Fig. 4: Geometric mean concentrations of total oestradiol by phase of the menstrual cycle in pre-menopausal women.

Menstrual cycle phases were defined by forward dating as early follicular = days 0–5, late follicular = days 6–10, mid-cycle = days 11–14, early luteal = days 15–18, mid-luteal = days 19–24 and late luteal = days ≥25.