What is the outcome of high levels of parathyroid hormone (PTH)?

• A. Decreased calcium absorption
• B. Increased calcium release from bones
• C. Increased insulin resistance
• D. Decreased metabolism

Answer: (B)

High levels of parathyroid hormone (PTH) primarily stimulate increased calcium release from bones. PTH is crucial in regulating calcium levels in the blood, and when its concentration is elevated, it signals bones to release calcium into the bloodstream. This process occurs through the action of osteoclasts, which break down bone tissue and release stored calcium.

Understanding the role of PTH in calcium regulation is essential, as the hormone also increases calcium reabsorption in the kidneys and enhances intestinal absorption of calcium indirectly through vitamin D activation. This interplay maintains calcium homeostasis, elevating blood calcium levels when necessary. Thus, the correct answer highlights the direct effect of high PTH levels on bone tissue, showcasing its significance in calcium metabolism.