Jonathan I. Epstein, Alan W. Partin, Inpakala Simon,
INTRODUCTION: A mechanism of action of saw palmetto extract (SPE) in human prostate is unknown. Suggested mechanisms include inhibition of androgen action and an anti-inflammatory effect. We evaluated these possibilities by study of prostate biopsy specimens obtained before and after treatment from men in a 6-month randomized clinical trial of SPE vs. placebo.
METHODS: Patient characteristics and study design are described in the companion abstract. Ultrasound-guided sextant biopsy for tissue study was available on 41 men, performed at baseline and after 6 months of placebo (N=20) or SPE (N=21). The 82 tissue samples were batch-studied by routine histology; by morphometry for quantitative tissue composition of the inner and outer gland; by use of a histopathologic scoring system for inflammation, acute and chronic, and for atrophy; by immunohistochemical assessment of apoptosis, cell proliferation, and androgen receptor expression; and by a tissue homogenate radioimmunoassay for testosterone and dihydrotestosterone (expressed as ng/g of prostate tissue).
RESULTS: A contraction in the transition zone epithelium, from 17.8% before to 10.7% after 6 months of treatment, was found in the SPE group (p<0.01). In a parallel, independent analysis, the epithelial atrophy score increased from 25.2% before to 40.9% after SPE (p<0.01). In placebo patients, no significant changes were seen in any tissue measures. None of the other tissue studies revealed significant changes from baseline during SPE treatment.
CONCLUSIONS: SPE appears to exert a suppressant effect on the prostatic epithelium, especially in the TZ. Since no alteration in prostatic androgen metabolism or apoptosis markers could be demonstrated, the data suggest that the effect is mediated by some non-hormonal control mechanism. How epithelial suppression relates to clinical effects, in the absence of prostate volume contraction, is not clear. However, the finding that use of SPE can in 6 months lead to a statistically significant epithelial involution in the human prostate should serve as an impetus to further investigation.