Hormonal contraception

Hormonal contraception refers to birth control methods that act on the hormonal system.

Currently, all hormonal contraceptives are designed for use by women rather than men, though research on a male hormonal contraceptive (“the male Pill”) has been underway for some time.

Hormonal contraceptives may be introduced into the woman’s body in many different ways, among them orally, vaginally, transdermally, or through injections or implants. The oral method was the first and most famous of these; within a few years of its introduction in 1960, "the Pill" became one of the most popular contraceptives in the United States and elsewhere, and it remains so today.

Hormonal contraception may act in one or more ways to prevent pregnancy. It may cause ovulation to cease, preventing the possibility of fertilization; it may thicken the woman’s cervical mucus, making penetration of the uterus by sperm more difficult; or it may alter and thin the endometrium so that a fertilized egg has difficulty implanting. (Technically, if the drug works in this third fashion, it acts as a contragestive rather than a contraceptive, since it has not prevented conception, acting instead to prevent gestation.)

Advantages and disadvantages
Because hormonal contraception represents a large group of diverse products, the advantages and disadvantages differ between different formulations. Generally speaking, if used properly, hormonal contraceptives are highly effective; except for abstinence, intrauterine device, vasectomy, and tubal ligation, no other method of birth control has as great a degree of effectiveness. Hormonal contraceptives also allow spontaneous intercourse.

On the other hand, hormonal contraceptives offer no protection against sexually transmitted infections. Like many other forms of birth control, hormonal contraceptives rely on the woman to use them correctly. Some, such as implants, require relatively little attention; others, such as injections or transdermal patches, require a schedule ranging from a week to several months. Still others—the wide varieties of oral contraception require a daily schedule. For example, many patient information leaflet for these pharmaceuticals suggest using a back up method of birth control if 2 or more doses are missed. Information on the side effects and serious health risks can be located on the specific formulation's patient information leaflet. Finally, artificial contraception is objectionable to some religious traditions. These objections are furthered by the suggested, yet unproven post-fertilisation mode of action of preventing the implantation of a blastocyst.

Effects on rates of cancers
There is a mixed effect of combined hormonal contraceptives on the rates of various cancers, with the International Agency for Research on Cancer (IARC) concluding that "Combined oral contraceptives are carcinogenic to humans" and that "there is also conclusive evidence that these agents have a protective effect against cancers of the ovary and endometrium":
 * The (IARC) note that "the weight of the evidence suggests a small increase in the relative risk for breast cancer among current and recent users" which following discontinuation then lessens over a period of 10 years to similar rates as women who never used them.
 * Small increases are also seen in the rates of cervical cancer and hepatocellular (liver) tumours.
 * Endometrial and ovarian cancer risks are approximately halved and persists for at least 10 years after cessation of use; although "sequential oral contraceptives which were removed from the consumer market in the 1970s was associated with an increased risk for endometrial cancer".
 * Studies have overall not shown effects on the relative risks for colorectal, malignant melanoma or thyroid cancers.
 * Information on progesterone-only pills is less extensive, due to smaller sampling sizes, but they do not appear to significantly increase the risk of breast cancer.
 * Most other forms of hormonal contraception are too new for meaningful data to be available, although risks and benefits are believed to be similar for methods which use the same hormones; e.g., risks for combined-hormone patches are thought to be roughly equivalent to those for combined-hormone pills.

Oral contraceptives

 * Combined oral contraceptive pill: known colloquially as "The Pill", it is a combined estrogen and progesterone pill which is taken daily at the same time.
 * Progesterone only pill (POP)

Most combined and progesterone-only pills may also be taken in high doses as emergency contraception (also known as the morning after pill). However, unlike plain copper IUDs, hormonal IUS is not approved for emergency contraception.

Non-surgical devices

 * Contraceptive patch: an adhesive patch containing hormones which is applied to the skin and worn continuously. It is changed each week for three weeks and removed for one week.
 * Contraceptive vaginal ring ("NuvaRing"): a flexible ring containing estrogen and progesterone, it is inserted into the vagina and worn for three continuous weeks, removed for one week, then replaced with a new ring.

Intrauterine devices

 * Progesterone IntraUterine System: otherwise known as the IUS, this device is inserted into the uterus by a health care professional, where it continuously releases progesterone. It remains in the uterus for a period of years, as determined by the manufacturer.

Injections

 * Combined injectable contraceptive: a monthly injection of progesterone and estradiol; one brand, Lunelle was discontinued in 2002 and not currently available for sale in the U.S.
 * Depo Provera: an injection of progesterone administered every three months.

Surgical devices

 * Implants: one or more flexible rods containing progesterone, which are implanted under the skin. Norplant, an implant of this type, is being phased out of production, Jadelle was approved in 1996, and Implanon was approved in July 2006.

Ormeloxifene
Ormeloxifene (a.k.a. Centchroman) is sometimes mistaken for a hormonal contraceptive, probably because it is a pill that prevents pregnancy. Although it may be correctly termed a 'weekly contraceptive pill', it is not a hormonal contraceptive. Ormeloxifene is a selective estrogen receptor modulator, or SERM. It causes ovulation to occur sooner than it normally would, while causing the lining of the uterus to build more slowly, which, together, prevent pregnancy. Ormeloxifene is legally available only in India.