What is an absolute contraindication to post-menopausal hormone therapy?

Unexplained vaginal bleeding serves as an absolute contraindication to post-menopausal hormone therapy because it may indicate a more serious underlying condition, such as endometrial cancer or other abnormalities of the reproductive system. Hormone therapy can potentially exacerbate these conditions by stimulating the endometrial lining, which may lead to increased risks for the patient. Thus, it is crucial to thoroughly evaluate the cause of unexplained bleeding before considering hormone therapy.

The other conditions listed do not present the same level of risk when it comes to initiating hormone therapy. For instance, while cigarette smoking, seizure disorders, and endometriosis may require careful consideration or closer monitoring during treatment, they do not automatically preclude the use of hormone therapy as a whole. Therefore, unexplained vaginal bleeding stands out distinctly as a critical reason to avoid starting hormone therapy until a full evaluation has been conducted.