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Post-Thyroidectomy Hypocalcaemia — FRCA Final MCQ

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EasyGeneral AnaesthesiaPost-Thyroidectomy HypocalcaemiaFRCA Final

A 46-year-old woman undergoes an uncomplicated total thyroidectomy without blood transfusion. Six hours later, she develops perioral tingling and carpopedal spasm and has a positive Chvostek sign. Her corrected serum calcium concentration is 1.62 mmol/L; it was normal preoperatively. What is the most likely underlying cause?

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Correct answer: E — Loss of parathyroid function after removal or devascularisation

The correct answer is E. Total thyroidectomy may inadvertently remove the parathyroid glands or compromise their delicate blood supply, producing transient or permanent hypoparathyroidism. Reduced PTH decreases renal calcium retention and renal calcitriol production and reduces mobilisation of calcium from bone, causing hypocalcaemia. The rapid fall in ionised calcium increases neuromuscular excitability, producing perioral paraesthesia, carpopedal spasm and Chvostek sign. Superior or recurrent laryngeal nerve injuries cause voice, swallowing or airway abnormalities rather than hypocalcaemia. Citrate can chelate ionised calcium during major blood transfusion, but no blood products were administered. Vitamin D deficiency may cause hypocalcaemia but would not best explain this abrupt postoperative presentation with normal preoperative calcium.

Reference: North Tees and Hartlepool NHS Foundation Trust. Parathyroid Gland and Calcium after Total Thyroid Surgery, section 'Parathyroid Glands following Surgery', 2026. https://www.nth.nhs.uk/resources/parathyroid-gland-and-calcium-after-total-thyroid-surgery/