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Articles by B. L Egleston
Total Records ( 2 ) for B. L Egleston
  B. L Egleston , D. W Chandler and J. F. Dorgan
  Background

Circulating levels of bioavailable oestradiol and testosterone are often desirable for clinical practice or investigational studies of children. However, assays to measure circulating hormone levels might not always be accessible. We sought to validate the empirical calculation of circulating bioavailable testosterone and oestradiol in children.

Methods

Six hundred and sixty-three eight- to 10-year olds were recruited to the Dietary Intervention Study in Children (DISC). DISC was a randomized clinical trial designed to test efficacy of a dietary intervention to reduce serum cholesterol (LDL-C) in children with elevated cholesterol. Assay measures of oestradiol, testosterone, sex hormone-binding globulin concentration (SHBG) and albumin concentration in girls as well as dihydrotestosterone in boys were measured for up to 10 y. We calculated measures of circulating non-SHBG bound oestradiol and testosterone from total hormone levels using the law of mass action. We compared proportional differences in assay measured minus calculated non-SHBG bound hormone levels versus their averages using generalized estimating equations-estimated linear regressions.

Results

On average, calculated values overestimated assay measured values (–11.7% for non-SHBG bound oestradiol in girls and –2.6% for non-SHBG bound testosterone in boys). The intercept and slope of the regression for non-SHBG bound oestradiol in girls were –0.13 (95% confidence interval [CI] –0.14 to –0.12) and 0.005 (95% CI 0.003–0.007), respectively. The intercept and slope for non-SHBG bound testosterone in boys were –0.16 (95% CI –0.17 to –0.14) and 0.0006 (95% CI 0.0005–0.0006).

Conclusion

While calculated values might be useful for research purposes, they are generally not close enough for clinical purposes.

  J. F Dorgan , F. Z Stanczyk , B. L Egleston , L. L Kahle , C. M Shaw , C. S Spittle , A. K Godwin and L. A. Brinton
  Background

Müllerian inhibiting substance (MIS) is a member of the transforming growth factor β family of growth and differentiation factors that inhibits elongation and branching of mammary ducts and has been shown to inhibit mammary tumor growth in vitro and in animal models. The objective of this study was to determine whether serum MIS levels are associated with breast cancer risk.

Methods

We conducted a prospective case–control study of 309 participants who were registered in the Columbia, Missouri Serum Bank. Each of 105 in situ or invasive breast cancer case patients with prediagnostic serum collected before menopause was matched to two control subjects by age, date, menstrual cycle day, and time of day of blood collection. MIS was measured in serum by using an enzyme-linked immunosorbent assay, and estradiol and testosterone concentrations were quantified by using specific radioimmunoassays. Data were analyzed using conditional logistic regression. All tests of statistical significance were two-sided.

Results

The relative odds ratio of breast cancer for women in increasing MIS quartiles were 1, 2.8 (95% confidence interval [CI] = 1.0 to 7.4), 5.9 (95% CI = 2.4 to 14.6), and 9.8 (95% CI = 3.3 to 28.9, Ptrend < .001). The association of MIS with breast cancer was weaker in women who were not taking oral contraceptives at the time of blood collection, but adjustment for estradiol and testosterone levels did not materially alter results for these women. The association of MIS with breast cancer did not vary by age at blood collection but was stronger among women who were diagnosed with breast cancer at an older age than among those who were diagnosed at a younger age.

Conclusion

MIS may be a novel biomarker of increased breast cancer risk. Additional research including confirmatory epidemiological studies and mechanistic studies is needed.

 
 
 
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