In clinical practice,serum electrolytes of patients with hyperthyroidism are often ignored.The prevalence of hypercalcemia in patients with thyrotoxicosis was 17％ to 50％ in literatures,1,2 and asymptomatic serum calcium elevation has been documented in up to 20％.1 We described a case of hypercalcemia related to thyrotoxicosis,which had been neglected by the doctors at the first visit.