Endocrine Abstracts

Hypercalcaemia due to primary hyperparathyroidism (PHPTH) is fully curable by parathyroidectomy. Occasionally recurrent hypercalcemia presents as a results of either residual adenoma, recurrent disease or an ectopic parathyroid gland. The most challenging cases are those with ectopic glands which are not identified on usual surgical neck exploration. We present a similar case that went through multiple surgeries for recurrent hypercalcemia. A 79-year-old lady initially was diagnosed as primary hyperparathyroidism (in 2009) with symptomatic hypercalcaemia (2.84–3.0 mmol/l) and raised PTH (8.8–11 pmol/l). Multiple parathyroid imaging modalities (CT scan neck, SESTAMIBI and Ultrasound) failed to identify any adenoma. She underwent first surgical exploration in 2010 and three parathyroid glands were removed (both right glands and left superior gland). One gland was suspected to be adenoma. Histology confirmed hyperplastic parathyroid glands. Postoperative biochemistry didn’t normalise and she continued to have persistent primary hyperparathyroidism (Corrected calcium = 2.79 mmol/l, PTH = 10.3 pmol/l). She had osteoporotic wrist fracture. Further imaging to identify parathyroid adenoma was done (CT scan neck and chest with contrast) in 2012. No adenoma was identified again and the plan was to proceed with another surgical neck exploration in 2012. The residual hyperplastic parathyroid left inferior parathyroid gland could not be located and PHPTH was not resolved postoperatively (Corrected calcium = 2.66 mmol/l, PTH = 8pmol/l, Vitamin D of 20 nmol/l). Due to low vitamin D levels, it was thought to be mild secondary hyperparathyroidism. Low dose Cholecalciferol was advised to prevent further growth of the remaining hyperplastic gland and subsequent end organ damage. Vitamin D repletion failed to correct the Calcium (2.6–2.8 mmol/l) and PTH levels (9–10 pmol/l). In view of symptomatic hypercalcaemia with ongoing end organ damage it was decided to reimage her with newer modalities and explore for ectopic mediastinal parathyroid adenoma. 4D CT scan identified an ectopic parathyroid adenoma in the left trachea-oesophageal groove posterior and inferior to the lower pole of the left lobe of thyroid gland. A 3^rd neck exploration in 2020 successfully excised the ectopic parathyroid tissue which was confirmed to be adenoma on histology. The biochemistry was normalised (Ca 2.24 mmol/l, PTH 2.8 pmol/l) and her symptoms settled. The ectopic parathyroid adenomas (3–4% of all parathyroid adenomas) occur as a result of embryonic migration during foetal development. The actual prevalence of mediastinal parathyroid adenomas is unrecognized but it ranges from 6–30%. Surgical neck exploration can be facilitated by use of modern imaging techniques like 4D CT scan (sensitivity = 96.7%, specificity = 95.7%) to identify ectopic parathyroid glands.