Estrogen

Estrogen plays a critical role in regulating bone metabolism in men.  As in women, estrogen is a key sex steroid regulating bone metabolism in men.  Those lacking only estrogen experience significant increases in markers of bone resorption.  Treatment with testosterone, estrogen or both maintained osteocalcin levels.  Both appear to play a major role in maintaining bone formation, inhibiting osteoblast apoptosis (regulated cell death).

Kholsa, S. Cold Spring Harb Perspect Med 2018;8:a031211.