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Ana4.6
Anastrozole Research
Mostly mechanism / observationalLimited safety
8 peer-reviewed studies
What the evidence says
Mostly mechanism / observational
Most Anastrozole studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from medium-quality meta-analyses and randomised trials published 2005–2024 with a typical study size of 69 participants.
Based on 8 studies · 1 meta-analysis · 7 RCTs · 7,867 total participants
Confidence
High
By outcome
Testosterone & male hormones
Mostly mechanism / observational6 studies
Bone health (trade-off)
Mostly mechanism / observational3 studies
Breast cancer (approved)
Too few graded studies2 studies
Safety profile
Too few graded studies2 studies
Fertility & reproductive
Too few graded studies1 study
Steady research
1 study in the last 5 years · Latest meta-analysis: 2024
200520142024
1RCTn=6,241 · very large study2010
Anastrozole significantly improved disease-free survival, time to recurrence, and time to distant recurrence versus tamoxifen, but fractures were more frequent during active anastrozole treatment.
Anastrozole administration normalized androgen production in older hypogonadal men and decreased estradiol production modestly; these alterations did not improve body composition or strength.
Burnett-Bowie, Roupenian, Dere, Lee, Leder · Clinical endocrinology (2009)
1-year double-blind, placebo-controlled RCT in older hypogonadal men (n=88)
In older men, aromatase inhibition increases testosterone, decreases estradiol, and appears to decrease bone mineral density; it does not improve skeletal health in aging men with low or low-normal testosterone.
Burnett-Bowie, McKay, Lee, Leder · The Journal of clinical endocrinology and metabolism (2009)
1-year double-blind, placebo-controlled RCT in older men with low testosterone (n=69)
Anastrozole raised testosterone and lowered estradiol but DECREASED posterior-anterior spine BMD vs placebo (p=0.0014)
Mandatory counter-evidence: estrogen is required for the male skeleton — suppressing it harms bone
There is insufficient evidence to support the routine use of clomiphene, tamoxifen, and aromatase inhibitors to optimise semen parameters in men with infertility.
This proof-of-concept study confirms that aromatization of testosterone is required for maintaining bone mineral density in older men with low-testosterone levels.
Short-term administration of anastrozole decreases serum estradiol in elderly men with mild hypogonadism but does not adversely affect bone metabolism over a 12-week period, and may prove a valuable method of normalizing testosterone.
Leder, Finkelstein · Osteoporosis international (2005)
12-week randomized, placebo-controlled trial in elderly mildly hypogonadal men (n=37)
Anastrozole substantially raised bioavailable testosterone and modestly lowered estradiol
Over 12 weeks, bone-turnover markers and BMD were unchanged — early-outcome anchor for the hormonal effect
Although AI plus weight loss is effective in reversing the hormonal profile of hypogonadism in severely obese men without causing major side effects, it does not lead to greater improvements in muscle strength and symptoms compared to weight loss alone.
A combination of recombinant human growth hormone and anastrozole, started at the very end of puberty, seems to allow boys with idiopathic short stature to reach a greater adult height than growth hormone alone.
Rothenbuhler, Linglart, Bougnères · International journal of pediatric endocrinology (2015)
Prospective randomized pilot trial in adolescent boys with idiopathic short stature (n=24)