What is the primary effect of primary hyperparathyroidism (PHPT) on bone density?

In primary hyperparathyroidism (PHPT), there is an excessive production of parathyroid hormone (PTH), which plays a central role in calcium homeostasis. One of the significant effects of elevated PTH levels is an increase in bone turnover. In PHPT, this occurs because PTH stimulates osteoclast activity, which leads to increased bone resorption.

While bone turnover can be observed in various skeletal sites, the forearm is a notable area where increased turnover can lead to extensive bone loss, sometimes resulting in osteoporosis. The increase in osteoclastic activity ultimately causes a decrease in the mineral density of the bone, particularly in regions that are more metabolically active.

Contrary to other statements, the condition does not result in decreased bone turnover; instead, it is characterized by an imbalance where resorption outpaces formation, which leads to a net loss of bone density. Thus, the correct answer highlights the impact on bone turnover within the forearm, emphasizing the changes that occur due to the overactivity of the parathyroid hormone in this specific skeletal region.