The present invention relates to conformationally constrained parathyroid hormone (PTH) analogs and derivatives of those analogs. The invention also provides methods of preparing and using the PTH analogs. Further, the invention encompasses compositions and methods for use in limiting undesired bone loss in a vertebrate at risk of such bone loss, in treating conditions that are characterized by undesired bone loss or by the need for bone growth, e.g. in treating fractures or cartilage disorders and for raising camp levels in cells where deemed necessary.