In a patient experiencing symptoms indicative of menopause, which diagnostic test is likely most useful to confirm the diagnosis?

In the context of diagnosing menopause, measuring Follicle Stimulating Hormone (FSH) levels is the most useful diagnostic test. During menopause, the ovaries produce less estrogen, which leads to an increase in FSH levels due to reduced negative feedback on the pituitary gland. An elevated FSH level, typically greater than 30 mIU/mL, is indicative of menopause and reflects the transition of the body from reproductive to non-reproductive status.

Assessing FSH levels is particularly relevant because menopause is primarily defined by the cessation of ovarian function and the consequent hormonal changes. While other diagnostic tools may evaluate various health conditions, FSH provides a direct insight into the ovarian reserve and confirms the menopausal status effectively.