Abnormality of urine homeostasis Parathormone-independent increased renal tubular calcium reabsorption Parathormone-independent increased renal tubular Ca2+ reabsorption An increase in the reabsorption of calcium by the renal tubulus that is not associated with increased parathormone levels. This feature is seen with familial hypocalciuric hypercalcemia. This disease has three known genetic etiologies, in type 1 there is a loss of function mutation in the calcium-sensing receptor (encoded by CASR), in type 2 there is a gain of function mutation in GNA11, which is involved in calcium-sensing receptor signaling, and in type 3 there is a mutation in AP2S1, which encodes the adaptor-related protein complex 2, sigma 1 subunit, which alters calcium-sensing receptor endocytosis. Parathormone-independent increased renal tubular Ca reabsorption HP:0003529 UMLS:C4025604