Final answer:
Postmenopausal women experience increased bone fragility and fractures due to decreased estrogen production, which leads to diminished osteoblastic activity, increased bone brittleness, and the development of osteoporosis.
Step-by-step explanation:
Postmenopausal women are more prone to fractures primarily because their bones become weaker due to decreased estrogen levels. Estrogen is vital in promoting osteoblastic activity and bone matrix production, which are essential for maintaining strong bones. When women go through menopause, typically around the age of 50, their ovaries reduce in size and cease the production of estrogen, leading to a decrease in bone density and an increase in bone brittleness, which makes fractures more likely. Additionally, this drop in estrogen contributes to the development of osteoporosis, a condition characterized by the weakening of bones and an increased risk of fractures.