Thoracic aortic aneurysms most often result from cystic medial degeneration. Cystic medial degeneration occurs normally to some extent with aging, but the process is accelerated by hypertension and atherosclerosis. Risk factors for cystic medial degeneration include Marfan syndrome, Ehlers-Danlos syndrome, or Turner syndrome; familial thoracic aortic aneurysm syndrome; bicuspid aortic valve; infection (e.g., syphilis) and/or inflammation (e.g., Takayasu's and giant cell arteritis).
Abdominal aortic aneurysms are much more common than thoracic aortic aneurysms. Smoking is the risk factor most strongly associated with abdominal aortic aneurysms, followed by age, hypertension, hyperlipidemia, and atherosclerosis. Sex and genetics also influence aneurysm formation. Men are 10x more likely than women to have an abdominal aortic aneurysm of 4 cm or greater. Those with a family history of abdominal aortic aneurysm have an increased risk of 30%, and their aneurysms tend to occur at a younger age and carry a greater risk of rupture than do sporadic aneurysms.
The field of view of CT cardiac for calcium scoring can vary from institution to institution but is typically coned down to focus on the heart. This incidentally includes portions of the ascending and descending thoracic aorta and may include portions of the suprarenal abdominal aorta but does not include the infrarenal abdominal aorta where abdominal aortic aneurysms (AAA) commonly occur. If your doctor wants to screen for AAA, consider US Doppler, CTA, and/or MRA.