IS case 453: Secondary hyperparathyroidism
Imaging Sciences URMC 2010
Publication Date: 2010-08-30
Secondary hyperparathyroidism represents a hormonal response hyperphosphatemia. Phosphate is a parathyroid hormone (PTH) stimulator and 25-hydroxyvitamin D-->calcitriol catalase inhibitor. Elevated PTH levels normally increase phosphate renal clearance, however reduced glomerular filtration rates in renal failure may limit this effect. Elevated PTH also increases bone calcium resorption and low vitamin D levels decrease gastrointestinal calcium absorption, further stimulating bone resorption.
Hyperparathyroidism of the skull manifests as diffuse focal areas of lytic resorption in the bony trabeculae and as cortical thinning without expansion. Paget's disease diffusely involves the skull, but is expansile. Multiple myeloma can cause multiple lytic lesions, but is inhomogeneous with less diffuse resorption of trabecular and cortical bone. This pattern of dark focal lytic lesions mixed with high attenuation trabeculae is termed a "salt and pepper" appearance on CT.
Additional pulmonary manifestations of hyperparathyroidism can further establish a radiographic diagnosis. Chest films show resorption of the distal clavicle with apparent acromioclavicular (AC) joint distraction. Elevated phosphate levels cause calcium phosphate formation with deposition throughout the body. This leads to extensive calcification of all vessels including small vessel calcifications that can cause pulmonary artery hypertension and cardiac enlargement. Intraparenchymal metastatic calcium phosphate deposition presents as nodular interstitial opacification of the mid/lower lung zones, although not seen in this case.
All of these findings exemplify radiographic signs of hyperparathyroidism.
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