Endocrine Abstracts

A 32-years-old lady was admitted with raised calcium. She had palpitation, sweating, 3 stones weight loss and neck swelling. She was diagnosed with Graves’ disease 5 months ago. Her mother had history of thyroid disease but no family history of hypercalcaemia. She had a small goitre and lid lag on examination. On admission, adjusted calcium was 3.04 mmol/l. PTH was < 0.5 pmol/l. Phosphate, vitamin-D, kidney functions, cortisol, myeloma screen and ACE levels were normal. Free T4 was 90.1 pmol/l (NR-11.5-22.7), free T3 >30.8 pmol/l (NR-3.5-6.5) and TSH <0.01 miU/l (NR-0.49-5.43). TRAb antibodies were positive. Ultrasound thyroid showed diffusely enlarged hypervascular thyroid gland. CT chest-abdomen-pelvis showed no malignancy. She was taking Carbimazole 40 mg with good compliance. Hypercalcaemia was treated with IV fluids. Carbimazole was increased to 60 mg and referred for thyroid surgery. Propylthiouracil was tried but not tolerated. She was readmitted a month later with back pain and adjusted calcium 3.17 mmol/l. Despite taking Carbimazole 60 mg, Free T4 was 96.1 pmol/l, free T3 >30.8 pmol/l and TSH <0.01 miU/l. MRI whole spine showed no sinister findings. She was treated with IV fluids and pamidronate. Carbimazole was increased to 100 mg/day in split doses. Surgery was brought forward. She was also given Prednisolone, Lugol iodine and cholestyramine prior to surgery. She underwent total thyroidectomy. She developed post-operative symptomatic hypocalcaemia. She remained stable on Levothyroxine and alfacalcidol.

Learning points

1. Hypercalcaemia occurs in 20% of hyperthyroid patients and usually mild. Severe hypercalcaemia is rarely reported. 2. Pathogenesis of hypercalcemia in thyrotoxicosis is due to increased osteoclast activity mediated by nuclear triiodothyronine receptors. 3. Our case highlights the importance of considering hyperthyroidism as a differential diagnosis for hypercalcaemia. 4. Mainstay of treatment for hyperthyroidism related hypercalcaemia is controlling thyroid status.