COMMON INITIAL DOSING REGIMENS

• Typically, 10–25 mg taken orally once daily, often at bedtime to align with natural GH secretion peaks and minimize potential side effects like lethargy.

MECHANISM OF ACTION

• Ibutamoren is a selective agonist of the ghrelin receptor (growth hormone secretagogue receptor, GHSR). By stimulating this receptor, it mimics the effects of ghrelin, increasing endogenous secretion of GH from the pituitary gland. This leads to elevated circulating IGF-1 levels, which mediate many of GH’s anabolic effects, including protein synthesis, muscle growth, and fat metabolism. Unlike direct GH administration, ibutamoren preserves the natural feedback mechanisms and maintains normal pulsatile GH release.

COMMON SIDE EFFECTS

• Metabolic: Increased appetite is a common side effect due to ghrelin receptor activation. Weight gain may occur, particularly due to fluid retention or fat accumulation in predisposed individuals.

• Endocrine: Potential alterations in glucose metabolism, including transient insulin resistance, hyperglycemia, or exacerbation of pre-existing diabetes.

• Neurological: Rare reports of headaches, dizziness, and fatigue.

• Other: Edema and joint pain, likely due to increased IGF-1 levels. Rare cases of tingling or numbness in extremities.

CONTRAINDICATIONS

• Absolute: Hypersensitivity to ibutamoren or its excipients.

• Relative: Caution is advised in individuals with active malignancies, as IGF-1 may promote tumor growth. Individuals with pre-existing metabolic disorders, such as diabetes or severe insulin resistance, should use ibutamoren under medical supervision. Limited safety data exists for use during pregnancy or lactation.

ADDITIONAL NOTES ON EFFICACY

• Ibutamoren is a unique alternative to GH injections, offering the convenience of oral administration and a lower risk of desensitization of GH receptors. However, its effects on GH secretion are less targeted than peptide secretagogues like CJC-1295 or sermorelin.

COMPARISON WITH OTHER HGH SUPPORT MEDICATIONS

• Compared to CJC-1295 and Ipamorelin: Ibutamoren is orally administered, offering convenience compared to injectable peptides. However, CJC-1295 and ipamorelin provide a more targeted stimulation of GH release with fewer effects on appetite and metabolic pathways. Ibutamoren’s action is broader due to its ghrelin receptor activation.

• Compared to Sermorelin and Tesamorelin: Sermorelin and tesamorelin are more precise in stimulating GH secretion without significantly affecting appetite or glucose metabolism. Ibutamoren’s effects are more generalized, which may be advantageous for certain applications, such as addressing appetite loss or generalized GH deficiency.

REFERENCES

• FDA Safety Data Sheet not available

• Copinschi G. Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man. Neuroendocrinology. 1997 [PubMed Link]

• Sigalos JT, Pastuszak AW. The Safety and Efficacy of Growth Hormone Secretagogues. Sex Med Rev. 2018 [PubMed link]

• Liu H, Sun D, Myasnikov A, et al. Structural basis of human ghrelin receptor signaling by ghrelin and the synthetic agonist ibutamoren. Nat Commun. 2021 [PubMed link]

• Murphy MG, Plunkett LM, Gertz BJ, et al. MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. J Clin Endocrinol Metab. 1998 [PubMed link]

• Sinha DK, Balasubramanian A, Tatem AJ, et al. Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Transl Androl Urol. 2020 [PubMed Link]