- Modulation of osteogenic cell ultrastructure by RS-23581, an analog of human parathyroid hormone (PTH)-related peptide-(1-34), and bovine PTH-(1-34). Leaffer, D., Sweeney, M., Kellerman, L.A., Avnur, Z., Krstenansky, J.L., Vickery, B.H., Caulfield, J.P. Endocrinology (1995)