Primary hyperparathyroidism associated with hyperplasia of multiple parathyroid glands in a dog

A nine-year-old Italian Spinone dog presented with a history of urinary incontinence associated with polyuria/polydipsia (PUPD). Haematology and serum biochemistry identified hypercalcaemia. Subsequently, thoracic radiographs, abdominal ultrasound, urinalysis, serum assay of parathyroid hormone (PTH) and PTH-related protein concentrations and ultrasound of the parathyroid glands were consistent with a diagnosis of primary hyperparathyroidism. Unusually, however, all four parathyroid glands were noted to be enlarged on ultrasound, as opposed to a single parathyroid nodule (commonly an adenoma) as is normal in primary hyperparathyroidism. This presented a dilemma as to how best treat the dog; ultimately, two out of four parathyroid glands were removed. Postoperatively, normocalcaemia returned, and PUPD and incontinence resolved. Histopathological examination of the two removed glands was consistent with nodular hyperplasia of chief cells for one gland and nodular hyperplasia of chief cells and oxyphilic cells for the other gland, confirming a diagnosis of parathyroid hyperplasia.