SUN-498 Normocalcemic Tetany: Is Parathyroid Insufficiency a Real Thing?

Abstract

Background: Tetany is characterized by painful flexion of wrist and ankle joints (carpopedal spasm), circumoral numbness and muscle cramps. Increased excitability of peripheral nerves causing tetany is usually due to low ionized calcium. “Normocalcemic tetany” has been reported to be a manifestation of hypomagnesemia, hypokalemia and hyperventilation syndrome. We report a case of normocalcemic tetany in a young woman with a remote history of thyroid surgery. Clinical Case: A 33 year old female with history of total thyroidectomy for a benign nodular goiter presented for evaluation of spells that started 2-3 weeks after total thyroidectomy. Described as a tingling sensation in the neck followed by diffuse muscle cramping, curling of her hands and feet. Each episode lasted 30-60 minutes, 3-4 times a day, 3-4 times a week. These episodes are aggravated by pain, extreme heat and cold, during menstruation, after sexual intercourse and stress. She had irregular contractions with false labor several times during both of her pregnancies. Photographs and videos taken by husband during spells were reviewed and findings consistent with carpopedal spasms. Prior evaluation done by multiple specialtists was negative. Labs showed corrected total calcium 8.5 (8.6-10.3 mg/dL), Ionized calcium 1.25 (1.20-1.40 mmol/L), PTH 30 (12-88 pg/mL), 24 hr urine calcium 206 (100-300 mg/24hrs), 25 hydroxy vitamin D 32.37 (30-100 ng/mL), 1,25 dihydroxy vitamin D 60.4 (19.3-79.3 pg/mL), Phosphorus 3.7 (2.4-4.7 mg/dL) and Magnesium 2.2 (1.8-2.5 mg/dL). Continuous video EEG monitoring showed episodes with opisthotonic posturing, arrhythmic body shaking, hands and feet curling described as nonepileptiform activity. MRI of the whole spine was normal. She is consistently taking Ergocalciferol 50,000 units weekly, Calcium carbonate 1000 mg daily and Calcium carbonate antacid (Tums) as needed. Despite this, she continues to have 1-2 episodes a week. Physical exam showed intermittent bilateral positive Chvostek’s sign. During a recent hysterectomy, she empirically received continuous calcium infusion with maximum Calcium level documented at 9.1 mg/dL. She did not have any episodes for a week after the infusion. This has had a major impact in her life. She is not able to drive and is on disability. She has been recently started on Recombinant PTH (Nat Para) to see if this can eliminate the carpopedal spasms and improve her quality of life. Conclusion: Our patient is being treated as parathyroid insufficiency with relative hypocalcemia from prior total thyroidectomy. The presentation may be subtle with symptoms of hypocalcemia occurring only during metabolic stress, and that a normal serum PTH level in this context may be misleading.