Ovulation is the main task of the ovaries and a reliable guarantee of a normal menstrual cycle, therefore, ovulation is directly related to the menstrual cycle. The normal function of ovaries can be affected and cause ovulation disorders. 2, endocrine disorders: hypothalamus, pituitary gland dysplasia, dysfunction and tumors can affect the function of the ovaries, and high prolactin in the blood can make the ovarian tissue unresponsive to sex hormones, so that ovulation does not occur. 3, various diseases of the ovaries themselves: such as ovarian dysplasia, radioactive surgery or inflammation that destroys ovarian tissue, or tumors in the ovaries can make the ovaries unable to cope with normal ovulation and hormone secretion functions. Therefore, it is important to identify the cause if the basal body temperature is monophasic for a long time.