Table 3.
Association between menstrual cycle length and hormonal patterns using nonlinear mixed models with harmonic terms in the BioCycle Study
| Mean (%)a |
Amplitudeb |
Phase Shift (days)c |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Estimate | 95% CI | Estimate | 95% CI | Estimate | 95% CI | ||||
| Estradiol | |||||||||
| Short (<26 d) | |||||||||
| Unadjusted | 7.84 | 1.03 | 15.11 | −0.04 | −0.08 | 0.01 | −0.88 | −1.29 | −0.49 |
| Adjustedd | 5.83 | −0.91 | 13.04 | −0.05 | −0.08 | 0.01 | −0.76 | −1.20 | −0.36 |
| Normal (26–35 d) | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| Long (>35 d) | |||||||||
| Unadjusted | −8.34 | −17.44 | 1.77 | −0.07 | −0.13 | 0.01 | 3.44 | 2.94 | 3.88 |
| Adjusted | −7.90 | −16.98 | 2.16 | −0.08 | −0.12 | 0.00 | 3.09 | 2.82 | 3.21 |
| Progesterone | |||||||||
| Short (<26 d) | |||||||||
| Unadjusted | 2.29 | −4.39 | 9.45 | 0.04 | −0.04 | 0.13 | −0.47 | −0.80 | −0.16 |
| Adjusted | 2.78 | −4.16 | 10.23 | −0.01 | −0.06 | 0.07 | −0.41 | −0.80 | −0.11 |
| Normal (26–35 d) | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| Long (>35 d) | |||||||||
| Unadjusted | −18.65 | −27.68 | −8.48 | −0.26 | −0.38 | −0.13 | 0.67 | 0.19 | 1.11 |
| Adjusted | −18.37 | −27.48 | −8.12 | −0.19 | −0.26 | −0.09 | 0.62 | 0.19 | 0.89 |
| LH | |||||||||
| Short (<26 d) | |||||||||
| Unadjusted | −13.21 | −20.05 | −5.79 | 0.03 | −0.02 | 0.09 | −1.02 | −1.42 | −0.62 |
| Adjusted | −12.49 | −19.39 | −5.00 | 0.01 | −0.01 | 0.06 | −0.71 | −1.04 | −0.39 |
| Normal (26–35 d) | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| Long (>35 d) | |||||||||
| Unadjusted | 22.29 | 7.35 | 39.32 | −0.11 | −0.17 | −0.02 | 3.32 | 2.68 | 3.92 |
| Adjusted | 20.43 | 5.99 | 36.83 | −0.06 | −0.09 | −0.002 | 2.66 | 2.23 | 2.96 |
| FSH | |||||||||
| Short (<26 d) | |||||||||
| Unadjusted | 0.11 | −6.27 | 6.94 | 0.00 | −0.04 | 0.05 | −0.65 | −1.00 | −0.28 |
| Adjusted | −3.09 | −9.23 | 3.47 | −0.01 | −0.02 | 0.03 | −0.54 | −0.89 | −0.15 |
| Normal (26–35 d) | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. |
| Long (>35 d) | |||||||||
| Unadjusted | 13.78 | 2.11 | 26.79 | −0.07 | −0.15 | 0.04 | 0.92 | 0.29 | 1.58 |
| Adjusted | 15.60 | 4.02 | 28.48 | −0.04 | −0.07 | 0.03 | 1.13 | 0.46 | 1.81 |
Boldface indicates significance at the α = 0.05 level. All models take repeated measures and correlated cycles into account. Ref., Reference.
Ratios were obtained from the model to compare the mean hormone concentrations across the menstrual cycle for short and long cycles to the normal cycle length group. Estimates of the percentage difference in the hormone level and 95% CI were obtained by subtracting 1 from each ratio and multiplying by 100.
Amplitude differences are interpreted as the difference in peak hormone levels as compared to the normal length category.
Phase shift differences are interpreted as the difference in the number of days of a standardized 28-d cycle between the rise in hormone concentrations as compared to the normal length category (e.g. 1.12 = hormone rise is shifted 1.12 d later).
Models are adjusted for age, race, and BMI. Anovulatory cycles were excluded from this analysis (n = 42 cycles).