Kyphosis. Computer illustration of the development of kyphosis (spinal curvature) in a woman as she ages. Kyphosis is due to a disorder of the vertebrae. It is usually caused by osteoporosis (bone thinning), although a fractured vertebra or a vertebral tumour may have the same effect. Osteoporosis is most common in woman after the menopause as their ovaries stop producing the oes- trogen hormones that help to maintain bone mass.