FHH, HHM, MEN2, familial hyperparathyroidism syndromes (rare), lithium toxicity, mild Jansen syndrome (Moroccan Jews, extreme manifestation, receptor constituitively active). MEN1: hyperparathyroidism (90% most common manifestation), PPP syndrome (pancreatic tumors, gastrinoma, pituitary tumors). Hypercalcemia due primarily to bone resorption. Most important form of HPT, congenital, autosomal dominant, sometimes sporadic, increased parathyroid set-points from activation of CaR mutations. Asymptomatic: sometimes complain of easy fatiguability, weakness, concentration disturbances, polydipsia. Hypercalcemia, hypophosphatemia, hypermangesemia, normal or slightly elevated PTH and 1,25D, low Ca clearance compaired to creatinine in 80% of patients. No treatment indicated. Defined role in fetuses, organogenesis of certain tissues (heart, skeleton, echondral bones, mammary glands, heart, hair follicles, etc.). Alternate splicing from PTH. Partially resemble N-terminal end of PTH. Calciotrophic hormone during fetal life and during lactation. In adults, expressed in: mammary glands, skin, hair, smooth muscle, placenta, CNS.