TRPM6 and familial primary hypomagnesemia: Currently there are two suggested mechanistic models of hypomagnesemia in humans carrying mutations in TRPM6. A pioneering study of patients with congenital hypomagnesemia anticipated that Mg2+ malabsorption in the intestine plays a key role in organismal Mg2+ deprivation (Friedman et al., 1967; Milla et al., 1979).