Primary hyperparathyroidism is a very rare complication following radioactive iodine therapy. There is typically a latency period of more than a decade following radiation exposure and, therefore, it is observed almost exclusively in adults. Consequently, pediatricians are not aware of the association. We present a case of primary hyperparathyroidism due to a solitary parathyroid adenoma occurring in an adolescent male two years following radioactive iodine treatment for papillary thyroid carcinoma. Periodic screening of serum calcium following ablative doses of radioactive iodine for thyroid cancer may be justified even in adolescents. 1. Introduction Primary hyperparathyroidism (P-HPT) is uncommon in children and adolescents with an incidence of 2–5 in 100,000 [1]. Excess parathyroid hormone (PTH) secretion leads to hypercalcemia, hypophosphatemia, nephrocalcinosis, nephrolithiasis, and decreased bone density. Parathyroid adenoma is the most common cause of P-HPT in young patients, representing 65–90% of pediatric cases [1–4]. Multiglandular hyperplasia occurs in 16–27% of pediatric P-HPT, half of which can be attributable to multiple endocrine neoplasia (MEN)-I or MEN-II syndromes or familial non-MEN HPT [1, 2]. Due to its rarity in children, most of the literature on P-HPT in pediatric patients has been limited to case reports and small series [1–4]. Radioactive iodine treatment (RAI) is an accepted treatment for hyperthyroidism associated with Graves’ disease and metastatic papillary thyroid carcinoma (PTC) following surgical resection in adults and children [5, 6]. Cola？o et al. analyzed 47 patients who developed P-HPT following treatment with RAI for benign and malignant disease [7]. A female predominance was observed (89.4% women), with P-HPT occurring at a mean age of 59.4 ± 13.5 years. The average latency period to the development of P-HPT after RAI was 13.5 ± 9.1 years. In this review, two patients with Graves’ disease were less than 18 years old (5 and 11 years) at the time of RAI, and time to development of P-HPT was 31 and 22 years, respectively [8]. Surgical pathology in these individuals revealed 4-gland hyperplasia in one and an adenoma in the other. We report a case of a 17-year-old male who presented with hypercalcemia 2 years following RAI treatment for PTC. To our knowledge, this is the first patient reported with this presumed complication of RAI exposure presenting in the pediatric age range. 2. Case Presentation A 17-year-old male presented to the pediatric emergency room with severe headaches. Past medical history was
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