Which two factors' decrease may hinder older individuals from forming bone rapidly?

• A. Hormones and minerals
• B. Growth factor and IGF-1
• C. Calcium and vitamin D
• D. Thyroid hormones and estrogen

Answer: (B)

The correct answer focuses on the interplay between growth factors and insulin-like growth factor 1 (IGF-1) in bone health. As individuals age, there is a natural decline in the levels of various growth factors and hormones that play a critical role in bone formation and remodeling.

IGF-1, which is primarily produced in the liver and influenced by growth hormone, is crucial for bone density and development. It promotes the proliferation and differentiation of osteoblasts, the cells responsible for building bone. A reduction in IGF-1 can lead to decreased osteoblast activity, thereby hindering the formation of new bone tissue in older individuals.

Additionally, while other factors like hormones and minerals, or vitamin levels are important for overall skeletal health, the specific decline in growth factors and IGF-1 directly affects the cellular processes needed for rapid bone formation. Thus, understanding the role of IGF-1 and related growth factors provides insight into the challenges faced by older adults in maintaining bone density.