What is the effect of parathyroid hormone on osteoclast activity?

• A. It decreases osteoclast activity
• B. It increases osteoclast activity
• C. It has no effect on osteoclast activity
• D. It inhibits osteoclast activity

Answer: (B)

Parathyroid hormone (PTH) plays a crucial role in calcium homeostasis within the body. One of its primary effects is to increase osteoclast activity. Osteoclasts are specialized cells responsible for bone resorption, meaning they break down bone tissue and release calcium into the bloodstream.

When parathyroid hormone is released from the parathyroid glands in response to low blood calcium levels, it stimulates osteoclasts to become more active. This process leads to an increase in the breakdown of bone, thereby raising the levels of calcium in the blood. In addition to stimulating osteoclasts directly, PTH also influences the production of other molecules, like RANKL (Receptor Activator of Nuclear factor Kappa-Β Ligand), which further promotes the maturation and activity of osteoclasts.

Understanding this effect is essential for comprehending the body's mechanisms for regulating calcium levels and the interplay between bone formation and resorption. This is especially important in conditions such as osteoporosis, where there is an imbalance in bone remodeling.