Osteopenia regressed completely following treatment The main raison d'etre of parathormone is to increase the level of serum ionized calcium. To do this, it acts on the gut, kidney, and bones. In the gut, it increases the absorption of dietary calcium. In the kidneys, phosphate resorption is decreased, causing elevation of the calcium level.
Parathormone causes resorption of calcium from the bones, which act as a giant calcium warehouse.
Therefore, the main finding in the bones with hyperparathyroidism is osteopenia of various types. This may present as a diffuse global osteopenia, or one may see more focal evidence of bone resorption. Some of this resorption occurs in nonspecific patterns, such as intracortical tunneling, endosteal resorption, or trabecular resorption, which can all be seen in many other causes of osteopenia. However, hyperparathyroidism can also present with more specific patterns of osteopenia, such as that seen in the skull above, or in the fingers below in the same patient. Such subperiosteal resorption is virtually pathognomonic for hyperparathyroidism, and usually more common along the radial margin of the fingers, for reasons which are obscure.