American Board of Orthodontics (ABO) Practice Exam

Parathyroid hormone (PTH) primarily affects bone tissue by stimulating bone resorption. This process involves the activation of osteoclasts, the cells responsible for breaking down bone material. When PTH is secreted in response to low blood calcium levels, it targets the bones, leading to the release of calcium into the bloodstream by promoting the resorption of bone tissue.

Bone resorption is crucial because it helps maintain calcium homeostasis in the body. By increasing the activity of osteoclasts, PTH indirectly supports the availability of calcium for various physiological functions, including muscle contraction and nerve impulse transmission. This mechanism is essential for maintaining normal serum calcium levels, especially when dietary intake may not be sufficient.

In contrast, options related to stimulating bone formation, inhibiting calcium absorption, or enhancing collagen synthesis do not accurately reflect the primary role of PTH in bone tissue response. While other hormones and factors can influence bone formation and collagen synthesis, PTH's primary impact is clearly more aligned with bone resorption.