Women's trouble: Every little bit hurts: Dysmenorrhoea & premenstrual syndrome

Doppler flow studies suggest that dysmenorrhoea (primary and secondary) is caused by frequent and prolonged uterine contractions that decrease blood flow to the myometrium, resulting in ischemia. The sequential stimulation of the endometrium by oestrogen (in the follicular phase) followed by progesterone (in the luteal phase) results in a large increase in endometrial stores of arachidonic acid, a precursor to prostaglandin production.