Ghrelin
Ghrelin
Ghrelin is a 28-amino acid acylated peptide hormone produced primarily by ghrelinergic cells in the gastrointestinal tract, often called the 'hunger hormone' due to its potent orexigenic effects. It is primarily used in research contexts to stimulate appetite, promote growth hormone secretion, and study metabolic and neuroendocrine regulation. Clinically, it has been investigated for cachexia, anorexia nervosa, gastroparesis, and post-surgical recovery where appetite stimulation and GI motility support are desired.
Mechanism of Action
Ghrelin binds to the growth hormone secretagogue receptor 1a (GHSR-1a), a G-protein coupled receptor expressed in the hypothalamus, pituitary, and peripheral tissues, activating Gq/11 signaling pathways that stimulate appetite via neuropeptide Y and AgRP neurons in the arcuate nucleus. It also potently stimulates growth hormone release from the anterior pituitary, independent of GHRH, through calcium-mediated signaling cascades. Additionally, ghrelin modulates insulin secretion, gastric motility via vagal afferents, energy homeostasis, and exerts cardioprotective and anti-inflammatory effects through peripheral GHSR activation.
Evidence by Health Goal(18 goals)
Dosing Protocols
Administered subcutaneously or intravenously in the morning and/or pre-meal on an empty stomach to maximize orexigenic and GH-releasing effects
Cycle: Typically used for defined study periods of 2-8 weeks; long-term cycling protocols are not well established
Clinical research protocols have used intravenous infusions (1-5 mcg/kg bolus) or subcutaneous injections. Subcutaneous administration has lower bioavailability than IV but is more practical. Acylated (active) ghrelin degrades rapidly; half-life is approximately 30 minutes, necessitating careful timing. Research-grade only; not approved for human therapeutic use outside clinical trials.
Safety & Side Effects
Ghrelin has demonstrated a generally acceptable short-term safety profile in clinical trials at physiological replacement doses, but it is not approved by the FDA or EMA for any therapeutic indication and remains investigational. Long-term safety data are limited, and its effects on tumor growth promotion via GH axis stimulation and potential metabolic dysregulation warrant caution, particularly in individuals with obesity, diabetes, or hormone-sensitive conditions.
Possible Side Effects
- !Transient hunger and increased food intake within 30-60 minutes of administration
- !Flushing and warmth sensations at the injection site or systemically
- !Mild transient hypoglycemia or blood glucose fluctuations due to reduced insulin secretion
- !Nausea or gastrointestinal discomfort, particularly at higher doses
- !Transient elevations in cortisol and prolactin secondary to GHSR activation
- !Injection site reactions including erythema, swelling, or bruising
- !Tachycardia or mild palpitations reported in some clinical study participants
Interactions
- -May blunt insulin secretion and elevate blood glucose - use with caution alongside antidiabetic medications including insulin and metformin
- -Additive GH-stimulating effects when combined with GHRH analogs (e.g., sermorelin, tesamorelin) or other GH secretagogues such as MK-677, increasing risk of GH-excess side effects
- -May antagonize the appetite-suppressing effects of GLP-1 receptor agonists (e.g., semaglutide, liraglutide) through opposing hypothalamic pathways
- -Potential interaction with corticosteroids, which can upregulate GHSR expression and amplify ghrelin's orexigenic and cortisol-stimulating responses
- -May enhance gastric motility when combined with prokinetic agents (e.g., metoclopramide), potentially altering drug absorption kinetics
Cost & Where to Buy
Research-grade acylated ghrelin is available from peptide vendors at approximately $40-$200 per vial (1-5 mg); monthly cost depends heavily on body weight-based dosing, frequency, and vendor purity standards. Pharmaceutical-grade ghrelin for clinical use is substantially more expensive and only available through institutional channels or clinical trials.
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