A Challenging Diagnosis of Primary Hyperparathyroidism in an Adolescent Female

Background: Hypercalcemia secondary to primary hyperparathyroidism (PHPT) is less common in children than adults. Single parathyroid adenoma is commonly the cause of primary hyperparathyroidism in children. Clinical Case: We present a 15-year-old female with one-week history of abdominal pain despite taking over the counter antacids. Her initial work up by her primary care provider revealed serum calcium of 11.8 mg/dL (9.0–11.5) and creatinine of 0.8 mg/dL (0.4–1.2). A week later, she presented to the emergency department with same complaint. In ED, she was found to have hypercalcemia (12.8 mg/dl) with elevated parathyroid hormone (PTH) at 78.5 pg/mL (15–65). Her random urine calcium creatinine ratio was high at 2.1. Her 25OHD was 25 ng/mL (30–100). She had negative urine pregnancy test but had trace ketones, leukocyte esterase, blood and bacteria. CBC and CMP were otherwise unremarkable. She continued to complain abdominal pain with nausea, decrease appetite, fatigue, and general muscle weakness. There was no known family history of calcium or metabolic bone disorders. Her vital signs and physical exam were normal. Subsequent labs showed mild improvement of calcium between (11–12.3 mg/dL), PTH between 54.5 and 77 pg/mL, normal thyroid function. Ionized calcium was mildly elevated 6.0 mg/dL (4.5–5.3) but her repeat 25OHD was low at18 ng/mL. Serum phosphorus levels were relatively normal with lowest level of 2.5 mg/dL (2.7–4.5). Gliadin Deamidated IgA was detectable 15 U/mL (< 15.0 U/). Ultrasound of abdomen was significant for nonspecific mild hepatomegaly; kidneys were normal in size and appearance. Ultrasound of thyroid was significant for probably intrathyroid parathyroid, measuring 6 x 8 x 8 mm. Tc-Sestamibi scan did not confirm a parathyroid adenoma. Genetic testing for MEN-1 was negative. FHH- related genes (i.e. CASR) was positive for p.R990G variant resulting in a mild gain of function of the calcium-sensing receptor. Although previous Tc-Sestamibi scan was unremarkable, an over read of it raised a concern for questionable uptake in the left superior lobe. SPEC-CT demonstrated possible abnormal parathyroid tissue in the upper pole of the left thyroid. FNA of the left thyroid nodule confirmed likely intrathyroidal parathyroid adenoma. Subsequent follow up and treatment, including parathyroidectomy, was done by another institution. She underwent a left parathyroidectomy with normalization of serum calcium and PTH levels post operatively (10.1 mg/dl and 8 pg/mL, respectively) and has complete resolution of her previous abdominal and gastrointestinal symptoms. Conclusion: PHPT is uncommon in children and adolescents and is typically associated with a single parathyroid adenoma. High index of suspicion is key for early diagnosis of PHPT despite a negative Tc-Sestamibi initially.