UWorld Endocrine Practice Test

Parathyroid hormone (PTH) plays a crucial role in regulating calcium homeostasis in the body, particularly in relation to bone health. Its primary action on bone tissue is to stimulate bone resorption. This process involves the activation of osteoclasts, the cells responsible for breaking down bone tissue. As osteoclast activity increases, minerals such as calcium and phosphate are released into the bloodstream.

This increase in bone resorption serves to elevate the levels of calcium in the blood, which is vital for numerous physiological functions, including muscle contraction, nerve impulse transmission, and blood clotting. Therefore, the effect of PTH on bone tissue is characterized by its capacity to mobilize calcium from the bones into circulation, effectively increasing calcium levels in the bloodstream when needed.

The other options do not accurately represent PTH’s specific actions on bone. While PTH does influence calcium absorption indirectly through its effects on the kidneys and intestines, its direct effect on bone is primarily through resorption and releasing calcium, making the chosen answer the most accurate reflection of PTH’s role within the context of bone tissue.