A 37-year-old woman with paresthesia in fingertips, toes and lips; stomach cramps; dry skin and nails breaking. Diagnosis?

• A. Hyperparathyroidism
• B. Hypothyroidism
• C. Hypoparathyroidism
• D. Addison's disease

Answer: (C)

Hypocalcemia from hypoparathyroidism causes neuromuscular excitability that explains these symptoms. When parathyroid hormone is low, calcium levels fall and phosphate rises. Low extracellular calcium makes nerve and muscle membranes more likely to depolarize, producing tingling and numbness around the mouth and in the fingers and toes, cramps, and sometimes tetany. GI smooth muscle irritation can manifest as stomach cramps. Calcium is also important for skin and nail health, so dry skin and brittle nails can accompany hypocalcemia.

This pattern fits hypoparathyroidism best because the combination of perioral and distal paresthesias with cramps and skin/nail changes aligns with low calcium. Other conditions would present differently: high calcium from hyperparathyroidism tends to cause fatigue, bone pain, kidney stones, and hypercalcemic features rather than the described neuromuscular symptoms; hypothyroidism mainly causes fatigue, weight gain, cold intolerance, and dry skin but not the specific paresthesias; Addison’s disease presents with fatigue, weakness, hypotension, hyperpigmentation, and electrolyte abnormalities rather than this paresthesia-cramp combination.