Which of the following is considered a potentially life-threatening side effect associated with hormone replacement therapy?

Breast tenderness is a common and generally mild side effect of hormone replacement therapy, often resulting from hormonal changes in the body. While it may cause discomfort, it is not classified as a life-threatening condition and typically resolves with continued use of HRT or dosage adjustments.

Headaches may occur as a side effect of hormone replacement therapy, usually related to fluctuations in hormone levels. While they can be bothersome and affect quality of life, headaches are not considered potentially life-threatening and can often be managed effectively with medication or lifestyle changes.

Vaginal bleeding can be a side effect of hormone replacement therapy, particularly during the initial phases of treatment or with specific formulations. Although it may require medical evaluation to rule out other causes, it is not categorized as a life-threatening side effect compared to thromboembolism.