Pregnancy-associated osteoporosis with elevated levels of circulating parathyroid hormone-related protein: a report of two cases.

Two lactating women who had complained of back pain developed spontaneous vertebral fractures with low bone mineral density (BMD) several months postpartum. The back pain and biochemical abnormalities presented as hypercalcemia and elevated plasma levels of the parathyroid hormone-related protein (PTH-rP) that returned to normal indices with increasing BMD after weaning. The increased circulating PTH-rP might contribute to the pregnancy-associated osteoporosis in women who probably are already osteopenic.