Association of Serum Sex Steroid Hormone Hemodilution and Body Mass Index Among Healthy Postmenopausal Women

PurposeHemodilution refers to reduced concentrations of analytes in the blood secondary to increased fluid volume. Given that obesity is associated with expanded vascular volume, hemodilution may result in a lower ratio of blood concentrations of analytes among heavier subjects. Assessing the relationship of hormone concentration to total mass varies by body mass index (BMI) is etiologically important because obesity is related to hormone metabolism and cancer risk.MethodsWe evaluated data for 194 postmenopausal controls in an endometrial cancer case-control study. Height, weight, and serum hormone concentrations were measured previously. We estimated serum hormone mass from concentration based on estimates of calculated plasma volume. We assessed the effect of BMI on relationships of sex steroid hormone concentration and mass using multivariate linear regression.ResultsHigher BMI was associated with increased estrone, estrone sulfate, estradiol, and albumin-bound estradiol concentrations and masses (p-trend ≤ 0.001). With increasing BMI, androstenedione concentration did not change significantly (p-trend = 0.548), but its mass increased (p-trend = 0.024).ConclusionsRelationships of sex steroid hormone concentration and mass were generally similar, except for androstenedione in which the relationship was only significant for mass. Future studies to assess both sex steroid hormone concentration and mass may have value in etiological research.