What is elevated when Trousseau's sign is positive?

When Trousseau's sign is positive, it indicates a deficiency or imbalance in calcium levels, particularly hypocalcemia. Trousseau's sign is elicited by inflating a blood pressure cuff on the arm to a pressure above systolic for a few minutes, which can result in carpal spasm. This response is due to increased neuromuscular excitability associated with low calcium levels in the blood, reflecting a state where calcium is not sufficiently available for the proper function of neurotransmission and muscle contraction.

Elevated calcium levels, on the other hand, would not provoke the same neuromuscular irritability, highlighting the critical role calcium plays in maintaining muscle and nerve function. Recognizing Trousseau's sign as a sign of low calcium assists in diagnosing conditions such as parathyroid dysfunction or vitamin D deficiency, which are directly linked to calcium metabolism.