Indeed, in a pre-clinical study of mice with and without experimental CKD fed an iron-deficient diet, whole bone Fgf23 mRNA expression and plasma concentrations of total (intact + fragmented) FGF23 increased to a similar degree in both the non-CKD and CKD groups, but the increase in plasma concentrations of full-length, intact FGF23 was much greater in the mice with CKD [44]. The gene discussed is FGF23; the disease is chronic kidney disease.