FGF23 and subarachnoid hemorrhage: In the past decade, FGF23 has emerged as a possible marker (both diagnostic and prognostic) and therapeutic target in several conditions: hereditary diseases (syndromes of FGF23 excess and syndromes of FGF23 deficiency; hypophosphatemic and hyperphosphatemic disorders), acute renal failure and chronic kidney disease, stroke and subarachnoid hemorrhage, several types of neoplasms, psoriasis, gestational diabetes mellitus (DM), diabetic nephropathy, and bone metabolic disease and preclinical disease in type 2 DM [1-3].