Endocrine Abstracts

Case history: A 34-year old Caucasian nurse presented to her GP with a 7 month history of abdominal pain. She was found to have PTH-dependent hypercalcaemia with Stage 3A chronic kidney disease (corrected calcium 3.43 mmol/l, phosphate 0.62 mmol/l, total vitamin D 32 nmol/l, PTH 214.9 pmol/l, creatinine 117 μmol/l and eGFR 45 ml/min/1.73m²). On direct questioning, she reported fatigue, generalised weakness and intermittent joint pains affecting her lower back and both hips. She had no past medical history and did not take any prescribed or over-the-counter medication. There was no history of malignancy or endocrinopathy in her family.

Investigations: Following urgent referral to otolaryngology, computerised tomography (CT) and ultrasound demonstrated a 25 × 17 × 23 mm left inferior parathyroid lesion. She was diagnosed with severe primary hyperparathyroidism and due to high PTH, parathyroid carcinoma was suspected. There was no evidence of renal calculi on ultrasound. Thyroid function, plasma metanephrines and calcitonin were all normal.

Results and treatment: Oral colecalciferol was commenced and she was admitted for intravenous fluids prior to a left inferior parathyroidectomy and thymectomy, two months after presentation to her GP. Her post-operative course was complicated by mild hypocalcaemia attributed to Hungry Bone Syndrome, treated with alfacalcidol and elemental calcium. Genetic screening for familial primary hyperparathyroidism was negative. Parathyroid histology was consistent with low grade parathyroid carcinoma with multifocal vascular and capsular invasion. Ki67 index was 3%. Thymus histology was benign. Her post-operative staging CT demonstrated multiple large lytic bone lesions replacing her T9 vertebra, right femoral neck and two pelvic lesions all concerning for metastases or brown tumours. There were no other lesions or lymphadenopathy on CT. Magnetic resonance imaging confirmed hypodense lesions on T1 and bright cystic lesions on T2 – typical for brown tumours. She has been referred for urgent bone biopsy and orthopaedic stabilisation of her right hip and T9 vertebra. She will remain under close follow up with the Endocrinology team.

Conclusions and points for discussion: This is a very rare presentation of parathyroid carcinoma in young person with no associated genetic condition. Parathyroid carcinoma should always be considered in primary hyperparathyroidism with markedly elevated PTH. Brown tumours are bone lesions that occur in relation to excess osteoclast activity and are a type of osteitis fibrosa cystica. Although not neoplastic they can cause skeletal instability and fractures. They are an important potential sequalae of severe long-standing hyperparathyroidism so patients should be counselled appropriately and investigated promptly should they develop focal pain.