala-Trp-DPhe-Lys-NH2. Compared to GHRP-6, hexarelin is more resistant to proteolytic degradation.
An extensive package of toxicological studies has been performed. No organ specific toxicity was observed. No toxic effects were recorded on the cardiovascular system, renal function and CNS. Pharmacokinetic studies are available in rats and dogs. The drug is absorbed by the subcutaneous and oral routes. The half-life of hexarelin is 2 hours in dogs after bolus iv administration.
Hexarelin stimulates GH secretion following intravenous, subcutaneous, intranasal and oral administration. In man, a bolus intravenous dose of 1 mg/kg induces peak plasma GH concentrations of around 70 ng/mL within 15 minutes. The mechanism of action of hexarelin has still not been fully elucidated. The peptide seems to act on pituitary binding-sites and to modulate intracellular messenger pathways different from those associated with GHRH. Its low toxicity, marked and specific stimulation of GH secretion along with its rapid absorption after oral administration, strongly indicate that it could be employed as a diagnostic and therapeutic tool in GH secretory disorders.
High-affinity binding sites for hexarelin have been identified in human cardiac and vascular tissues. Various animal models have evidenced a strong protective effect of hexarelin in post-ischemic ventricular dysfunction. Hexarelin improves cardiac function in rats with experimentally induced congestive heart failure. These cardiovascular effects have also been observed in hypophysectomized animals and occur at doses far lower than those required to elicit GH secretion.
Hexarelin has been administered to about 1,000 subjects. Phase 1 studies have shown that the drug is well tolerated after i.v. administration of doses up to 2 mg/kg. Chronic intranasal administration of hexarelin has been shown to accelerate growth in short children. Endocrine effects have been demonstrated after chronic oral administration in elderly subjects.
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