Endocrinology & Reproduction · NEET PG Preparation Physiology
A 45-year-old man undergoes a total thyroidectomy for papillary thyroid carcinoma. Four days post-operatively, he complains of perioral numbness, tin…
Practice question from Endocrinology & Reproduction (NEET PG Preparation Physiology), with the correct answer and a step-by-step solution.
medium · MCQ · Q-C32315
A 45-year-old man undergoes a total thyroidectomy for papillary thyroid carcinoma. Four days post-operatively, he complains of perioral numbness, tingling in his fingers, and muscle cramps. On physical examination, tapping the facial nerve anterior to the external auditory meatus results in ipsilateral twitching of the facial muscles. Which of the following intracellular signaling events is primarily responsible for this patient's acute neuromuscular hyperexcitability?
- A.Decreased threshold for sodium channel activation due to reduction in extracellular ionized calciumCorrect answer
- B.Increased intracellular potassium concentration causing continuous membrane depolarization
- C.Blockage of postsynaptic neuromuscular nicotinic acetylcholine receptors
- D.Excessive release of parathyroid hormone from remnant tissue
Solution
Accidental removal or ischemic damage to the parathyroid glands during thyroidectomy leads to hypocalcemia (indicated here by a positive Chvostek sign). Extracellular normally screens the negative charges on the outer surface of cell membranes. A drop in ionized calcium decreases this screening effect, lowering the threshold for voltage-gated sodium channel activation, thereby increasing neuromuscular excitability.
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