In the American Journal of Obstetrics and Gynecology Dr. JoAnn Pinkerton of the University of Virgina and co-workers wrote an article about what conditions are worsened by having one's menstrual period. Some were obvious: a pimple, PMS, and migraines, and some were suspected by not really discussed much with your physician: irritable bowel, diabetes, asthma, and rashes (uticaria and itching)! What was surprising to read was the good research that even conditions like acute appendicitis, and seizures, and glaucoma, and MS and Rheumatoid arthritis can be made worse during one's period. Other studies have linked ligament weakness! The immune system seems to be very hormone dependent, and which immune cells are both produced and functioning depends upon the phase of the menstrual cycle you are in. Hormones are also strong controlling factors over brain chemistry and bipolar disorders and anxiety related disorders like agoraphobia may become worse in the premenstrual time of the cycle. Even an overt eating disorder like bulimia may be made worse by the premenstrual phase. With the psychological conditions, knowing if these conditions are just PMDD or an exacerbation of the pre-existing condition is what is important for a gyno to sort. In women in their 40s or who are perimenopausal, cycle fluctuations can make this even more difficult to determine, as simple blood testing cannot really tell. Tracking of cycle days relative to the symptoms may be the best way to go about determining the link.