Arginine Pyroglutamate/Lysine is an amino acid combination that has recently gained significant attention in the US bodybuilding market. Interest in this compound surged following a notable Italian study conducted in 1981 by Dr. A. Isidori and his colleagues at University Clinic V in Rome. They demonstrated that arginine pyroglutamate (L-arginine-2-pyrrolidone-5-carboxylate) possesses remarkable growth hormone-releasing properties when administered alongside L-lysine hydrochloride.
In their study, a dosage of 1.2 grams of arginine pyroglutamate combined with 1.2 grams of L-lysine hydrochloride resulted in a staggering 700% increase in serum growth hormone levels after just 90 minutes. This increase was not only significant but also sustained; even after eight hours, the blood plasma levels of growth hormone remained 300% above normal. What made these results particularly surprising was that they were achieved through oral administration, contrary to previous studies that indicated such effects could only be observed with injections or infusions.
The simultaneous rise in serum insulin levels by 300% within 30 minutes further supported the notion that the increased growth hormone release was biologically active. Insulin is essential for the liver to produce somatomedins and insulin-like growth factors (IGF-1 and IGF-2), which are crucial for muscle development. The findings suggested that arginine pyroglutamate/lysine could be an effective combination for muscle gain and fat loss.
Interestingly, the study found no significant difference in growth hormone release between male and female participants, which was unexpected given the known estrogen dependency of growth hormone secretion. Moreover, the researchers noted that the growth hormone-releasing effect only occurred when arginine pyroglutamate and L-lysine hydrochloride were taken in a balanced ratio of 1:1; deviations from this ratio or taking the amino acids separately yielded no similar positive results.
Despite these promising findings, skepticism remains regarding the practical benefits of arginine pyroglutamate/lysine supplementation for bodybuilders. Critics argue that Isidori’s study may have methodological flaws, as other research does not corroborate such dramatic increases in growth hormone levels from this combination. Dr. Michael Colgan has pointed out that these results are inconsistent with existing literature, leading to exaggerated claims about arginine/lysine supplements.
In practical terms, many professional bodybuilders continue to rely on expensive synthetic growth hormone injections rather than turning to arginine pyroglutamate/lysine supplements. The physiological output of a healthy human pituitary gland, which releases about 1 international unit (i.u.) of growth hormone daily, raises questions about whether a 700% increase would realistically translate to effective muscle-building results.
Athletes who have tried this amino acid combination report mixed outcomes, with many expressing disappointment over a lack of significant muscle gain or fat loss after using the recommended dosage of 1.2 grams per day over several weeks. Attempts to increase dosage did not yield better results either, leading to the conclusion that arginine pyroglutamate/lysine may not effectively stimulate growth hormone release as claimed.
For those interested in trying arginine pyroglutamate/lysine, it is advised to take it on an empty stomach—preferably first thing in the morning and before bed—and to allow four weeks to assess its impact on muscle gain and fat loss. Although no adverse side effects have been reported at recommended dosages, users should remain realistic about their expectations.
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