Endocrine Abstracts

Case: A 56-year-old patient was referred to our endocrinology unit for management of severe hypercalcemia. He had complained initially from asthenia, intractable nausea and vomiting and weight loss (10 kg), but now also suffered from polyuria-polydipsia, bradypsychia and bradylalia, and diffuse joint pain with loss of strength in the lower limbs. Initial laboratory investigations showed a parathyroid crisis with marked increases of parathyroid hormone (PTH) at 2138.5 pg/ml (45×ULN), calcemia at 4.75 mmol/l (2.10–2.55), and urinary calcium excretion at 714 mg/24 h. The patient had severe acute renal failure (AKIN 3), nephrolithiasis, and osteoporosis, with a fracture of the radial pallet occurring 8 weeks before admission.

Further investigations revealed a 6 cm right para-mediastinal mass responsible for a left tracheal deviation on chest X-ray. This was confirmed by cervical ultrasound and cervico-thoracic CT which showed a predominantly cystic mediastinal mass with no evidence of parathyroid adenoma in orthotopic position. There was also a goiter with multiple non-suspect infracentimetric nodules. The parathyroid scintigraphy showed intense uptake of MIBI in the antero-superior portion of the mass, corresponding to the solid part, without other uptake. Given the persistence of severe hypercalcemia after treatment by intravenous hydration and furosemide, the patient received a pamidronate infusion leading to a rapid reduction in serum calcium to 2.6 mmol/l 24 hours before en-bloc resection of the mass by sternotomy. Pathological analysis revealed a parathyroid carcinoma with apparent R0 resection.

In the early postoperative period, the occurrence of a hungry bone syndrome required massive calcium and vitamin D substitution, which was progressively reduced and withdrawn 10 months postoperatively. After 2 years, hypercalcemia progressively recurred (from 2.56 to 2.83 mmol/l) with PTH remaining in the normal range. A relapse or extension of the parathyroid carcinoma was first suspected.

However, a new cervico-thoracic CT scan and 18 FDG PET scan showed no recurrence or residual tissue at the site of first resection or distally. A parathyroid scintigraphy identified abnormal uptake adjacent to the superior-medial pole of the left thyroid lobe, suggesting the presence of a parathyroid adenoma at this level. This single localisation was confirmed by PET methionine. A significant PTH gradient was also observed in the left superior cervical vein at selective venous sampling. The patient underwent cervical exploration with selective resection of a left superior parathyroid adenoma of 20x12x7 mm, without evidence of malignancy at pathological examination. This second surgery led to a sustained normalization of calcemia.

Discussion: We report the case of a patient with a double parathyroid pathology: a large right mediastinal parathyroid carcinoma followed by a benign left parathyroid adenoma which was diagnosed two years later. Parathyroid carcinoma is a rare cause of hyperparathyroidism with an incidence of 0.3 to 2.1%¹. This large malignant tumour induced a severe parathyroid crisis, which nowadays accounts for less than 10% of the initial clinical manifestations, whereas renal and bone involvements are respectively found in 32–80% and 34–91% of cases^2,3. The recommended treatment is surgical and should consist in a total en-bloc resection^3,4. Chemotherapy and radiotherapy give disappointing results³, while immunotherapy may prove beneficial but inconsistently⁵. The post-operative evolution was marked by a hungry bone syndrome, as it can occur classically after parathyroidectomy for severe and longstanding hypercalcemia⁶. The evolution was also complicated by the lack of long-term calcium normalisation which raised suspicion of a cancer relapse, but finally led to the diagnosis of the benign parathyroid adenoma.

References: 1. Ozolins A et al. Evaluation of malignant parathyroid tumours in two European cohorts of patients with sporadic primary hyperparathyroidism. Langenbeck’s Archives of Surgery, 401(7), (2015) 943–951.

2. Shane E. Bilezikian JP. Parathyroid carcinoma: a review of 62 patients. Endocrine Reviews, 3(2), (1982) 218–226.

3. Shane E. Parathyroid carcinoma. The Journal of Clinical Endocrinology and Metabolism 86(2), (2001) 485–493.

4. Owen RP. et al. Parathyroid carcinoma: a review. Head & Neck 33(3): (2011) 429–36.

5. Betea D, Potorac I, Beckers A. Parathyroid carcinoma: Challenges in diagnosis and treatment. Ann Endocrinol (Paris) 76(2), (2015) 169–177.

6. Brasier AR, Nussbaum SR. Hungry bone syndrome: Clinical and biochemical predictors of its occurrence after parathyroid surgery. The American Journal of Medicine, 84(4), (1988) 654–660.