Absence of menstruation is divided into two as primary and secondary. Primary amenorrhea is the absence of menstruation, and secondary amenorrhea is the absence of menstruation for 6 months in a woman who had menstruation before, it is physiological in pregnancy, breastfeeding and menopause.
The most common cause of primary amenorrhea is a condition called hypergonadotropic hypogonadism, where the eggs are not functioning properly. Outflow tract anomalies in the genital system (where the hymen covers the vaginal entrance), hyperprolactinemia (high prolactin), thyroid hormone dysfunction, androgen insensitivity, enzyme deficiencies are also causes of primary amenorrhea.
The most common cause of secondary ammonia is pregnancy. Other causes include intrauterine adhesions (Asherman syndrome), high prolactin, thyroid hormone dysfunction, decreased ovarian reserve, polycystic ovary syndrome, and menopause.