Calhex 231 hydrochloride is primarily used in research settings as a potent and selective antagonist of the calcium-sensing receptor (CaSR). It is widely employed in biochemical and pharmacological studies to investigate the role of CaSR in various physiological and pathological processes. Researchers utilize it to explore calcium homeostasis, bone metabolism, and the regulation of parathyroid hormone secretion. Additionally, it is applied in studies related to diseases such as hyperparathyroidism, osteoporosis, and certain cancers where CaSR signaling plays a critical role. Its high selectivity makes it a valuable tool for dissecting CaSR-mediated pathways and developing targeted therapeutic strategies.