A 41-year-old asthmatic woman presented to our emergency department exhibiting symptoms of lethargy, respiratory distress, and tachycardia. Baseline laboratory investigation revealed a significantly elevated theophylline level as well as marked hypercalcemia (calcium = 16.0 mg/dL). Serum calcium normalized after theophylline was discontinued. The unusual level of hypercalcemia secondary to theophylline toxicity may have been related to the action of beta agonists (used in conjunction with theophylline to treat bronchospasm), dehydration, or concomitant mild hyperthyroidism. Suppressed parathyroid hormone (PTH) and 1ndash;25 dihydroxy vitamin D levels measured in our patient suggest a mode of action for theophylline-induced hypercalcemia that is completely independent of PTH action.
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