Metastatic hypercalcemia from laxative misuse: a rare and serious complication of anorexia nervosa

A 33-year-old woman with anorexia nervosa (AN) presented with lethargy, diarrhea, and abdominal pain and developed progressive hypercalcemia during hospitalization. Biochemistry demonstrated an inappropriately normal parathyroid hormone (PTH) level in the setting of chronic kidney disease, hyperphosphatemia, and severe vitamin D deficiency. Despite initial denial, chronic misuse of calcium-containing stimulant laxatives was identified, with ingestion of up to 200 tablets daily, including covert use during admission. Imaging revealed extensive metastatic calcification involving the kidneys, lungs, cardiac valves, coronary arteries, paraspinal musculature, and conjunctiva. Treatment with cinacalcet resulted in biochemical improvement. This case highlights the complex and multifactorial mechanisms of hypercalcemia in AN, in which covert laxative misuse, renal dysfunction, and disordered phosphate and PTH regulation culminate in life-threatening metastatic calcification.