Hypoparathyroidism and coeliac disease: a potentially dangerous combination

Hypoparathyroidism and co-existing coeliac disease can lead to dramatic fluctuations in plasma calcium levels, a therapeutic challenge doctors should be aware of. Acquired hypoparathyroidism is usually the result of surgery and is estimated to occur in 0.5–6.6% of patients following total thyroidectomy, with an even higher rate in some case series, but a lower rate in endocrine surgical centres, where it ranges from 0.9% to 1.6%.1–4 The occurrence of hypoparathyroidism depends on the surgeon's experience, the extent of thyroid resection and the underlying thyroid disease, with the presence of substernal goitre, cancer or Graves' disease increasing the risk.5 Hypoparathyroidism may also occur secondary to autoimmune invasion and destruction of the parathyroid gland, as in polyglandular syndrome type 1. In comparison, coeliac disease has a high prevalence of 1:300 in white Caucasians of northern European ancestry.6 Both these conditions lead to hypocalcaemia. When calcium levels in a previously stable treated patient with hypoparathyroidism decrease or begin to fluctuate significantly, the differential diagnosis includes prolonged use of laxatives or anticonvulsant therapy, chronic renal failure, decreased dietary intake of calcium and Vitamin D or malabsorption such as occurs with coeliac disease. On the other hand, the institution of and adherence to a gluten-free diet in a newly-diagnosed patient with coeliac disease on Vitamin D may lead to rapid improvement of intestinal absorption with prompt increases in plasma calcium levels. Here we present two patients diagnosed with hypoparathyroidism, both of whom went on to develop coeliac disease at a later stage. Profound alterations in calcium balance occurred before and after the diagnosis of coeliac disease, which serves to illustrate the changes in calcium levels that may result from the combination of hypoparathyroidism and coeliac disease, and to alert us to the potential complications of this combination of pathologies.