Which of the following explains the thickening of bone seen in osteitis deformans?

The thickening of bone observed in osteitis deformans, also known as Paget's disease of bone, is primarily due to increased bone turnover and abnormal bone architecture. This condition is characterized by an increase in osteoclastic bone resorption followed by an increase in osteoblastic new bone formation. However, the newly formed bone is often disorganized and structurally abnormal, leading to the characteristic thickening and enlargement of the bones affected.

During the disease process, the normal regulation of bone remodeling is disrupted. As bone resorption increases, osteoblasts attempt to compensate by forming new bone. However, since this new bone is laid down in a haphazard manner, the overall quality of the bone is compromised, resulting in a thickened but structurally weak bone. This abnormal bone remodeling process is what ultimately leads to the typical clinical manifestations associated with Paget's disease, including deformities, pain, and an increased risk of fractures.

In summary, the answer is correct as it encapsulates both the increased activity of bone remodeling involved in the disease and highlights the resultant abnormal architecture, which is central to understanding the characteristics of osteitis deformans.