PRL and hyperprolactinemia: Moshtaghi-Kashanian et al. in 2006 showed an increased level of prolactin in concurrent opium and cigarette smokers in comparison with cigarette smokers alone (86.96% vs. 41.65%).[15] Other researches also reached the same results.[16][22][23] Hyperprolactinemia is one of the well known risk factors for developing bone loss that is another explanation for increased risk of bone loss and bone fracture in opium addicted persons.