Endocrine Abstracts

Introduction: Hypercalcemia is a common clinical abnormality seen in clinical practice. One of the leading causes of hypercalcemia is Primary hyperthyroidism from a parathyroid adenoma. While the ectopic parathyroid tissue is typically found in the thymus and anterior mediastinum, Intrathyroidal parathyroid adenoma is a challenging cause of primary hyperparathyroidism leading to persistent hypercalcemia even post-surgery.

Case History: We present a case of 75-year-old female who presented with symptomatic, refractory hypercalcemia who initially underwent two parathyroidectomies.

Initial investigations: Adj Ca 2.9 and PTH 23.7. Sestimibi scan and US parathyroid detected no parathyroid adenoma. She had a neck exploration and biospy suggested right superior parathyroid adenoma.

Progress: She presented after her first parathyroidectomy with symptomatic hypercalcemia with an Adjusted Ca 3.05 and PTH 53. Subsequent Ultrasound parathyroid detected no parathyroid lesions however a 1cm thyroid nodule on the posterior aspect of the right thyroid gland was found.A CT CAP was performed to exclude malignancy which was unremarkable She had a re-do bilateral parathyroidectomy and biopsy samples confirmed left superior and inferior parathyroid hyperplasia Repeat Sestamibi scan showed that appearances were suggestive of a right parathyroid adenoma probably intrathyroidal. She continued to have frequent hospital admissions with severe symptomatic hypercalcemia and a PET CT was requested to ascertain the cause of her hypercalcemia. Her PET CT showed large 2cm parathyroid adenoma in the Right thyroid gland. She had a right thyroid lobectomy which showed a large 2cm intrathyroidal parathyroid and her PTH dropped from 112 to 1.7. Histology confirmed atypical intrathyroidal parathyroid. She remained well and normocalcemic after that.

Discussion: Incidence of IPAs range from 0.7% to 6%. IPAs can be challenging to manage due to complexity of the location. They are often difficult to localize preoperatively and intraoperatively. Studies have shown that MIBI-based techniques are useful in detecting IPA. They have a sensitivity of 60%–83% in detecting IPAs.