(11.12) Asymptomatic Severe Hypercalcemia: a Case of a Large Parathyroid Adenoma

Parathyroid adenomas are benign tumors and account for 80-90% of cases of primary hyperparathyroidism (PHPT). The majority of people with PHPT are asymptomatic and have a parathyroid hormone (PTH) level 1.5-2x the upper limit of normal and a serum calcium level in the upper normal to mildly elevated range. We describe an atypical case of a solitary parathyroid adenoma that presented with significantly elevated PTH and severe hypercalcemia.


Case(s) Description : A 43-year-old woman was incidentally found to have uncorrected serum calcium of 14.6 mg/dL (8.6 –10.0), albumin 3.7 g/dL (3.5-5.2), ionized calcium 7.4 mg/dL (4.4-5.2), and PTH 423 pg/mL (15-65). Despite the severity of her hypercalcemia she was asymptomatic. She had no past medical history including no prior nephrolithiasis or fractures. Family history was unremarkable. A parathyroid 4D CT and neck ultrasound revealed a 2.7 cm lesion posterior and inferior to the right thyroid lobe and no lymphadenopathy. She underwent parathyroidectomy of the right superior parathyroid gland. Intraoperatively, the right superior parathyroid appeared consistent with an adenoma and dissected easily from the surrounding tissue. The serum PTH declined from 456 pg/mL at baseline to 52 pg/mL 15 minutes after parathyroidectomy.  Histopathology revealed a parathyroid adenoma weighing 2.1 grams and measuring 2.8 x 1.4 x 0.9 cm. Post-operatively, her serum calcium normalized and PTH was 19 pg/mL (15-65). Notably, beginning on post-operative day 2, she experienced fasciculations, muscle cramping, and paresthesias of the extremities despite a serum calcium value in the high normal range. Her symptoms improved with intake of 2000 mg of elemental calcium daily.

Discussion :

Preoperatively, serum calcium ≥14 mg/dL and PTH ≥10-15x the upper limit of normal increase the likelihood of parathyroid carcinoma. If there is suspicion for parathyroid carcinoma it is essential to assess for cervical lymphadenopathy pre-operatively. Given the rarity of parathyroid carcinoma, there is not a standard surgical approach. Focused parathyroidectomy, en bloc resection (including ipsilateral thyroidectomy), and radical surgery (including neck dissection) have been performed. Decision making should be multi-disciplinary and involve an experienced head and neck surgeon. Our case also demonstrates that rapid normalization of serum calcium after prolonged severe hypercalcemia can precipitate symptoms characteristic of hypocalcemia. Treating providers should anticipate this possibility and all patients should receive preoperative counselling regarding this potential transient complication.