Protein kinase B PKB/Akt and SGK isoforms have previously been shown to participate in the regulation of renal tubular calcium and phosphate transport. PKB/Akt and SGK dependent signaling involves phosphorylation and thus inactivation of glycogen synthase kinase GSK3. The present study explored, whether PKB/SGK dependent GSK3 activity participates in the regulation of mineral metabolism. To this end, experiments have been performed in mutant mice, in which PKB/SGK-dependent GSK3a,ß regulation is disrupted by replacement of the serine in the respective SGK/PKB-phosphorylation consensus sequence by alanine (gsk3^KI). Those mice were compared to their wild-type littermates (gsk3^WT). Plasma phosphate concentration was significantly lower and plasma Ca²⁺ concentration tended to be lower in gsk3^KI than in gsk3^WTmice. Despite the lower plasma concentrations, urinary excretion of both, phosphate and Ca²⁺ were significantly higher in gsk3^KI than in gsk3^WTmice. The plasma concentrations of both, PTH and 1,25(OH)₂D₃ were significantly lower in gsk3^KI than in gsk3^WTmice. Similarly, bone density was significantly lower in gsk3^KI than in gsk3^WTmice. The present observations disclose a novel powerful signalling pathway in the regulation of renal calcium and phosphate excretion and bone mineralization.