Raloxifene is the next-generation of selective estrogen receptor modulators. Raloxifene, like other SERMs, acts as an estrogen receptor agonist in some tissues but as an antagonist (or partial agonist) in others1. Raloxifene is used in post-menopausal women to help prevent osteoporosis since it is an active estrogen in bone. It is also an agonist with regard to its ability to lower LDL and total cholesterol levels. Raloxifene acts as an antagonist in breast and uterine tissues. Raloxifene is newer so it has not been used much for this purpose in men. Unlike tamoxifen, raloxifene is not available in generic form which makes it more expensive. Studies have shown raloxifene to be better than tamoxifen in treatment of gynecomastia with a greater response rate and degree of response2. Raloxifene has also been shown to increase LH, FSH, SHBG and total and free testosterone in males3. Even though raloxifene appears to be a better choice than tamoxifen, it is unlikely that its use will increase until it is available as a generic. Tamoxifen and clomid may not be as good, but they are cheap and readily available. There has been some talk of estrogen antagonists reducing IGF-1 and the effect that this could have on skeletal muscle hypertrophy. Aromatase inhibitors have been shown to increase IGF-1 levels4,5. SERMS on the other hand have been shown to decrease IGF-1 levels.
The fact is, serum IGF-1 levels do not have any correlation with muscle growth but rather, it is the release of IGF-1 within the muscle that has an anabolic effect. Increasing circulating IGF-1 levels may actually be detrimental and promote tumor growth6. As discussed later, the IGF-1 system is very complex with multiple binding proteins that modulate its actions so simply elevating circulating levels doesn’t mean much in and of itself.
1. Heringa M: Review on raloxifene: profile of a selective estrogen receptor modulator. Int J Clin Pharmacol Ther. Aug;41(8):331-45, 2003
2. Lawrence SE, Faught KA, Vethamuthu J, Lawson ML: Beneficial effects of raloxifene and tamoxifen in the treatment of pubertal gynecomastia. J Pediatr. Jul;145(1):71-6, 2004
3. Duschek EJ, Gooren LJ, Netelenbos C: Effects of raloxifene on gonadotrophins, sex hormones, bone turnover and lipids in healthy elderly men. Eur J Endocrinol. Apr;150(4):539-46, 2004
4. Bajetta E, Ferrari L, Celio L, Mariani L, Miceli R, Di Leo A, Zilembo N, Buzzoni R, Spagnoli I, Martinetti A, Bichisao E, Seregni E. The aromatase inhibitor letrozole in advanced breast cancer: effects on serum insulin-like growth factor (IGF)-I and IGF-binding protein-3 levels. J Steroid Biochem Mol Biol. 63(4-6):261-7, 1997
5. Ferrari L, Martinetti A, Zilembo N, Pozzi P, Buzzoni R, La Torre I, Gattinoni L, Catena L, Vitali M, Celio L, Seregni E, Bombardieri E, Bajetta E. Short-term effects of anastrozole treatment on insulin-like growth factor system in postmenopausal advanced breast cancer patients. J Steroid Biochem Mol Biol. 80(4-5):411-8, 2002
6. Renehan AG, Zwahlen M, Minder C, O’Dwyer ST, Shalet SM, Egger M. Insulin-like growth factor (IGF)-I, IGF binding protein-3, and cancer risk: systematic review and meta-regression analysis. Lancet. 363(9418):1346-53, 2004