PRIMARY HYPERPARATHYROIDISM Primary hyperparathyroidism is a rare endocrine disorder in cats. Probable primary hyperparathyroidism has been described in a cat with polyostotic lesions1. Lesions involve particularly the axial skeleton, including the cranial vault, mandible, and sternebrae. The appendicular skeleton was involved to a lesser extent. Cervical and thoracic intervertebral and diarthrodial joints had collapsed. Bone lesions appear to be uncommon, however, and have not been described in other cats with primary hyperparathyroidism2.