Define Post-Thyroidectomy Hypocalcaemia. Describe its clinical features and management.

The Mechanism

Hypocalcaemia is an important early complication of thyroid (and parathyroid) surgery, and its cause is anatomical: the four tiny parathyroid glands, which control calcium via parathyroid hormone (PTH), lie immediately behind the thyroid and may be inadvertently removed or, more often, devascularised during thyroidectomy. The resulting hypoparathyroidism lowers serum calcium, typically appearing at 24–72 hours post-operatively as the effect declares itself.

Clinical Features

Low ionised calcium increases neuromuscular excitability, producing the classic picture: perioral tingling and paraesthesiae of the fingers and toes, muscle cramps, and carpopedal spasm, progressing in severe cases to tetany, laryngospasm and seizures. Two eponymous bedside signs support the diagnosis: Chvostek's sign (twitching of the facial muscles on tapping over the facial nerve) and Trousseau's sign (carpal spasm when a blood-pressure cuff is inflated above systolic for a few minutes). The ECG may show a prolonged QT interval.

Management

Serum calcium is checked routinely after thyroidectomy. Mild hypocalcaemia is treated with oral calcium supplements and vitamin D (an activated form such as alfacalcidol); symptomatic or severe hypocalcaemia (tetany, laryngospasm) is a medical emergency treated with slow intravenous calcium gluconate with cardiac monitoring. Most cases are transient (the bruised glands recover), but hypoparathyroidism can be permanent after total thyroidectomy, requiring long-term calcium and vitamin D.

Parathyroid Preservation

The best treatment is prevention: during thyroidectomy the surgeon carefully identifies the parathyroid glands and preserves their delicate blood supply, and auto-transplants any gland that is inadvertently removed or devascularised (implanting it into a neck or forearm muscle, where it can re-establish function). This is why permanent hypoparathyroidism, though feared, is uncommon in experienced hands, and most post-operative hypocalcaemia recovers as the bruised glands resume working.

Monitoring & the Permanent Case

Serum calcium is monitored serially after total thyroidectomy (often with PTH), because the nadir may occur at 24–72 hours. Transient hypocalcaemia is treated until the bruised parathyroids recover, but permanent hypoparathyroidism requires lifelong calcium and activated vitamin D (e.g. Alfacalcidol or calcitriol), with periodic monitoring to avoid over-treatment and renal complications. Prevention — careful parathyroid identification and auto-transplantation of a devascularised gland — is far better than cure, which is why gland preservation is a central aim of the operation.

The Bottom Line

The take-home message is that post-thyroidectomy hypocalcaemia is common, usually transient, and readily treated once anticipated — which is why calcium is checked routinely, symptoms of tingling and spasm are watched for, and parathyroid preservation (with auto-transplantation when needed) is a deliberate part of the operation.

Perioral tingling is the earliest symptom — check calcium promptly.

• Parathyroid glands (behind the thyroid) are removed/devascularised → hypoparathyroidism → low calcium at 24–72 h.
• Features: perioral tingling, paraesthesiae, carpopedal spasm, tetany/laryngospasm; Chvostek's and Trousseau's signs; long QT on ECG.
• Check calcium routinely post-thyroidectomy.
• Treat: oral calcium + vitamin D (alfacalcidol); severe/symptomatic → IV calcium gluconate with monitoring.
• Usually transient; can be permanent after total thyroidectomy.