The estrogen deficiency that occurs at menopause leads to an imbalance in the RANKL-osteoprotegerin system, inducing osteoclastogenesis and accelerated bone resorption.[16] It also causes an upregulation of cytokines such as interleukin-6 produced in bone marrow stromal cells, which increase bone turnover.[15] During the rapid phase of bone loss, removal of calcium from bone increases plasma calcium levels, which suppresses the secretion of PTH. The PTH then causes calciuria, suppression of renal calcitriol production, and reduction of intestinal calcium absorption.