Table 2.

Multivariate-adjusteda geometric means of estrogen metabolism measures by quartiles of caffeine intake

Geometric mean by caffeine intake
<49 mg/d49–163 mg/d164–366 mg/d≥367 mg/dPtrend
N144144144145
Individual and grouped EM (pmol/mg creatinine)
Total EM199.0183.4203.5211.00.10
Parent estrogens40.839.440.541.30.67
 Estrone26.825.426.427.40.54
 Estradiol13.212.812.913.50.66
Catechols67.861.562.374.60.19
 2-catechols56.753.053.165.30.10
  2-Hydroxyestrone50.046.846.557.90.10
  2-Hydroxyestradiol5.85.45.66.50.14
 4-catechols
  4-Hydroxyestrone7.65.75.96.20.28
Methylated catechols11.410.910.110.50.28
 Methylated 2-catechols11.110.69.710.10.25
  2-Methoxyestrone8.78.27.67.80.18
  2-Methoxyestradiol0.780.700.710.690.29
  2-Hydroxyestrone-3-methyl ether1.41.31.21.30.18
 Methylated 4-catechols0.250.230.220.250.91
  4-Methoxyestrone0.150.150.130.180.37
  4-Methoxyestradiol0.060.050.060.050.45
2-Hydroxylation pathway70.164.864.076.70.25
4-Hydroxylation pathway8.36.86.67.20.39
16-Hydroxylation pathway62.361.067.365.30.33
16α-Hydroxyestrone9.710.111.212.40.01
 Estriol27.526.430.626.21.00
 17-Epiestriol1.61.71.71.60.96
 16-Ketoestradiol12.212.614.213.70.07
16-Epiestriol5.35.45.96.00.04
Ratios (pmol/pmol)
2-Hydroxyestrone/16α-hydroxyestrone5.04.64.04.50.29
4-Pathway/2-pathway0.110.100.100.090.01
2-Pathway/16-pathway1.11.00.91.20.69
2,4-Pathway/16-pathway0.130.110.090.110.15
2-Catechols/methylated 2-catechols5.04.95.46.30.0002
4-Catechols/methylated 4-catechols31.725.927.226.80.53
Catechols/methylated catechols5.85.56.17.00.001
Parent estrogens/2-, 4-, 16-pathways0.280.280.260.250.03
2-Pathway/parent estrogens1.71.61.51.80.23
4-Pathway/parent estrogens0.200.170.160.170.20
16-Pathway/parent estrogens1.51.61.71.60.50
  • aAdjusted for age at urine collection (continuous), BMI at collection (kg/m2, continuous), height (continuous), ovulatory cycle (yes/no), first-morning urine (yes/no), quartiles of alcohol intake (nondrinker, ≤1.49, 1.50–4.85, >4.85 g/day), total physical activity (<3, 3–8.9, 9–17.9, 18–26.9, 27–41.9, ≥42 MET h/wk), current tobacco use (yes/no), luteal day (≤5, 6–7, 8–9, ≥10 days to next period), usual menstrual cycle length (<26, 26–31, ≥32 days), menstrual cycle regularity (extremely regular, very regular, regular, usually/always irregular), and age at first birth and parity (nulliparous, age at first birth <25 years/1–2 children, age at first birth 25–29 years/1–2 children, age at first birth ≥30 years/1–2 children, age at first birth <25 years/≥3 children, age at first birth ≥25 years/≥3 children). Numbers do not sum to 603 due to missing values for exposure. Significant Ptrend shown in bold.