The second day of the menstrual period mainly refers to the follicular phase. After entering the menstrual cycle, from the first day to the third day, the follicles will secrete a large amount of estrogen, which can better reflect the level of follicle-stimulating hormone, and can further diagnose whether a woman has endocrine disorders, and sex hormone examination on the second day of menstruation is often the most accurate. Through a series of data examination, we can understand whether the ovarian function is normal or not, ovarian function decline is very easy to have estrogen secretion abnormality, which will affect women’s ability to conceive, it is very important for women’s physiological testing.