Rationale: Hyperthyroidism is one of the major clinical causes of hypercalcaemia, however, hyperthyroidism-related hypercalcemic crisis is rare, only 1 case have been reported. The potential mechanisms are still not too clear. It may be related that thyroid hormone stimulate bone turnover, elevate serum calcium, increase urinary and fecal calcium excretion.
Patient concerns: A 58-year-old female patient was found to have Graves' disease, a marked elevated serum calcium level (adjusted serum calcium: 3.74 mmol/L), and reduced parathyroid hormone level.
Diagnoses: She was diagnosed as hyperthyroidism-associated hypercalcemic crisis.
Interventions: Treatment with methimazole to correct the hyperthyroidism and treatment of the patient's hypercalcaemia was achieved by physiological saline, salmon calcitonin and furosemide.
Outcomes: After treatment for hypercalcaemia and hyperthyroidism, her symptoms and serum calcium levels quickly returned to normal.
Lessons: hyperthyroid-associated hypercalcaemia crisis is rare, however, the diagnosis should pay attention to screening for other diseases caused by hypercalcemia. Timely treatment of hypercalcaemia is a critical step for rapidly control of symptoms, and treatment of hyperthyroidism is beneficial to relief the symptoms and maintain the blood calcium level.