Novel parathyroid hormone (PTH) polypeptide derivatives are disclosed, as are pharmaceutical compositions containing said polypeptides, and synthetic and recombinant methods for producing said polypeptides. Also disclosed are methods for treating mammalian conditions characterized by decreases in bone mass using therapeutically effective pharmaceutical compositions containing said polypeptides. Also disclosed are methods for screening candidate compounds of the invention for antagonistic or agonistic effects on parathyroid hormone receptor action. Also disclosed are diagnostic and therapeutic methods of said compounds.