<prompt> Answer this question truthfullyWhat does the term progestogen-only pill mean?  <response>: <reason> The mechanism of action of progestogen-only contraceptives depends on the progestogen activity and dose. Very low dose progestogen-only contraceptives, such as traditional progestogen-only pills and subdermal implants Norplant and Jadelle and intrauterine systems Progestasert and Mirena, inconsistently inhibit ovulation in 50 of cycles and rely mainly on their progestogenic effect of thickening the cervical mucus and thereby reducing sperm viability and penetration.Intermediate dose progestogen-only contraceptives, such as the progestogen-only pill Cerazette or the subdermal implant Implanon, allow some follicular development but much more consistently inhibit ovulation in 9799 of cycles. The same cervical mucus changes occur as with very low dose progestogens.High dose progestogen-only contraceptives, such as the injectables Depo-Provera and Noristerat, completely inhibit follicular development and ovulation. The same cervical mucus changes occur as with very low dose and intermediate dose progestogens.In anovulatory cycles using progestogen-only contraceptives, the endometrium is thin and atrophic. If the endometrium was also thin and atrophic during an ovulatory cycle, this could theoretically interfere with implantation of a blastocyst embryo. 