How Do Estrogens/Progestins Work?

Reviewed on 1/6/2022

How do estrogens/progestins work?

Estrogens/progestins are combination hormonal medications used for contraception and in the treatment of uterine fibroids and other female hormonal disorders. Estrogens and progestins are synthetic formulations of the natural female sex hormones progesterone and estrogen and have similar effects.

Estrogens are a group of endogenous hormones responsible for the development and maintenance of the female reproductive system and secondary sexual characteristics. Progesterone is the other female sex hormone that prepares the endometrium, the inner lining of the uterus, for implantation and continuation of pregnancy.

Estrogens/progestins work by binding to estrogen and progesterone receptors, protein molecules in cells that respond to these hormones. Estrogens/progestins medications interfere with the functions of endogenous estrogen and progesterone to control excessive bleeding, prevent pregnancy, and relieve menopausal symptoms.

Estrogens/progestins formulations may contain different types of estrogens, progesterone, and other substances known as gonadotropin-releasing hormone (GnRH) antagonists that block the activity of GnRH produced by the hypothalamus. Some estrogen/progestin drugs may also contain iron to supplement iron loss from excessive bleeding.

Estrogens/progestins work in the following ways in the treatment of uterine fibroids:

  • GnRH antagonists bind to GnRH receptors in the pituitary gland and prevent GnRH from stimulating the release of the follicular stimulating hormone (FSH) and luteinizing hormone (LH). This reduces ovarian production of estrogen and progesterone, reducing the bleeding associated with fibroids.
  • The estrogen in the medication supplements the loss of natural circulating estrogen due to the medication and prevents bone loss due to reduced estrogen levels.
  • The progestin in the medication supplements the reduced progesterone level caused by the medication and protects the uterus from potential adverse effects from unopposed estrogen.

Estrogens/progestins work in the following ways in preventing pregnancy:

  • Suppress ovulation and maturation of the ovum by reducing the release of GnRH from the hypothalamus, and the release of FSH and LH from the pituitary gland.
  • Thicken the cervical mucus, hindering the passage of sperm into the uterus.
  • Thin the uterus lining (endometrium) preventing implantation of the fertilized egg.


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How are estrogens/progestins used?

Estrogens/progestins may be administered in the following ways:

  • Oral tablets or capsules are taken every day for the duration of treatment for uterine fibroids, not exceeding 24 months. The medication should be started as soon as possible, but no later than 7 days after the start of menstrual bleeding.
  • Oral tablets for contraception typically start on the first day of menstruation and are taken every day in varying cycles during the period birth control is followed.
  • Soft flexible rings are placed inside the vagina, which releases measured daily doses during the period contraception is practiced. The vaginal ring is left in place for 21 days with a gap of 7 days during which menstrual bleeding occurs, after which a new ring may be placed.

The uses of estrogens/progestins include:


Off-label uses:

What are the side effects of estrogens/progestins?

Side effects of estrogens/progestins may include the following:

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with travel medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.


Endometriosis occurs deep inside the uterus. See Answer

What are the names of estrogen/progestin drugs?

Generic and brand names of estrogen/progestin drugs include:


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