Background: Osteoporosis could be associated with the hormone therapy for metastatic prostate carcinoma (PCa) and with PCa per se. The objective of this review is to determine the incidence of bone loss and osteoporosis in patients with PCa who are or are not treated with hormone therapy (ADT). Methods: The Medline, Embase, Cancerlit, and American Society of Clinical Oncology Abstract databases were searched for published studies on prostate cancer and bone metabolism. The outcomes assessed were: fracture, osteoporosis and osteopenia. Results: Thirty-two articles (116,911 participants) were included in the meta-analysis. PCa patients under ADT had a higher risk of osteoporosis (RR, 1.30; p < 0.00001) and a higher risk of fractures (RR, 1.17; p < 0.00001) as compared to patients not under ADT. The total bone mineral density was lower in patients under ADT when compared with patients not under ADT (p = 0.031) but it was similar to bone mineral density found in healthy controls (p = 0.895). The time of androgen deprivation therapy correlated negatively with lumbar spine and total hip bone mineral density (Spearman's rho = -0.490 and -0.773; p = 0.028 and 0.001, respectively) and with total hip t score (Spearman's rho = -0.900; p = 0.037). Conclusion: We found consistent evidence that the use of androgen deprivation therapy in patients with PCa reduces bone mineral density, increasing the risk of fractures in these patients.