ATI Pathophysiology Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Parathyroid hormone (PTH) plays a crucial role in maintaining calcium homeostasis in the body, and its effects are observed in multiple systems, including bones, kidneys, and intestines.

In the bones, PTH stimulates the activity of osteoclasts, which are cells responsible for breaking down bone tissue. This process releases calcium into the bloodstream, increasing serum calcium levels.

In the kidneys, PTH promotes the reabsorption of calcium from urine, reducing calcium loss and thus contributing to overall calcium retention in the body. PTH also stimulates the conversion of vitamin D into its active form, calcitriol, which enhances intestinal absorption of calcium.

In the intestines, the active form of vitamin D, stimulated by PTH, increases the absorption of calcium and phosphate from dietary sources.

Thus, PTH's effects are indeed systemic, involving the bones, kidneys, and intestines, highlighting its essential role in regulating calcium levels in the body. This comprehensive action across multiple sites underscores why it is accurate to say that parathyroid hormone exerts its effects in all of these areas.