Which hormone is primarily measured to assess for perimenopause?

The primary hormone measured to assess for perimenopause is follicle-stimulating hormone (FSH). During the perimenopausal phase, ovarian function begins to decline, leading to changes in hormone production. As the ovaries produce fewer eggs, there is a decrease in estrogen levels and an increase in FSH levels. This elevation in FSH is the body's response to insufficient estrogen, as FSH is responsible for stimulating the growth and maturation of ovarian follicles. Monitoring FSH levels can provide insight into the status of ovarian function, helping to determine whether a woman is in perimenopause.

Other hormones can provide additional information about the reproductive status, but FSH is the most utilized hormone for assessing perimenopause because of its direct relationship with the changes occurring in the ovaries during this transitional phase.