Raloxifen belongs to the class of compounds known as SERMs or selective estrogen receptor modulators. SERMs decrease activity of estrogen and are therefore considered an “anti-estrogen” treatment. However, SERMs do not act by decreasing serum estrogen or aromatase-mediated conversion, but rather through a blocking activity at the estrogen receptor on a cellular level. In other words, raloxifen and its metabolites are active at the estrogen receptor but not as an estrogen-like stimulus (agonist). Instead, they prevent estrogen from exerting its effects at the cellular level. This (as well as other means of blocking estrogenic activity or reducing estrogen levels) creates a rise in testosterone in men because testosterone production is modulated partially via serum estrogen levels.
Raloxifen and its sister drug tamoxifen are typically used in treating estrogen-receptor dependent breast cancer in women. Raloxifen may prove to have more diverse uses than tamoxifen for several reasons:
Selective estrogen receptor modulators (SERMs) or estrogen agonists/antagonists have shown promise in osteoporosis in that they have the potential to reduce the risk of fracture, and also reduce the risk of breast cancer. SERMs maybe classified according to their core structure, which is typically a variation of the 17 beta-estradiol template and sub-classified according to the side chain at the helix 12 affector region. The best known are the triphenylethylenes such as tamoxifen, used in the management of breast cancer. However, the clinical application of this class of SERMs has been limited due to endometrial stimulation. A second class is the benzothiophenes such as raloxifene and arzoxifene, which have skeletal benefit with little, if any, uterine stimulation.
In a study conducted by Christodoulakis et al, “raloxifene users did not exhibit any difference with respect to sex steroids and HOMA-IR levels.”
Raloxifen increased serum testosterone but reduced serum IGF-1 in a study performed by Duschek et al:
In aging men serum levels of testosterone and insulin-like growth factor-1 (IGF-1) decline, potential factors in the reduced muscle strength, abdominal obesity, sexual dysfunction and impaired general well being of aging. The partial estrogen agonist and antagonist raloxifene increase serum testosterone levels in aging men, but the effect of raloxifene on serum IGF-1 levels in men is unknown. In this study the effects of raloxifene on IGF-1 levels and the associated increase in serum testosterone were compared to the effects of oral testosterone supplementation…. RESULTS: Compared to placebo raloxifene increased serum testosterone by 20% but it decreased serum IGF-1 levels by 24.5% (95% confidence interval (CI): -13.0 to -36.1%). No significant change in serum IGFBP-3 levels was found. The effect of raloxifene on serum IGF-1 has been observed with other oral estrogens, and, therefore, is likely to be ascribed to the partial estrogen agonist activity of raloxifene.
According to Nordt et al, raloxifen may hold potential as an intervention in adolescent gynecomastia: “Newer treatment strategies, such as the antiestrogen raloxifene, have shown promising results; however, further studies are needed to determine long-term efficacy. As a result of the limited pharmaceutical treatment options, many more adolescents are seeking surgical intervention.”
As the title of the study suggests, raloxifen is also a promising treatment for male osteoporosis:
Raloxifene has been shown to increase bone mineral density of the hip in men receiving androgen deprivation therapy for prostate cancer. Moreover, experimental data demonstrated dramatic increase in cell death in human prostate cancer cell lines after the treatment with raloxifene. All these observations suggest that SERMs may be useful for the prevention and treatment of osteoporosis not only in postmenopausal women but also in elderly men. However, our hypothesis should be tested in a proper designed clinical trial.
Kastelan goes on to write that there are still issues of dose and duration to be assessed by further clinical study, as well as more markers of health and physical balance to be weighed against the benefits of raloxifen treatment.