A 31-year old male presented with bone pain, polyuria and a palpable nodule in the neck. Radiological examination showed generalised osteopenia, subperiosteal erosion and presence of bilateral renal stones. The essential chemical pathological changes were increased plasma calcium, mid-molecule immuno-reactive parathyroid hormone (iPTH), human chorionic gonadotrophin (hCG) levels. Surgical excision of the nodule revealed a parathyroid carcinoma. The uniqueness of this case is the steroid-suppressible plasma calcium, iPTH, and hCG levels. The diagnostic implications of the findings are discussed.