The most common cause of decreased menstrual flow in women in their 40s is ovarian hypoplasia, which leads to decreased menstrual flow, often accompanied by decreased libido, menstrual cycle disorders, etc. A blood test for sex hormone hexa-test can be taken on the 2nd-3rd day of menstruation to find out if the ovaries are functioning normally, and to find out if estradiol is decreasing. It is also possible to see if the decrease in menstrual flow is due to elevated prolactin, or if the decrease is due to elevated androgens. A comprehensive evaluation is needed to determine if intervention is needed. An ultrasound is also recommended to rule out the presence of pelvic tumors or thinning of the endometrium before treatment is given.