Myostatin (MSTN), also known as GDF-8, is a transforming growth factor-beta superfamily member that functions specifically as a negative regulator of skeletal muscle growth 1. MSTN null mice display 2-3 fold increases in skeletal muscle mass through combined hyperplasia and hypertrophy 1, establishing its critical role in muscle development. Mechanistically, MSTN operates through the MSTN/SMAD2/3-p38 signaling pathway to suppress myogenic factors and promote muscle atrophy factors 2. Its inhibition increases myogenic differentiation while suppressing atrophic markers like atrogin-1 and MuRF-1 3. MSTN also regulates systemic energy homeostasis through autocrine and paracrine signaling in brown adipose tissue via KLF4 and FGF21 2. Clinically, elevated MSTN levels are implicated in muscle wasting conditions including sarcopenia, cachexia, muscular dystrophy, and age-related muscle loss 4. Therapeutic strategies targeting MSTN inhibition show promise: GLP-1R agonists ameliorate muscle atrophy by suppressing MSTN expression through PKA and PKB signaling 3, while MOTS-c reduces myostatin levels via CK2-PTEN-mTORC2-AKT-FOXO1 pathways 5. Multiple biologics have entered clinical trials for muscle-wasting diseases 4, though no approved treatments currently exist 6.