Calcium homeostasis maintenance is controlled by calciotropic hormones action. Bone is a major target tissue for PTH and calcitriol. Excess in at least one of two hormones may be deleterious to bone, leading to osteoporosis. Calciotropic hormones must of course be measured if an anomaly of serum calcium/phosphate is discovered. However, when the degree of osteopenia is discordant with the risk factors of osteoporosis in a given patient, it may be of value to measure calciotropic hormones, even if serum calcium/phosphate are normal. Previously undiscovered cause(s) for secondary osteoporosis may be diagnosed which, if untreated, may impair the efficacy of antiresorptive treatments (estrogens, biphosphonates, ...). Whether to measure calciotropic hormones or not in other less-defined groups of osteoporotic patients remains both debatable and debated.