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The Key Point of Hormonal Birth Control Methods and Their Mechanism of Action

As there are many positions how one can make sex depending on the stature, likes-dislikes and even to whom to give the priority - there are so much types of how one can protect oneself from unwanted pregnancy while enjoying this very sex. (But not to protect from sexually transmitted diseases! Don’t forget.) All these types are different in effectiveness, in action that is required from its users and in side effects.

There are many types of contraception methods.

· Barriers methods of birth control (spermicides, male and female condom, contraceptive sponge, diaphragm, cervical cap and others)

· Intrauterine device (IUD)

· Fertility awareness method: periodic abstinence or natural family planning (calendar rhythm method, basal body temperature method, mucus inspection method, withdrawal method, lactational infertility, sympotothermal method, ovulation indicator testing kits, douching and urination, some others)

· Permanent methods of contraception (vasectomy, tubal ligation, hysterectomy, STOP – selective tubal occlusion procedure)

· Hormonal contraception

There is also emergency contraception method (in some emergency unexpected occasions): emergency hormonal contraception and emergency IUD.

What is hormonal contraception?

Hormonal contraception is one of the methods of contraception that act on the hormonal system. Hormonal contraceptivesmay be introduced into the body (mainly woman’s, but currently there are some contraceptives designed for men) in many different ways: orally (the first method in the list), vaginally, transdermally, or through injections or implants.

Hormonal contraceptives are extremely popular as they are easy in usage and very effective. These types of contraceptives must be prescribed by a health care provider, as your personal family history should be considered and other related things. Other reason why thousands of women prefer this method of contraception is because they are reversible. You stop taking them and can easily get pregnant if you want (or choose another method).

For better understanding the mechanism of action of the hormonal method let’s start from the very beginning.

What our periods come from?

Everything starts in the brain when hypothalamus produces the hormone that is called gonadotropinreleasing, or shortly GnRH. This hormone in its turn triggers the pituitary gland to release the follicle stimulating hormone (or FSH). Through the bloodstream this FS hormone travels right into the woman’s ovaries and initiates the growth of a follicle.

The follicle starts to develop and generates estrogen, the levels of which reach the high numbers in 13th day (approximately, in a standard 28 day cycle). This peak provokes the luteinizing hormone come from the luteinizing hormone to the ovarian follicle. About 36 hours later, a mature egg is released into the fallopian tube from the corpus luteum (the empty follicle). The cells of this empty follicle begin to produce progesterone and estroge and the womb (uterus walls) begins preparing to accept the fertilized egg (its walls thicken with blood). Then the empty follicle begins to diminish – no production of the hormones – no hormonal support for the ready womb - the uterine lining begins to shed off. The woman’s monthly menstrual period begins as the ‘material’ for the fertilized egg (that hasn’t come) is unnecessary any more. Low levels of estrogen and progesterone also signal the hypothalamus to start the process in the brain over again.

What types of hormonal birth control method are available ‘on the shelves’?

The hormones can be estrogen or progesterone, or both of them. Mind that none of the hormonal methods of birth control protect a woman against sexually transmitted infections (STD).

Hormonal methods use two basic formulas:

1.  Combination hormonal methods

These methods contain both hormones – estrogen and progestin (synthetic progesterone)

· Birth control pills – pills that are taken by mouth and are effective as long as you use them. You take it daily for three weeks and then stop taking them and have your periods

· Skin patches (the Ortho Evra Patch) - is an adhesive patch that releases estrogen and progestin through your skin for 7 days (you can take in on your abdomen, buttocks, or upper arm). You use one patcheach week for 3 weeks, then no patch for 1 week (during which you have your periods)

· Rings (the Nuva Ring) – is a small flexible vaginal ring. You insert the vaginal ring at home and leave it in place for 3 weeks. This gives you continuous birth control for the month (releases a continuous low dose of hormones into the vagina to prevent pregnancy). On the first day of the fourth week, you remove the ring and you have a menstrual period.

2.  Progestin-only hormonal methods

These methods contain only hormone progestin

· Mini-pill or progestin-only pill (POP) – pills that are taken by mouth. You take them every day without a pause

·  Shots (Depo Provera Shot/Injection) - slowly releases the synthetic form of progesterone medroxyprogesterone acetate and protects against pregnancy for a period of 11 to 14 weeks

·  Mirena IUD  - releases a low amount of progestin continuously over a 5-year period as a way to prevent pregnancy

·  Implants (Norplant, Norplant-2) – contain levonorgestrel (a progestin), implanted subdermally in the upper arm and effective for five years

How do hormonal methods work?

All hormonal contraceptives have at least three mechanisms of action.

·  Hormonal contraceptives prevent ovulation.

This is a major mechanism of hormonal birth control. As there is no ovulation there is no egg that should be prevented from fertilization.

·  Hormonal contraceptives prevent fertilization.

As any woman can ovulate at some risky point there is another way to prevent pregnancy. The main principle is that the natural secretions in the vagina change their consistency, thus making it very hard (or impossible) for the sperm to get to the egg for fertilization.

·  Hormonal contraceptives prevent implantation.

As things happen, the sperm may still reach the egg. The egg is fertilized. But hormonal methods make one extra step toward birth control issue. They make it difficult for the fertilized egg to implant in the uterus by keeping the edometrium (lining of the uterus) thinned. This leads to the death and the expulsion of the embryo. Some patients and doctors consider this point to be ‘abortive’ and do not accept these methods of contraception as most scientists agree this sometimes occur (no one knows how often).

Hormonal contraceptives may contain two or only one hormone. Progestin together with estrogen gives more effectiveness. And these contraceptives work on three stages. But the the estrogen component is responsible for most of the serious health problems associated with hormonal methods. Progestin-only methods are much safer, give less side effects, but mainly working on ‘preventing fertilization’ and ‘preventing implantation’ principles. Only some new types of progestin-only pill can cope with the three principles.   

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While using hormonal methods of contraception you are likely to have some very light or skipped periods and sometimes bleeding between the periods (which will pass in 3-4 months). Skin patch may cause skin irritation at the site and vaginal ring may – vaginal discharge and irritation of the vagina. These are the mild side effects of the methods.

Though these methods do not protect you from STD they are the most effective (of course after the permanent methods, that give 0,15 in men and 0,5 failure percentage). The rate of failure with combined pills is 2-5%, in POP – 5%. Implant rate of failure is 0,05, that is actually even higher than with sterilization.

Valentyna Ant.


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