Which electrolyte abnormality is most commonly associated with tetany after thyroid surgery?

• A. Hyperkalemia
• B. Hypernatremia
• C. Hypocalcemia
• D. Hyponatremia

Answer: (C)

Tetany after thyroid surgery is most commonly due to low calcium from impaired parathyroid function. The parathyroid glands regulate calcium levels via parathyroid hormone, which increases bone resorption, renal calcium reabsorption, and activation of vitamin D for intestinal absorption. If the glands are damaged or removed during thyroidectomy, parathyroid hormone falls and calcium drops, making nerve membranes more excitable. That heightened excitability leads to tingling, muscle cramps, and the classic tetany, sometimes with positive Chvostek or Trousseau signs. Other electrolyte issues—like high potassium or abnormal sodium—don't typically produce the same tetany picture in this post-surgical setting.