Examines the molecular basis for altered signal transduction in patients with disordered G protein function (e.g. pseudohypoparathyroidism type 1a and McCune Albright syndrome), patients with abnormal PTH receptor function (e.g. pseudohypoparathyroidism type 1b), and patients with abnormal PTH function (e.g. Familial Isolated Hypoparathyroidism).