Osteoporosis has become one of the most widely recognized disorders of our times affecting an estimated 25 million women in this country. Recent evidence has suggested that premenstrual syndrome (PMS) is associated with a calcium deficiency state and bone loss. This may place premenopausal women at greater risk for osteoporosis. An entity such as PMS may be an important physiological marker of a calcium disturbance. The purpose of this investigation is to understand more completely the extent to which calcium balance is disturbed in severe PMS or Premenstrual Dysphoric Disorder (PMDD) by utilizing new tools to assess calcium and bone turnover. The long term objective is to elucidate the pathophysiology of PMDD or severe PMS as it relates to calcium hormones and bone markers. The experimental design involves the comparison between women witn severe PMS and asymptomatic controls.