What results from high levels of parathyroid hormone (PTH)?

High levels of parathyroid hormone (PTH) primarily lead to renal osteodystrophy, which is a bone disorder associated with chronic kidney disease. When the kidneys fail to excrete phosphate effectively, it can lead to hyperphosphatemia. This condition, combined with low levels of active vitamin D (due to impaired kidney function), causes a decrease in serum calcium levels. In response to low calcium, the parathyroid glands secrete more PTH to try to mobilize calcium from bones, leading to changes in bone metabolism.

Renal osteodystrophy is characterized by alterations in bone morphology and function due to the combined effects of elevated PTH levels, imbalanced calcium and phosphate metabolism, and vitamin D deficiency. The outcome is often reduced bone density and resilience, leading to increased fractures and bone pain.

While hypercalcemia, osteoporosis, and hypocalcemia can occur in various contexts related to calcium metabolism and bone health, they do not directly result from the elevated PTH associated with renal disease. Renal osteodystrophy specifically reflects the consequences of disturbed mineral metabolism in the context of chronic kidney disease, making it the correct answer.