In part, but not entirely. Bone mass declines in proportion to the number of menstrual cycles missed and low estrogen levels increase the rate of bone resorption. However, low energy availability also suppresses anabolic hormones (e.g. thyroid hormone, insulin and insulin-like growth factor-1) that stimulate bone formation. This is especially hazardous in adolescence, when a faster rate of formation than resorption is needed for skeletal development.