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Editor,—Although medical intervention can be deleterious when diabetes mellitus coexists with other endocrinopathies, as shown by increased susceptibility to insulin related hypoglycaemia in the case reported above,1the converse is also true that treatment of metabolic crisis can occasionally prove to be equally beneficial for diabetic decompensation and for coexisting unsuspected endocrinopathy other than Addison's disease. This is illustrated by an 81 year old woman admitted with diabetic decompensation characterised by a plasma glucose concentration of 35.1 mmol/l, urea 32.2 mmol/l, creatinine 164 μmol/l, and bicarbonate 24 mmol/l, in the presence ofEscherichia coli septicaemia. By day 17, as a result of treatment with intravenous fluids, insulin infusion, and antibiotics, she was much improved, with random blood glucose of 3.1 mmol/l, urea 8.9 mmol/l, creatinine 142 μmol/l, and she was subsequently discharged home. What had been overlooked, in the preoccupation with her diabetic status, was that plasma calcium concentrations on day 1 and on day 17 were 3.6 mmol/l, and 2.64 mmol/l, respectively (unsolicited, therefore not perceived!), and that emergency treatment of diabetes, using large amounts of intravenous fluids, had been of equal benefit for diabetes and for coexisting hypercalcaemia. The latter, on subsequent investigation, proved to be attributable to primary hyperparathyroidism (characterised by a serum parathyroid hormone level of 75 pg/ml (reference range 11–55 pg/ml), in the presence of a plasma calcium of 2.94 mmol/l, with concurrent plasma albumin of 30 g/l).
The prevalence of diabetes mellitus may be as high as 7.8% among patients with proven primary hyperparathyroidism,1-2 either as a result of the fact that, since both type 2 diabetes and primary hyperparathyroidism are age related,1-3 1-4 their prevalence in old age might be sufficiently high to result in their coexistence by pure chance, or because hypercalcaemia can be complicated by insulin resistance.1-5 Support for the latter theory comes from the case report of a 56 year old woman presenting simultaneously with type 2 diabetes and primary hyperparathyroidism, in whom parathyroidectomy resulted in reversal of glucose intolerance. This therapeutic “coup” was validated by the fact that, postoperatively, having discontinued her antidiabetic medication (gliclazide) for three months as a result of excellent control (characterised by glycated haemoglobin of 4.6%), a subsequent 75 g oral glucose tolerance test yielded normal results.1-6