Directly, it acts via insulin and insulin-like growth factor-1 (IGF-1) receptors on osteoblasts, while indirectly, it regulates blood glucose levels and modulates the activity of parathyroid hormone, IGF-1, and vitamin D. Disruptions in insulin signaling can negatively impact bone health, increasing the risk of osteoporosis and fractures. Here, PTH is linked to osteoporosis.