Lignan and isoflavone excretion in relation to uterine fibroids: a case-control study of young to middle-aged women in the United States.
BACKGROUND
Uterine fibroids are hormonally responsive; estradiol and progesterone stimulate their growth, and gonadotrophin-releasing hormone agonists shrink them. Phytoestrogens, including isoflavones and lignans, can act as weak estrogens or antiestrogens.


OBJECTIVE
The objective of this case-control study was to evaluate the relation between uterine fibroid risk and phytoestrogen exposure.


METHODS
Two overnight urine collections (48 h apart) from 170 uterine fibroid cases and 173 controls were analyzed for isoflavonoids (ie, daidzein, genistein, equol, and O-desmethylangolensin) and lignans (enterodiol and enterolactone). Logistic regression was used to determine associations between the mean excretion of the 2 collections and the risk of uterine fibroids.


RESULTS
Unadjusted isoflavone excretion did not differ significantly between cases and controls (2.33 +/- 5.82 and 2.60 +/- 5.90 nmol/mg Cr, respectively; P = 0.68), but cases excreted significantly less lignans than did controls (2.86 +/- 3.45 and 4.57 +/- 6.67 nmol/mg Cr, respectively; P < 0.01). The trend for a reduced risk of uterine fibroids with increasing quartiles of lignan excretion was significant (odds ratio for highest versus lowest quartile = 0.31; 95% CI: 0.17, 0.58; P for trend < 0.01). When adjusted for age, BMI, race, family history of uterine fibroids, and isoflavone excretion, this trend remained but was attenuated (P = 0.07).


CONCLUSIONS
Our findings suggest a modest inverse association between lignan excretion and uterine fibroid risk. Whether this relation represents an effect of lignans per se or of other constituents of lignan-containing foods on the development of uterine fibroids remains to be determined. No association was found between isoflavone excretion and uterine fibroids; however, the intake of soy foods, the primary source of isoflavones, was low in this population.
Atkinson
Charlotte
C
Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
Lampe
Johanna W
JW
Scholes
Delia
D
Chen
Chu
C
Wähälä
Kristiina
K
Schwartz
Stephen M
SM
D000328:Adult; D015415:Biomarkers / Q000652:urine; D016022:Case-Control Studies; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000652:urine*; D007889:Leiomyoma / Q000453:epidemiology / Q000652:urine*; D017705:Lignans / Q000652:urine*; D016014:Linear Models; D008875:Middle Aged; D016017:Odds Ratio; D048789:Phytoestrogens / Q000652:urine; D012307:Risk Factors; D013025:Glycine max / Q000737:chemistry; D014481:United States / Q000453:epidemiology
D015415:Biomarkers; D007529:Isoflavones; D017705:Lignans; D048789:Phytoestrogens