There are many symptoms and signs of hypercalcemia, but the main neurological symptoms are fatigue and depression, as in our patient's case. Even when patients are themselves unaware of changes in mental function, family members may remark on subtle loss of mental concentration. Since blood calcium is excreted by the kidney, elevated blood levels increase the risk of stones. The resulting polyuria can cause dehydration, worsening the hypercalcemia. Hypercalcemia decreases gut motility, leading to constipation, nausea, and vomiting.
Vomiting can lead to dehydration and worsen the hypercalcemia.
The electrocardiograpic Q-T interval is shortened by high blood calcium levels, indicating a faster rate of repolarization. Slowed depolarization may give rise to bradyarrythmias. Ventricular hypertrophy has been described, but this may be due to hypertension. Osteitis fibrosa cystica was first described in 1891, but its relation to parathyroid hyperfunction was only discovered in 1925. The most common neurologic symptoms of modern primary hyperparathyroidism are vague and subtle complaints of disturbed mental concentration, fatigue, and memory rather than objective signs of muscle weakness.