Part of “CHAPTER 59 – NONPARATHYROID HYPERCALCEMIA“

Hypercalcemia, through its effect on cellular sodium-potassium adenosine triphosphatase, leads to hyperpolarization of cell membranes. This hyperpolarization or refractoriness of cell membranes is particularly apparent in nervous and muscle tissue. Neurologic manifestations of hypercalcemia include the spectrum of metabolic central nervous system dysfunction, which involves apathy, drowsiness, and depression, progressing to obtundation and coma (see Chap. 200). Skeletal muscle and neurologic dysfunction may present as weakness (see Chap. 210). Smooth-muscle hyperpolarization may be manifest as bowel hypomotility and constipation. The most reproducible cardiac conduction abnormality is a shortening of the QT_c interval.