[Extrarenal synthesis of calcitriol in sarcoidosis]

Mean plasma calcitriol was significantly increased in a patient with sarcoidosis and hypercalcemia without elevation of PTH. Recent studies provided evidence for an extrarenal production of calcitriol. To investigate this possibility, the conversion of calcidiol by a sarcoid lymph node homogenate was studied. After 2-hour incubation, a product was present in the incubation, which comigrated with synthetic calcitriol on two high performance liquid chromatography systems, was detected by ultraviolet absorption spectrometry and was bound with high affinity by the chick intestinal receptor for calcitriol. These results provide further evidence for an extrarenal synthesis of calcitriol, contributing to the excessive amounts of this metabolite found in the plasma of patients with sarcoidosis.