Menstruation is essential for human reproduction. But many women find the monthly cycle a bit of a nuisance. This may be due to premenstrual symptoms, heavy bleeding or simply the inconvenience of it. But some women are unfortunate in that they experience all the premenstrual discomfort amplified ten-fold.
Hormones and the menstrual cycle
Complex cellular mechanisms keep everything in check. These hormones - acting on multiple sites all over the body and not specifically on the reproductive organs - are the reason for all the troubling symptoms.
The serum concentrations of these hormones and other potent chemicals are usually very small. They act both locally and systemically. The production, action and removal of these hormones is tightly regulated. Any mishap in these complex regulatory pathways results in excessive secretion, inadequate secretion or improper function of these hormones.
Among the potent chemicals involved in the regulation of menstruation, prostaglandins are one of the most important. Its synthesis is simple enough, but there is an enormous range of prostaglandin types. These act on different tissues, giving different effects.
Phospholipids get transformed into arachidonic acid. The cyclooxygenase pathway converts arachidonic acid to prostaglandin and prostacyclin.
Prostaglandins act locally just before menstruation to peel the endometrial lining off the inner uterine wall. Prostaglandin contracts smooth muscle of blood vessels of the uterus, causing a gradual ischemia.
Systemically prostaglandins act at multiple sites, including the hypothalamus which contains the temperature control center of the body. The temperature control center contains an anterior heat-reducing component and a posterior heat-promoting component.
Under the stimulation of prostaglandin, the heat-promoting center neurons increase their firing rate. Chemical stimulation of these heat-promoting areas results in the production of more heat. With more heat production, the core body temperature rises.
When the environmental temperature is lower than the body temperature, a lot of heat is lost through conduction and convection. This rapid heat loss is felt as freezing, in the same way you would feel an intense cold when you touch a piece of iron in a cold climate because the heat is conducted in to the piece of iron.
Prostaglandins secreted locally can stimulate pain-sensitive neurons. It also lowers the pain threshold in the brain. In women with systemic prostaglandin production during menstruation, generalized joint pains and body aches are very common.
Another effect of prostaglandins is the reduction of bowel motility. The intestinal transit time of food becomes longer. Forward directed rhythmic contractions of the bowels slow down. This may present as nausea, vomiting and constipation.
It is important to understand that premenstrual syndrome is caused by the same chemicals that control the cycles. But if premenstrual syndrome is unbearable, some medical intervention may be warranted. The principle is to inhibit the synthesis of prostaglandin and other harmful chemicals systemically. Cyclooxygenase inhibitors and non-steroid anti-inflammatory drugs reduce the prostaglandin formation and provide a certain amount of relief.
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