Hyperparathyroidism secondary to parathyroid hyperplasia in a cat

An 11-year-old neutered male domestic shorthair cat was incidentally diagnosed with hypercalcemia during routine wellness screening. Subsequent workup revealed elevated ionized calcium, increased parathyroid hormone concentrations, and undetectable parathyroid hormone-related peptide, consistent with a diagnosis of primary hyperparathyroidism. Cervical ultrasound revealed a left parathyroid nodule, and the cat underwent a left cranial parathyroidectomy without intraoperative or postoperative complications. Histopathology was consistent with parathyroid hyperplasia. At the time of writing (> 1100 d after diagnosis), the cat was clinically well, with normal total and ionized calcium, and had not required calcium supplementation. Key clinical message: Only a few cases of feline primary hyperparathyroidism are described in the literature. Most previously published case reports described cats evaluated for clinical signs attributable to hypercalcemia. In contrast, this case was identified during a routine wellness examination in an asymptomatic cat. This emphasizes the importance of preventive care and demonstrates that routine wellness screening can facilitate early detection of subclinical disease, enabling timely intervention and contributing to improved long-term outcomes.