MRAP and Hyponatremia: Fewer children with NNT (two of seven, 28%), MRAP (two of nine, 22%), and MC2R (2 of 25, 8%) mutations required mineralocorticoid replacement, although four additional children with MC2R defects had transient hyponatremia (sodium 117–133 mmol/L) that resolved without fludrocortisone treatment (Supplemental Table 1).