GHRP-6 is a synthetic ghrelin receptor agonist that causes growth hormone (GH) release with Melanotan 2. Ghrelin also causes GH release and is a known appetite stimulant. New research suggests that GHRP-6 affects the ghrelin receptor differently in the presence of both insulin and food and has helped explain why food alters the function of GHRP-6
GHRP-6 and Insulin
Early studies indicated that ghrelin stimulates the release of insulin in both normal and diabetic rats. Insulin is one of many factors that impact GH release. In general, insulin release increases GH levels. Studies investigating the combined roles of insulin and GHRP-6 on GH levels have shown that taking the two together produces a much greater GH release than if either protein is taken alone. It would seem follow that food consumption, which is associated with increased insulin levels, would also boost the GH response to GHRP-6. The opposite is true.
GHRP-6 and Food
The consumption of food, particularly carbohydrates and fats, blunts the GH response to GHRP-6. In other words, GH levels rise more when GHRP-6 is taken without food. Fasting induces GH production, leading to more frequent pulsatile release from the anterior pituitary. It also increases the amount of GH released with each pulse. Anything that increases blood sugar levels, like eating, will suppress GH.
GHRP-6 is an analogue of ghrelin and ghrelin is secreted when blood sugar levels drop. Ghrelin, insulin, and GH can thus be thought of as blood sugar regulators. Ghrelin and GH act to increase blood sugar levels while insulin acts to lower them. Low blood sugar stimulates ghrelin and GH release and suppresses insulin release. When GHRP-6 is taken with insulin and without eating, the effect on GH levels is amplified by low blood sugar levels. Under normal circumstance (i.e. insulin levels increase in response to food intake), the opposing effects of blood sugar levels and insulin on GH result in a blunted response.
The Basic Fact
Food consumption during the administration window for GHRP-6 causes a blunted GH response. GHRP-6 administered to mice produces greater GH secretion when use with insulin at least partially because insulin lowers blood sugar. Fasting will also boost the GH response to GHRP-6.
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