Table 2. Association between plasma oestradiol, testosterone and SHBG levels and percentage mammographic density among control subjects: Breakthrough Generations Study, United Kingdom.
| |
Percentage mammographic density (%), quartilesa |
|
||||
|---|---|---|---|---|---|---|
| Characteristic | 1st | 2nd | 3rd | 4th | % Increase per quartileb | P-value trendb |
| No. of controls |
84 |
83 |
84 |
83 |
|
|
| Median percentage density (%) |
3.2 |
11.8 |
22.2 |
40.2 |
|
|
| Mean age at mammogram (years) |
62.0 |
60.8 |
60.7 |
60.6 |
|
|
| Mean BMI at cohort entry (kg m−2) |
28.0 |
25.4 |
26.5 |
24.1 |
|
|
|
Geometric mean, adjusted for laboratory batch and age at mammogram | ||||||
| Oestradiol (pmol l−1) | 22.6 | 19.9 | 20.8 | 15.6 | −10.0 | <0.001 |
| Free oestradiol (pmol l−1) | 0.55 | 0.47 | 0.49 | 0.35 | −12.4 | <0.001 |
| Testosterone (nmol l−1) | 0.64 | 0.56 | 0.62 | 0.53 | −4.3 | 0.205 |
| Free testosterone (nmol l−1) | 0.010 | 0.008 | 0.009 | 0.007 | −9.3 | 0.009 |
| SHBG (nmol l−1) |
37.3 |
42.3 |
42.5 |
51.0 |
9.9 |
<0.001 |
|
Geometric mean, additionally adjusted for BMI | ||||||
| Oestradiol (pmol l−1) | 19.7 | 20.8 | 20.2 | 17.9 | −3.2 | 0.261 |
| Free oestradiol (pmol l−1) | 0.47 | 0.49 | 0.48 | 0.41 | −4.6 | 0.114 |
| Testosterone (nmol l−1) | 0.62 | 0.57 | 0.62 | 0.56 | −1.7 | 0.638 |
| Free testosterone (nmol l−1) | 0.009 | 0.008 | 0.009 | 0.007 | −4.6 | 0.202 |
| SHBG (nmol l−1) | 39.9 | 41.5 | 43.1 | 47.8 | 5.9 | 0.006 |
Abbreviations: BMI=body mass index; SHBG=sex hormone-binding globulin.
a
Q1: <6.58; Q2: 6.58–16.75; Q3: 16.76–29.60; Q4: >29.60 percentage density.
b
Percentage change in sex hormone or SHBG level per quartile increase in percentage mammographic density, P-value based on Wald test.