A 64-year-old female presented to the acute medical take with hypercalcaemia. She had a 3 weeks history of polyuria, polydipsia, constipation, intermittent abdominal pain and feeling depressed. She reported weight loss of 3.5 kg over the past 6 months. She denied symptoms of dysphagia, dyspnoea, haemoptysis, haematemesis, or malaena. Her past medical history included anaemia, ischaemic heart disease, chronic obstructive pulmonary disease and uterine prolapse. She was an ex-smoker with 45 pack-year history. She drank ten units of alcohol. Investigations revealed: corrected calcium, 3.35 mmol/l; PTH, 28.9 pmol/l; vitamin D, 39.4 μg/l, and normal glucose and U&Es. Parathyroid sestamibi scan showed focal uptake in the inferior left thyroid lobe. Initial diagnosis of Primary hyperparathyroidism was made but the parathyroidectomy showed a likely parathyroid carcinoma but without all features of cancer. Two months later, her symptoms of polyuria and polydipsia returned but had normal calcium and PTH levels. However, her blood glucose level was 49.1 mmol/l (HbA1c, 145 mmol/mol). Her BMI was 23. She was started on basal bolus insulin regime. Four months later, her insulin requirements decreased dramatically (Novorapid two units BD and Glargine four units; HbA1c, 46 mmol/mol) and was stopped. Ten months later she was still off insulin with a HbA1c of 43 mmol/mol.
It is known that both high PTH and hypercalcaemia can increase insulin resistance resulting in compensatory hyperinsulinaemia. While transient reduction in insulin secretion has been demonstrated in post-parathyroidectomy patients, onset of insulin requiring diabetes has never been reported in the literature. Our patient clearly demonstrates the relative insulin deficiency following parathyroidectomy resulting in diabetes. It highlights the need for close monitoring of glucose level in post-parathyroidectomy patients, especially if they had prolonged high calcium and PTH levels prior to surgery.