Case Presentation
A 65-year-old woman was referred to our hospital because of hypercalcemia. She had undergone total thyroidectomy for thyroid cancer 30 years prior along with left-sided parathyroid auto-transplantation in her neck, without any family history of endocrine diseases. Physical examination showed a surgical scar on the left side of her neck (Fig. 1 ). Her serum calcium, phosphate, and intact parathyroid hormone levels were 11.3 mg/dL, 3.4 mg/dL, and 170 pg/mL, respectively. Tc-99m-MIBI demonstrated increased uptake in the autograft in the left supraclavicular region (Fig. 2 ). Based on these findings, primary hyperparathyroidism due to the autografted parathyroid gland was strongly suspected. Although parathyroid tissue auto-transplantation is useful for preventing hypoparathyroidism during thyroidectomy, hyperparathyroidism may occur due to proliferation of the transplanted parathyroid tissue (1, 2). This case suggests that long-term regular monitoring of serum calcium levels may be necessary after parathyroid auto-transplantation even in patients without multiple endocrine neoplasia.