PTHLH and Hypercalcemia: Further workup showed normal PTH-related peptide (PTHrP) levels (1.2 pmol/L) and normal 1,25-dihydroxyvitamin D levels, suggesting that humoral hypercalcemia and vitamin D dysregulation were unlikely causes. Electrocardiography revealed a normal sinus rhythm with a shortened corrected QT interval (QTc 340 ms) as per Bazett's formula, consistent with hypercalcemia.