The degree of suppression and subsequent activation of the hypothalamic-pituitary-ovarian
axis during the hormone-free interval in combined oral contraceptive (COC) hormone users
varies depending on the dose of ethinyl estradiol in the formulation. This variation in
activation may be associated with different side effects during the hormone free interval.
Progesterone (P) remained suppressed during all 6 COC regimens (<1.8 ng/mL), which indicates
continuous contraceptive efficacy during the 7-day hormone free interval of all formulations
studied.