FGF23 and Infertility: Both, Fgf23-deficient (Fgf23−/−) and klotho (kl−/−) deficient mice, show a similar phenotype displaying growth retardation, growth plate abnormalities, highly elevated serum phosphate and serum 1,25D3 levels, infertility, arteriosclerosis, premature aging and a shortened lifespan [7]–[8].