Final answer:
The disease being described is osteoporosis, which causes the gradual loss of bone density and strength. It can lead to a collapse of the thoracic vertebrae and excessive curvature of the thoracic region.
Step-by-step explanation:
Based on the provided information, the disease being described is osteoporosis. Osteoporosis is an age-related disorder that causes the gradual loss of bone density and strength. When the thoracic vertebrae are affected, there can be a gradual collapse of the vertebrae, resulting in kyphosis, an excessive curvature of the thoracic region.