Pituitary and ovarian hormone activity during the 7-day hormone-free interval of various combined oral contraceptive regimens

Objective: The objective was to investigate changes in luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E₂) and progesterone (P) during the hormone-free interval (HFI) of 6 combined oral contraceptives (COCs). Design: Blood samples were obtained from 62 women. Results: When COCs were grouped by ethinyl estradiol (EE) dose, there was a significant positive mean slope for LH and FSH during the HFI for the 30- and 35 mcg-EE doses, whereas 20 showed a gradual nonsignificant slope. All E ₂ slopes were significant. P remained suppressed with all doses. Conclusion: A more rapid rebound of gonadotropin levels is found with higher doses of EE during the HFI. Implications: This study showed a more rapid rebound of pituitary hormone levels among women using higher-EE-dosage formulations, which was demonstrated by the statistically significant slope for mean LH and FSH from day 1 to day 7 of the HFI. The degree of suppression did not vary across progestin generations. It remains to be established whether women who experience side effects during their HFI may benefit from using a COC with a lower EE dose to minimize changes in endogenous pituitary hormone levels.