Provided herein are methods of treating hypercalcemia in a subject, comprising administering to the subject a therapeutically effective amount of a composition that decreases the expression level and/or activity of GPR64. Compositions comprising the therapeutic agents and methods of screening for agonists and inhibitors of GPR64 are also provided. Compositions and methods for treating primary hyperparathyroidism, secondary hyperparathyroidism, hypoparathyroidism, and osteoporosis without hyperparathyroidism are also provided.