Background: Adult height and insulin are thought to modify the development of breast cancer. However, little is known about the association between height and 17beta-estradiol, a key factor in breast carcinogenesis, and whether insulin modifies such an association.
Methods: Among 204 healthy women, ages 25 to 35 years, who participated in the Energy Balance and Breast Cancer Aspect I study, adult height (in centimeters) and fasting serum concentrations of insulin (pmol/L) were measured. 17beta-Estradiol concentrations were measured in daily saliva samples throughout an entire menstrual cycle through RIA. Age and multivariate linear regression models were used to study the association between adult height and 17beta-estradiol levels throughout an entire menstrual cycle and whether serum levels of fasting insulin may modify such an association.
Results: The women had a mean age of 30.7 years, adult height of 166.9 cm, and serum insulin of 85.7 pmol/L. For each increase of one SD in insulin levels in the upper tertile of adult height, the adjusted level of 17beta-estradiol increased by 3.1 pmol/L (95% confidence interval, 1.1-5.2), equivalent to a 17.3% higher mean average concentration of 17beta-estradiol. Women with an adult height > or =170 cm (upper tertile) and insulin levels >101 pmol/L (upper quartile) experienced, on average, 41% higher 17beta-estradiol levels throughout the entire menstrual cycle compared with women with the same adult height and insulin levels <101 pmol/L.
Conclusion: Our findings support that premenopausal levels of 17beta-estradiol vary in response to adult height and insulin levels, of possible importance for breast cancer risk.