Treatment of conditions that present with low bone mass by continuous combination therapy with selective prostaglandin ep4 receptor agonists and an estrogen

This invention is directed to methods for treating conditions which present with low bone mass in a patient in need thereof using continuous combination therapy with a synergistically effective combination of an EP4 receptor selective agonist or a pharmaceutically acceptable salt thereof, such as 5-(3-{2S-[3R-hydroxy-4-(3-trifluoromethyl-phenyl)-butyl]-5-oxo-pyrrolidin-1-yl}-propyl)-thiophene-2-carboxylic acid or a pharmaceutically acceptable salt thereof; and an estrogen or a pharmaceutically effective salt thereof, The present methods are useful for treating conditions that present with low bone mass including osteoporosis, osteotomy, osteoporotic fracture, childhood idiopathic bone loss, periodontitis and low bone mass and for enhancing bone healing following facial reconstruction, maxillary reconstruction or mandibular reconstruction, inducing vertebral synostosis, enhancing long bone extension, enhancing the healing rate of a bone graft or a long bone fracture or enhancing prosthetic ingrowth in a patient in need thereof.