Effects on serum hormone levels of low-dose estrogen in place of placebo during the hormone-free interval of an oral contraceptive

Contraception. 2008 Jan;77(1):34-9. doi: 10.1016/j.contraception.2007.09.010. Epub 2007 Nov 26.


Background: The study was conducted to evaluate the effects of low-dose estrogen compared to placebo on ovarian activity during the traditional 7-day hormone-free interval (HFI) of an oral contraceptive (OC).

Study design: Women were randomized to placebo or low-dose estrogen for 7 days during the HFI. Serum levels of estradiol, follicle-stimulating hormone (FSH), luteinizing hormone and inhibin B were obtained before, during and after treatment.

Results: Mean hormone levels remained constant or only increased slightly for the low-dose estrogen group compared to greater more sustained increases observed for the placebo group. Estradiol, FSH and inhibin B levels were substantially higher for those on placebo. Differences were most noticeable by the end of the HFI and persisted into the subsequent cycle.

Conclusion: Subjects receiving low-dose estrogen for 7 days during the HFI demonstrated more pronounced ovarian suppression compared to placebo as evidenced by attenuation of increases in serum inhibin B, FSH and estradiol levels.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Contraceptives, Oral, Hormonal / administration & dosage*
  • Contraceptives, Oral, Sequential / pharmacology*
  • Estradiol / blood
  • Female
  • Follicle Stimulating Hormone / blood
  • Humans
  • Inhibins / blood
  • Inhibins / drug effects
  • Ovary / drug effects*
  • Placebos / administration & dosage
  • Prospective Studies


  • Contraceptives, Oral, Hormonal
  • Contraceptives, Oral, Sequential
  • Placebos
  • inhibin B
  • Estradiol
  • Inhibins
  • Follicle Stimulating Hormone