In a 3 3-year-old woman concurrence of a complete distal renal tubular acidosis (RTA) and lymphocytic thyroiditis with spontaneously resolving hyperthyroidism was observed. Until recently, the rare association of RTA and hyperthyroidism had been thought to be governed by nephrocalcinosis, via hypercalcemia and hypercalciuria. However, in this case, nephrocalcinosis was not present, but there were histological signs of renal interstitial mononuclear cell infiltration, and the RTA persisted despite the resolution of the hyperthyroidism. This observation supports the idea that immunological mechanisms may relate RTA and hyperthyroidism when the latter has an autoimmune origin.

Immunoreactive parathyroid hormone (PTH) levels and nephrogenous cyclic adenosine monophosphate (cAMP) have been reported to be useful parameters in the diagnosis of hyperparathyroidism. Measurements in hyperparathyroid patients usually give values above the normal range when PTH is measured with a carboxyterminal radioimmunoassay and when nephrogenous cAMP is related to glomerular filtration rate. We tested these two parameters in two groups of hypercalcaemic patients (twelve cases of primary hyperparathyroidism and fourteen cases of hypercalcaemia of non-parathyroid origin) and in two groups of normocalcaemic subjects (twenty-one young healthy volunteers and fourteen elderly subjects without parathyroid disease). Slight impairment of renal function caused elevated values of immunoreactive parathyroid hormone in a carboxyterminal radioimmunoassay and also of nephrogenous cAMP when related to glomerular filtration rate. We found that elevated nephrogenous cAMP without parathyroid disease could be attributed to renal insufficiency and to the mode of expression generally used for the nephrogenous cAMP.