Several factors have been demonstrated to be responsible for muscle wasting during HF, including reduced local insulin-like growth factor I (IGF-I) expression [3], increased muscular tumor necrosis factor alpha (TNF-α) [4], increased myostatin expression [5], and overexpression of the E3-ligases Muscle RING Finger 1 (MuRF-1) and atrogin-1/Muscle Atrophy F-Box (MAFbx), which activate the ubiquitin–proteasome system [6]. Here, MSTN is linked to hydrops fetalis.