Anastrozole belongs to a class of compounds known as aromatase inhibitors (AIs). An enzyme known as aromatase is responsible in the human body for producing estrogen by converting androgens into estrogen. Aromatase inhibitors like Anastrozole prevent aromatase from fulfilling that role by binding to it and rendering it inactive. AIs fall into two categories: reversible (such as letrozole and Anastrozole ) and irreversible; irreversible AIs permanently bind to the circulating aromatase complex.
Anastrozole is primarily used for treating metastases in post-menopausal women and as a follow-up treatment to breast cancer surgery. Because estrogen causes growth of some cancerous breast cells, the aromatase-inhibition induced disruption of estrogen production in the body can have a beneficial therapeutic outcome on women with breast cancer
The ATAC trial (Anastrozole /Tamoxifen, Alone or Combined), an international randomized and controlled trial undertaken with 9,366 women, studied subjects with localized breast cancer who received five years of either tamoxifen, Anastrozole , or both, or neither, and followed them for an additional five years. Over the long-term, results of Anastrozole were significantly better than tamoxifen alone, leading Howell and others to conclude that Anastrozole is the long-term treatment of choice in women with local estrogen-receptor positive (ER-positive) breast cancer.
Anastrozole , like letrozole, may interfere with normal healthy bone metabolism. After two years of tamoxifen treatment, women who switched over to letrozole experienced twice as many (2.1% vs 1%) fractures as women who remained on tamoxifen.
Holbrook and Cohen's study results "suggest that aromatase inhibition with Anastrozole may provide a practical and efficacious alternative for the treatment of IHH but is not effective in preventing premature ejaculation."
Mauras et al, in a study whose "objective was to investigate whether anastrozole, a potent aromatase inhibitor, could delay bone age acceleration and increase predicted adult height in adolescent boys with GH deficiency," found that:
Anastrozole increases adult height potential of adolescent boys on GH therapy while maintaining normal pubertal progression after 2-3 yr. This treatment offers an alternative in promoting growth in GH-deficient boys in puberty. Long-term follow up is needed to elucidate fully the safety and efficacy of this approach.
Roth et al report:
A 29-year-old man presented to a clinic with infertility and hypogonadism in the setting of morbid obesity. On presentation, he had notable gynecomastia and a low testicular volume. The patient's weight was 154 kg and his height was 168 cm (BMI 54.5 kg/m(2)). Before referral to the clinic, the patient had been treated with testosterone therapy for 4 months for hypogonadism. This treatment had caused his initially low sperm concentration to fall to undetectable levels. [...] Treatment with an aromatase inhibitor, anastrozole, led to normalization of the patient's testosterone, luteinizing hormone and follicle-stimulating hormone levels, suppression of serum estradiol levels, and to normalization of spermatogenesis and fertility.
Burnette-Bowie et al found that "anastrozole administration normalized androgen production in older hypogonadal men and decreased estradiol production modestly."
Howell A, Cuzick J, Baum M, et al. Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer. Lancet 365 (9453): 60–2. 2005.
R. Jakesz et al. Review of: Arimidex After Two Years of Tamoxifen Reduces Recurrence in Post-Menopausal Women. The Lancet, August 6, 2005.
Holbrook JM, Cohen PG. Aromatase inhibition for the treatment of idiopathic hypogonadotropic hypogonadism in men with premature ejaculation. South Med J. 2003 Jun;96(6):544-7.
Mauras N, Gonzalez de Pijem L, Hsiang HY, Desrosiers P, Rapaport R, Schwartz ID, Klein KO, Singh RJ, Miyamoto A, Bishop K. Anastrozole increases predicted adult height of short adolescent males treated with growth hormone: a randomized, placebo-controlled, multicenter trial for one to three years. J Clin Endocrinol Metab. 2008 Mar;93(3):823-31. Epub 2007 Dec 28.
 Roth MY, Amory JK, Page ST. Treatment of male infertility secondary to morbid obesity. Nat Clin Pract Endocrinol Metab. 2008 Jul;4(7):415-9.
Burnett-Bowie SA, Roupenian KC, Dere ME, Lee H, Leder BZ. Effects of aromatase inhibition in hypogonadal older men: a randomized, double-blind, placebo-controlled trial. Clin Endocrinol (Oxf). 2008.
*The latter article is intended for educational / informational purposes only. THIS PRODUCT IS INTENDED AS A RESEARCH CHEMICAL ONLY. This designation allows the use of research chemicals strictly for in vitro testing and laboratory experimentation only. Bodily introduction of any kind into humans or animals is strictly forbidden by law.