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Hormonal Contraceptives

For medical students2 min readUpdated 2026-10-10

Hormonal contraceptives are specialized pharmacological agents widely used for family planning and the reliable prevention of unwanted pregnancy. Their high efficacy is due to a comprehensive impact on the reproductive system: the drugs not only suppress ovulation at the central nervous system level but also create insurmountable physiological barriers to fertilization and subsequent peripheral implantation.

Primary estrogen*Ethinyl estradiol* is most commonly used as the estrogenic component in these formulations.

Basis of effectThe dominant contraceptive action is always provided by the progestin component.

Dose restrictionTo reduce the risk of thrombosis, the estrogen content in pills does not exceed 35 mcg.

Types of COCsBased on hormone dose variations throughout the cycle, preparations are divided into monophasic, biphasic, and triphasic.

General Classification of Contraceptive Agents

In modern pharmacology, pregnancy prevention agents are divided into several main groups. The basic classification of hormonal contraceptives includes the following categories:

Combined estrogen-progestin contraceptives (COCs) — the main and most extensive group on which most family planning regimens are based.
Progestin-only pills (POPs) — also known in medical practice as mini-pills.
Emergency contraceptives — a specific group of postcoital drugs used after unprotected intercourse.

Composition and Safety of Combined Preparations

Classical combined oral contraceptives consist of two active substances. The estrogenic component in the vast majority of cases is represented by ethinyl estradiol. Various synthetic progesterone analogs act as the progestin component.

It is important to understand the interaction of these components. The dominant contraceptive effect is always provided specifically by the progestin component. The role of estrogens is that they potentiate (significantly enhance) the inhibitory effect of progestins on the secretion of pituitary gonadotropins.

However, the presence of estrogens requires strict safety monitoring. Systematic intake of estrogens stimulates the synthesis of procoagulants (blood clotting factors) in the liver, which directly increases the risk of thrombosis. To minimize the probability of thromboembolic complications, pharmacologists limit the dosage: in modern pills, the estrogen content typically does not exceed 35 mcg.

Depending on the variation of hormone doses throughout the menstrual cycle, COCs are divided into 3 types: monophasic (with a constant dose of both components), biphasic, and triphasic.

Mechanism of Contraceptive Action

The action of combined preparations is implemented simultaneously at two levels: central and peripheral.

1. Central Action (Suppression of Ovulation) Mediated through effects on the pituitary gland:

Estrogen effect: acting via negative feedback, they suppress follicle-stimulating hormone (FSH) production during the proliferative phase of the cycle. As a result, the growth and maturation of ovarian follicles are slowed.
Progestin effect: they purposefully inhibit the release of pituitary luteinizing hormone (LH). The net result of this combined action is the complete blockade of ovulation.

2. Peripheral Action (Progestic Effects) Even if ovulation occurs, additional protection is triggered at the target organ level:

Cervical factor: under the influence of the drugs, the cervical glands produce very thick and viscous mucus. This creates a reliable mechanical barrier preventing sperm penetration into the uterine cavity.
Tubal factor: there is a pronounced decrease in fallopian tube peristalsis. This causes impaired egg transport — it reaches the uterus untimely, making fertilization impossible.
Uterine factor: the drugs cause profound structural changes in the endometrium. As a result, implantation of an already fertilized egg is made impossible. This mechanism is classified as abortifacient and is also used in medicine for pregnancy termination.

Mnemonic

Remember the central mechanism of COCs easily with associations: Estrogens — FSH (slow follicle growth), Progestins — LH (block ovulation). Peripheral progestin action follows the rule of three barriers: thick mucus (cervix), weak peristalsis (tubes), unsuitable endometrium (uterus).

Frequently asked questions

What specific synthetic progestins are included in modern COCs?

Modern combined oral contraceptives contain synthetic progestins, including:

Norgestimate.
Desogestrel.
Gestodene.
Dienogest — possesses antiandrogenic activity.
Drospirenone — possesses antimineralocorticoid activity.
Cyproterone — possesses antiandrogenic activity, used for example in Diane-35.
Levonorgestrel — a 19-nortestosterone derivative used in COCs.

What active substances are used as emergency postcoital contraceptives?

Five groups of agents are used for emergency hormonal contraception:

Estrogens.
Combined estrogen-progestin preparations (ethinyl estradiol and levonorgestrel).
Progestins.
Danazol.
Mifepristone — a synthetic progesterone antagonist; used for emergency postcoital contraception as a single 600 mg dose within 72 hours after intercourse.

What are the absolute contraindications to prescribing COCs?

Contraindications to combined oral contraceptives include various pathological and physiological states. These include:

Pregnancy — an absolute contraindication to hormone therapy.
Severe hepatic impairment — limits the use of steroids.
Thrombophilias — states with a high risk of thrombosis.
Smoking — sharply increases the risk of thromboembolism when taking these drugs.

Which drugs belong to the progestin-only pill (mini-pill) group?

Oral progestin-only contraceptives contain microdoses of synthetic progestins. These include:

Demulen — contains ethynodiol 0.5 mg.
Microlut — contains levonorgestrel 0.03 mg.
Exluton — contains lynestrenol 0.5 mg.
Cerazette — contains desogestrel 0.075 mg.

What side effects are typical for the estrogen component of COCs besides the risk of thrombosis?

Aside from thrombosis risk, the estrogen component of combined oral contraceptives can cause other adverse effects, including:

Sodium and water retention — leading to edema.
Hypertension — caused by the stimulating effect of estrogens on the renin-angiotensin-aldosterone system.
Carbohydrate metabolism disorders — manifested by decreased glucose tolerance and elevated blood glucose, which may trigger latent forms of diabetes mellitus.

Which COC component is responsible for the primary contraceptive effect?

The dominant contraceptive action is provided by the progestin component. Estrogens act as synergists, potentiating the inhibitory effect of progestins on pituitary gonadotropin secretion.

Why is the estrogen dose strictly limited in modern COCs?

Systematic estrogen intake stimulates the hepatic synthesis of procoagulants. Limiting the dose to 35 mcg is necessary to reduce the risk of thrombosis and thromboembolic complications.

How do progestins prevent sperm penetration?

They act on the cervical glands, inducing them to produce very thick and viscous mucus. This creates a reliable mechanical barrier against sperm progression.

What is the uterine factor in contraceptive action?

Under the influence of the drugs, structural changes occur in the endometrium, making the implantation of a fertilized egg impossible. This same abortifacient mechanism is used to terminate pregnancy.

Go deeper

Characteristics and clinical use of progestin-only pills (mini-pills).
Mechanism of action of emergency (postcoital) contraceptives.
Differences in dosing regimens for monophasic, biphasic, and triphasic COCs.
Synthetic progestins: types and pharmacological profiles.
Abortifacient mechanism of contraceptive action at the endometrial level.