Spontaneous remission of severe hyperparathyroidism with normalization of the reversed whole PTH/intact PTH ratio in a haemodialysis patient.

Secondary hyperparathyroidism is one of the most common and serious abnormalities in patients with chronic kidney disease. Despite recent progress in the treatment of hyperparathyroidism, advanced uraemic nodular hyperplasia, or rarely, sporadic primary adenoma accompanied by chronic renal failure is usually resistant to medical treatment and requires parathyroidectomy [1,2]. Spontaneous remission of hyperparathyroidism is a very rare complication, either primary or secondary, especially in patients on dialysis. The aetiology of spontaneous infarction has not been elucidated, but excessive tissue growth may well be one of the most clinically relevant factors, because a large parathyroid gland is susceptible to ischaemic insult [3]. For the management of hyperparathyroidism in chronic kidney disease, second-generation PTH assays, such as intact PTH assay, have been widely used [4]. However, these assays react not only with full-length PTH (1–84), but also with large C-terminal fragments, mostly PTH (7–84). The newly developed third-generation PTH assays, such as whole PTH assay, are more sensitive and specific when measuring bioactive PTH (1–84) [5]; therefore, PTH values obtained with second-generation assay are generally higher than those obtained with third-generation PTH assay [6]. Rare exceptions to this rule, however, have been reported in severe primary or secondary hyperparathyroidism and parathyroid carcinoma [7–10]. We present here a case of a haemodialysis patient with severe hyperparathyroidism, in whom abnormally higher whole PTH levels than intact PTH levels normalized after