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Radiology of HyperParaThyroidism

- Findings:
    - Assymmetrical osteopenia;
    - Spine: vertebral compression fractures;
    - Skull:
         - so-called salt-and-pepper skull
         - tiny punched out lesions may be present in the skull, producing so called salt and pepper appearance;
    - Clavicle: erosion of the outer centimeter of the clavicle
    - Tibia: marked osteopenia of the medial aspect of the tibia
    - Phalanges:
         - subperiosteal resorption of digital tufts and phalanges (which is usually more marked on radial than on
                  ulnar side of the hand);
         - look for resorption of phalangeal tufts and replacement of usually sharp cortical outline of bone in digits
                  by irregular outline (subperiosteal resorption);
         - ref: Images in Clinical Medicine. Subperiosteal Bone Resorption

- Brown Tumors:

     - occurs in severe cases;
     - referred to as "Giant Cell Tumor of Diaphysis"
     - microscopical exam revealed that it was composed of numerous osteoclasts with stromal hemorrhage;
     - ref: A case of multiple skeletal lesions of brown tumors, mimicking carcinoma metastases

- Soft Tissues Calcification: (see: diff dx)
     - occurs due to increase in serum calcium & serum phosphate (seen in secondary HPT);
     - special sites of affinity for calcification include triangular ligament in the distal radio-ulnar articulation, menisci, and
              articular cartilages;
     - chondrocalcinosis can be seen by itself in elderly and has been associated with chronic disorders such as osteoarthritis,
              rheumatoid arthritis, diabetes mellitus, hypertension, hyperthyroidism, acromegaly, and Paget's disease;

- Bone:
    - mobilizes bone and phosphate;
    - releases osteocytic perilacunaar stores (fast)
    - increases osteocytic number and activity (slow)
    - activating and increasing number of osteoclasts, which destroys hydroxyapatite, thus releasing calcium and phosphate