PMS: hints of a link to lunchtime and zinc.

PMS: Hints of a link to lunchtime and zinc

Many women suffer from crying jags, eating binges, anxiety, bloating and other premenstrual symptoms that can disrupt some aspect of their professional and personal lives for a few days each month. At one time, physicians widely considered such symptoms psychosomatic, but accumulating evidence now points toward out-of-kilter hormone levels as the cause. Last week, endocrinologists from Texas reported the first data suggesting that zinc may play a role in premenstrual syndrome (PMS), and a group from Kentucky described an after-lunch progesterone plunge that might help explain some PMS symptoms.

Some researchers suspect that a deficiency of progesterone underlies PMS. The ovaries secrete this sex hormone during the menstrual cycle's luteal phase -- the 13 days preceding menstruation, when PMS symptoms typically erupt. Because trace amounts of zinc regulate the secretion of certain hormones, including progesterone, scientists at the Baylor College of Medicine in Houston decided to look for zinc abnormalities in the blood of women with PMS.

C. James Chuong and his co-workers recruited 10 women with PMS and 10 controls who reported no sign of the monthly disorder. They collected blood samples from the volunteers every two to three days during three menstrual cycles and measured zinc concentrations in the clear serum component of the blood. During the luteal phase, the investigators discovered significantly lower zinc levels in blood from women with PMS than in the control samples. Chuong reported the team's results at the 46th annual meeting of the American Fertility Society in Washington, D.C.

A zinc deficiency might lead to a decrease in secretions of progesterone and certain natural opiates, or endorphins, produced by neurons in the brain, Chuong speculates. In an earlier study, he found that women with PMS have lower blood levels of endorphins during the luteal phase than do women without PMS. The interplay among zinc, progesterone and these morphine-like natural pain-killers remains unclear, he adds.

Chuong warns PMS sufferers against popping pills to supply the trace metal -- which can be toxic in large doses -- until scientists demonstrate a dietary zinc deficiency in women with the monthly disorder. And even if zinc deficiency plays a contributing role, it might affect only a subgroup of PMS patients, he notes.

Another study presented at last week's meeting suggests that an afternoon drop in blood progesterone levels may somehow contribute to PMS symptoms, especially the cravings for sweet or salty foods, which can lead to the eating binges reported by some women with PMS.

Despite widespread suspicion that hormone problems cause PMS, recent attempts to demonstrate a measurable difference in blood concentrations of the sex hormones have yielded little if any support for that theory, notes Ken N. Muse, a reproductive endocrinologist at the University of Kentucky in Lexington. However, Muse speculates that such studies may have missed transient drops in progesterone by relying on once-a-day blood sampling. He and his colleagues decided to take a different tack, using blood samples drawn at 30-minute intervals from 11 women in the luteal phase.

Those samples revealed that all six volunteers with PMS experienced a steep progesterone drop in the first few hours after lunch, he reports. Healthy women typically show a decline in blood progesterone after eating the midday meal, he says, but the volunteers with PMS showed an exaggerated hormonal response to their repast.

Whether that response leads to eating binges or other PMS symptoms remains unknown, notes PMS researcher Robert L. Reid of Queen's University in Kingston, Ontario. "Further work needs to be done," he says, to draw such a connection and to confirm the proposed link between PMS and zinc.