HNF1B and familial primary hypomagnesemia: HNF1B-associated hypomagnesemia is associated with altered transactivation of the gamma-subunit of the Na+-K+-ATPase in the distal convoluted tubule (DCT), which regulates epithelial ion transport.6, 10 Impaired general transport activity in the DCT is usually associated with a Gitelman-like tubulopathy, consisting of hypokalemic hypochloraemic alkalosis with hypocalciuria, in addition to hypomagnesemia.11