TABLE 6.
Thyroid hormone concentrations at baseline and change from baseline at 2–18 mo of study1
| Δ, % | ANOVA2P | Trend2P | ANCOVA3P | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Parameter | Group | Baseline | 2 mo | 4 mo | 8 mo | 12 mo | 18 mo | |||
| Triiodothyronine, ng/mL | Soy | 1.02 (0.87, 1.17) | 6.56 (–2.23, 15.53) | 4.05 (–3.49, 11.59) | 3.79 (–6.59, 14.19) | 6.38 (–6.59, 19.34) | 5.99 (–1.89, 13.88) | 0.696 | 0.430 | 0.948 |
| Placebo | 1.01 (0.83, 1.19) | 4.47 (–5.79, 14.72) | 1.68 (–7.74, 11.10) | 5.64 (–5.88, 17.15) | 4.67 (–5.44, 14.79) | 4.00 (–6.33, 14.34) | 0.861 | 0.471 | ||
| Free triiodothyronine, pg/mL | Soy | 2.99 (2.64, 3.34) | 7.53 (1.22, 13.85) | 7.42 (0.23, 14.60) | 5.52 (–2.37, 13.41) | 4.00 (–3.53, 11.53) | 8.65 (1.16, 16.14) | 0.189 | 0.221 | 0.940 |
| Placebo | 2.74 (2.34, 3.14) | 7.48 (–4.52, 19.47) | 3.55 (–11.04, 18.13) | 7.40 (–3.34, 18.14) | 4.02 (–5.95, 14.00) | 9.20 (–2.84, 21.24) | 0.438 | 0.158 | ||
| Thyroxine, µg/dL | Soy | 6.39 (5.80, 7.98) | –1.07 (–7.00, 4.86) | –6.66 (–25.03, 11.71) | 1.52 (–6.91, 9.95) | 6.88 (–2.92, 16.69) | 5.83 (–4.70, 16.35) | 0.396 | 0.085 | 0.6484 |
| Placebo | 6.26 (5.42, 7.11) | –1.83 (–11.54, 7.88) | 1.57 (–7.51, 10.66) | 0.28 (–9.85, 10.40) | 1.86 (–7.09, 10.81) | 6.43 (–4.22, 12.91) | 0.595 | 0.207 | ||
| Free thyroxine, ng/dL | Soy | 1.25 (1.11, 1.40) | 2.53 (–3.48, 8.53) | 2.79 (–5.27, 10.84) | 1.92 (–4.02, 7.86) | 4.42 (–3.66, 12.49) | 5.41 (0.11, 10.71) | 0.616 | 0.124 | 0.2144 |
| Placebo | 1.17 (1.05, 1.30) | 0.35 (–5.91, 6.61) | 1.30 (–4.20, 6.81) | 1.37 (–7.37, 10.11) | –0.77 (–7.58, 6.04) | 2.14 (–5.22, 9.50) | 0.944 | 0.874 | ||
| Thyrotropin, µIU/mL | Soy | 2.13 (1.30, 3.00) | –1.3 (–17.6, 14.0) | 4.9 (–16.5, 26.2) | 9.4 (–3.0, 21.9) | 10.1 (–11.4, 31.6) | 11.3 (–12.5, 35.1) | 0.674 | 0.130 | 0.856 |
| Placebo | 1.82 (1.21, 2.43) | 10.5 (–10.0, 31.1) | 22.2 (–6.1, 50.4) | 21.0 (–11.2, 53.3) | 33.6 (13.6, 53.6) | 37.1 (10.0, 64.2) | 0.022 | 0.005 | ||
Values are means (95% CIs). Only subjects without self-reported thyroid disease and/or on thyroid medication and with complete data at all time points are included. Each group consisted of 11 men. The age (mean ± SD) of the soy group was 59.3 ± 6.1 y, and that of the placebo group was 61.6 ± 8.3 y (P = 0.472; 2-sided t test).
Two-way repeated-measures ANOVA of change over time after log transformation of the data.
ANCOVA for difference in percentage change from baseline between the 2 treatments at 18 mo, with age at baseline as covariate on log-transformed data unless indicated otherwise.
The data for this ANCOVA analysis were not transformed to avoid violating required assumptions.