The relation between gastrointestinal organs and bone metabolism has become clearer during the last decades. Of paramount importance is the tight and intertwined regulation of gastric acid secretion and bone metabolism in regard of diseases caused by dysfunction of any of these or intermediary organs or mediators. The importance of the functions of the endocrine modulators 1,25(OH)2 vitamin D (calcitriol), PTH, and calcitonin becomes clear when seeing misbalances and its impact on the skeleton. Another important player in the gut-bone signaling axis is calcium, which is operating through the calcium-sensing receptor (CaSR). The CaSR is located on diverse tissues of the human body, such as the parathyroid glands, stomach, intestine, and kidney. The strict regulation of calcium homeostasis is of high importance and any disturbances have immense consequences for the body. Mechanisms and therapeutic implications, as well as diseases caused by imbalances on the stomach-bone signaling axis, are highlighted in the following chapter.
Keywords: CaSR; Calcium; Gastric acid; Gastrointestinal tract; Ionic homeostasis; Osteoporosis; PPI; PTH; Skeleton; Vitamin D.