Hypoparathyroidism

A post-thyroidectomy patient develops tingling around the mouth and fingertip numbness within 24 hours. The calcium crash has begun — and you have minutes to act on assessment findings that confirm it.

Hypoparathyroidism results from insufficient parathyroid hormone (PTH), most commonly after accidental removal or damage to the parathyroid glands during thyroid or neck surgery. Without PTH, serum calcium drops (hypocalcemia < 8.5 mg/dL) and serum phosphorus rises (hyperphosphatemia > 4.5 mg/dL) — this inverse relationship is the hallmark. Early symptoms are neuromuscular: perioral tingling, numbness in fingers and toes, and muscle cramps. As calcium falls further, tetany develops — carpopedal spasm, laryngospasm, and potentially seizures. Two bedside assessments confirm neuromuscular irritability: Chvostek's sign (tapping the facial nerve anterior to the ear produces ipsilateral facial twitching) and Trousseau's sign (inflating a BP cuff above systolic for 3 minutes triggers carpal spasm — the hand flexes into a characteristic posture). Trousseau's is more specific and more reliable. Acute management includes IV calcium gluconate administered slowly with cardiac monitoring, because rapid infusion risks cardiac arrest. Long-term management involves oral calcium supplements and active vitamin D (calcitriol) to maintain absorption, since PTH is no longer stimulating vitamin D activation in the kidneys.

Key Distinctions

Don't confuse hypoparathyroidism (low calcium, high phosphorus, tetany, hyperreflexia) with hyperparathyroidism (high calcium, low phosphorus, lethargy, hyporeflexia) — they are clinical opposites. Students mix up Chvostek's (face tap → facial twitch) with Trousseau's (BP cuff → hand spasm). Remember: Trousseau's uses a tourniquet-like device. Calcium gluconate is the IV rescue drug — not calcium chloride, which causes tissue necrosis if it infiltrates.

Clinical Pearl

Post-thyroidectomy, keep a tracheostomy tray AND IV calcium gluconate at the bedside. Laryngospasm from hypocalcemia can close the airway before any lab result prints.