Why subperiosteal resorption happens on radial side in hyperparathyroidism?

why subperiosteal resorption happens on radial side in hyperparathyroidism?

Subperiosteal resorption refers to the process of bone resorption or loss of bone tissue occurring just beneath the periosteum, the thin membrane that covers the outer surface of bones. In the context of hyperparathyroidism, specifically primary hyperparathyroidism, subperiosteal resorption can occur, and it often affects the radial (forearm) side of the bone. Here’s why this occurs:

  1. Hyperparathyroidism and Elevated Parathyroid Hormone (PTH):
  • Hyperparathyroidism is a condition characterized by the overproduction of parathyroid hormone (PTH) by one or more of the parathyroid glands located in the neck.
  • PTH plays a crucial role in regulating calcium and phosphate levels in the body. Excess PTH in hyperparathyroidism leads to increased calcium levels in the blood (hypercalcemia).
  1. Bone Resorption:
  • Elevated levels of PTH stimulate the activity of osteoclasts, which are specialized cells responsible for breaking down bone tissue (bone resorption). Osteoclasts are activated to release calcium into the bloodstream, primarily from the skeleton.
  1. Subperiosteal Resorption:
  • In hyperparathyroidism, the overactive osteoclasts can target the bone tissue just beneath the periosteum, resulting in subperiosteal resorption.
  • The radial (forearm) side of the bone is particularly susceptible to this resorption because it contains a thin layer of cortical bone just beneath the periosteum. This cortical bone is more vulnerable to osteoclastic activity compared to the trabecular bone deeper within the bone shaft.
  1. Clinical Manifestations:
  • Subperiosteal resorption can lead to bone pain, tenderness, and weakness, particularly in the forearm bones. Patients with hyperparathyroidism may experience symptoms such as “brown tumors” (areas of bone resorption) and bone deformities.
  1. Radiological Findings:
  • On X-rays, subperiosteal resorption may appear as a characteristic “subperiosteal resorption line” along the radial aspect of the bones. This radiological finding is indicative of hyperparathyroidism-related bone changes.

In summary, subperiosteal resorption on the radial side of bones is a result of the increased osteoclastic activity driven by elevated PTH levels in hyperparathyroidism. The specific vulnerability of the radial bone cortex to this resorption is due to its proximity to the periosteum. It is one of the skeletal manifestations of primary hyperparathyroidism and is typically seen in association with hypercalcemia. Treatment of primary hyperparathyroidism often involves addressing the underlying parathyroid gland dysfunction and managing calcium levels to prevent further bone damage.