Endocrine Abstracts

Introduction: Intra thyroidal parathyroid adenoma is an uncommon presentation of primary hyperparathyroidism (PHPT). Herein we report such a patient who had recurrent hypercalcemia after a classical parathyroid exploration.

Case presentation: 45 year old female, home-maker had a long standing history of weakness, back and lower limb pain, loss of appetite. Preliminary evaluation at secondary care level revealed hypercalcemia (18.3 mg/dl) with high intact parathyroid hormone (iPTH, 1244.0 pg/ml). 99mTc SestaMiBi scan revealed left inferior parathyroid adenoma for which she underwent left inferior parathyroidectomy elsewhere. Post operatively her symptoms of hypercalcemia returned within few weeks and further evaluation revealed high iPTH(251.10 pg/ml) with hypercalcemia (10.4 mg/dl). Repeat MiBi scan revealed suspected parathyroid adenoma in relation to lower pole of left lobe of thyroid suggesting failed surgery. HR-USG neck revealed no parathyroid adenoma in usual locations and a left lobe thyroid nodule which roughly corresponded to the isotopic activity. USG guided FNAC was non contributory. Patient was subjected to re-exploration by a parathyroid surgeon. Left hemi-thyroidectomy was done and the intrathyroidal mass was removed. Pre-operative iPTH of 1988 pg/ml came down to 55.9 pg/ml within 4 hours of surgery. Intra-opeartive imprint smear showed small clusters of tumor cells with normal to moderate cytoplasm and round to oval nuclei. HPE showed a well circumscribed tumour within left lobe of thyroid with an incomplete fibrous capsule surrounded by thyroid tissue without any capsular or vascular invasion. There were polygonal cells with moderate amount of clear cytoplasm and round to oval hyperchromic nuclei and mild anisocytosis. Post-operative hypocalcemia (6.9 mg/dl) was managed with intravenous calcium and magnesium and oral calcitriol. Patient continues to be on oral calcium plus calcitriol supplement at the 7th post operative week of the second surgery.

Discussion: In a large series of >10,000 parathyroid exploration for PHPT, 1.2% were partially intrathyroidal while only 0.7% were truly intrathyroidal¹. Most reported cases were typically diagnosed due to persistent disease post-exploration².

Conclusion: Intrathyroidal parathyroid adenoma is a rare cause of PHPT and should be considered as a potential cause for a unsuccessful parathyroid exploration.

References: 1. Goodman A, Politz D, Lopez J, Norman J. Intrathyroid Parathyroid Adenoma: Incidence and Location—The Case against Thyroid Lobectomy. Otolaryngology–Head and Neck Surgery. 2011;144(6):867-871.

2. Scheidt M, Hubbs D, Kabaker A, et al. Completely Intrathyroidal Parathyroid Adenoma in a Patient with a Previously Failed Cervical Exploration. World J Endoc Surg 2020;12(3):136–139.