PTH and hyperparathyroidism: Her laboratory tests revealed severe hypokalemia (serum potassium 1.6 mmol/L; normal range 3.5–5.1), metabolic alkalosis (serum bicarbonate 36 mmol/L; normal range 18–24), severe hypomagnesemia (serum Mg 0.9 mg/dL; normal range 1.6–2.6), hypocalcemia (total calcium 7.1 mg/dL; normal range 8.6–10.2) with a response consistent with hyperparathyroidism (intact parathyroid hormone (PTH) 98.9 pg/ml; normal range 15–68.3).