Grant: Operating Grant

During pregnancy and lactation (breast-feeding), a woman will lose calcium from her body in order to provide it to the developing fetus and suckling neonate, respectively. During pregnancy, a woman meets this calcium demand by doubling intestinal absorption of calcium and by losing some calcium from her skeleton. During six months of lactation, a woman meets the neonate's demand for calcium by losing 5 to 10% of the calcium content of her skeleton. The rate of loss of skeletal calcium during lactation is extremely fast when it is considered that a loss of more than 1% per year is termed "rapid" in a woman at menopause. After weaning the baby, calcium that was lost from the skeleton during pregnancy and lactation is completely restored at rates that far exceed what current treatments for osteoporosis can accomplish. The recovery is especially remarkable when it is considered that, apart from pregnancy and lactation, losses of calcium from the adult skeleton are at best only slowly and incompletely restored (eg from estrogen deficiency, illness, weightlessness, etc). In this work we are trying to understand how the skeleton recovers lost calcium so quickly and readily after lactation because this knowledge might lead to new ways to restore calcium to the skeleton in people with osteoporosis or other conditions of low bone mass. This work involves mice, which lose up to 55% of skeletal calcium during 3 weeks of lactation, and fully restore the skeleton within 10-14 days after weaning.