The Cause of Period Pain

Menstrual cramps are triggered by prostaglandins, produced in the uterus. Unlike other hormones, prostaglandins are site specific and can be produced in nearly all the organs. Period pain is triggered specifically by uterine PGE2. This modulates inflammation and is involved in muscle contractions, blood vessel constriction, blood clotting, and pain.

Shortly before a period begins, the endometrial cells that form the lining of the uterus make large amounts of PGE2. When these cells break down during menstruation, the prostaglandins are released. They constrict the blood vessels in the uterus and make its muscle layer contract, causing painful cramps. Some of the prostaglandins also enter the bloodstream, causing headache, nausea, vomiting, and diarrhea.

Researchers have measured the number of prostaglandins produced by the endometrial cells and found that it is higher in women with menstrual pain than in women who have little or no pain.

NSAIDs have demonstrated some success in mitigating period pain by inhibiting enzymes known as COX-1 and COX-2 that produce PGE2. The prostaglandins made by COX-1 and COX-2 are those responsible for the formation of blood platelets, pain and inflammation.

However, according to a 2010 study published in the British Medical Journal, naproxen sodium and other NSAIDs increased the risk of stroke and myocardial infarction. The study also reviewed previous research that suggested there is a link between fatal and non-fatal cardiovascular disease and NSAIDs.

Prostaglandins are lipid autacoids derived from arachidonic acid. They both sustain homeostatic functions and mediate pathogenic mechanisms, including the inflammatory response.

Note - not all PG’s contribute to pain. Prostaglandins are pivotal in both "the promotion and resolution of inflammation." While some, such as PGE2, modulate pain and inflammation, other types of PG’s serve to minimize pain and inflammation.

Prostaglandins are known to regulate the female reproductive system generally. They are involved in the control of ovulation, the menstrual cycle and the induction of labour. Indeed, manufactured forms of prostaglandins - prostaglandin E2 and F2 can be used to induce labour.