Final answer:
The most likely diagnosis for the abnormally increased curvature of the thoracic vertebral column is kyphosis. Kyphosis is an excessive posterior curvature of the thoracic region and can develop due to osteoporosis causing the collapse of vertebrae.
Step-by-step explanation:
The most likely diagnosis for a 70-year-old man with an abnormally increased curvature of the thoracic vertebral column is kyphosis. Kyphosis is an excessive posterior curvature of the thoracic region and can develop when osteoporosis causes weakening and erosion of the anterior portions of the upper thoracic vertebrae, resulting in their gradual collapse. This condition is also referred to as humpback or hunchback.