PTH and muscular atrophy: However, several authors have cited some risks factors for muscle weakening, such as carnitine deficiency, malnutrition, myopathy, muscular atrophy, parathyroid hormone (PTH) excess and toxicity, uremic toxins and vitamin D deficiency.28,29 There is also atrophy of both types of fibers, mainly type II fibers.28 These findings may explain the low adherence to engagement in physical activity.