Birth Control and Your Thyroid Health

Birth Control and Your Thyroid Health

birth control and your thyroid health
©️ Reproductive Health Supplies Coalition on Unsplash
Dr. Minako Abe
Medically reviewed by

Dr. Minako Abe, M.D., Board-certified emergency medicine physician researching the relationship between lifestyle and disease onset in relation to the immune system and cancer, Japan

Birth Control and Your Thyroid Health

Birth control or contraceptives are the different methods of reducing the chance of or preventing pregnancy. These methods have evolved in safety, effectiveness, and availability over the years. Modern birth control includes a range of options such as intrauterine contraception (IUD), hormonal methods, barrier methods, emergency contraception, and permanent contraception. 


Intrauterine Devices (IUD)

An IUD is a contraceptive device that often comes in a T-shape, and is inserted into the uterus. IUDs are very effective and reversible forms of birth control that are for long-term use. There are two forms of intrauterine contraception: levonorgestrel intrauterine system (LNG IUD) and copper T intrauterine device (IUD).

LNG-IUD is often combined with estrogen as part of hormone replacement treatment. The device is small, plastic, and T-shaped and is inserted into the uterus by your healthcare professional. LNG-IUDs work similarly to levonorgestrel implants or pills, but the IUD version releases much lower doses of levonorgestrel hormone at a regulated rate. 

Levonorgestrel thickens the mucus that lines the cervix and prevents the endometrial lining from proliferating to prepare for egg implantation in the uterus. After ovulation, the endometrium is an attachment site and provides nutrients for a potential embryo. 

By thinning the lining of the uterus, levonorgestrel effectively prevents fertilization and implantation of an egg, while also creating an unsuitable environment for sperm. With a thick mucus lining, sperm motility, the ability to move, is inhibited and the sperm cannot reach enter the uterus.

The LNG IUD is over 99% effective at preventing unintended pregnancy. LNG-IUDs also have non-contraceptive benefits such as treating gynecological disorders such as menorrhagia (heavy bleeding), dysmenorrhea, anemia, and pain caused by endometriosis

It should be noted that LNG-IUDs cannot prevent sexually transmitted infections such as HIV, therefore, an LND-IUD needs to be used in addition to condoms and/or other protective barrier methods.  Depending on the type of LNG-IUD, they can last between 3 to 8 years, and have a failure rate of 0.1-0.4%.

Hormonal Methods

Hormonal contraceptives are some of the most popular forms of birth control, especially the birth control pill. This contraceptive changes an individual’s hormone levels to prevent a mature egg from being released by the ovaries into the uterus during ovulation. Some also prevent the egg from implanting in the womb. Others make the mucus lining of the uterus thicker to prevent sperm from reaching the egg. Hormonal methods can be impacted by other medications such as antibiotics, blood pressure medication, and antifungal products. 

Side Effects:

  • Headaches
  • Nausea
  • Sore breasts
  • Vaginal yeast infections
  • Thrombosis (blood clots)

Hormonal contraceptives are also used to relieve period pain and improve skin by reducing acne. Hormonal contraceptives can be administered orally, injected, transdermal (through the skin), transvaginal (through the vagina), and intrauterine (in the uterus).

Types of Hormonal Contraceptives:

1. Birth Control Pill

They contain a combination of estrogen and progesterone hormones that are taken at the same time every day. Estrogen helps control menstrual bleeding, while progesterone prevents pregnancy. There are three types of birth control pills: combined estrogen-progesterone, progesterone-only, and continuous-use pills. It was estimated that in the United States, approximately 25% of contraceptive users preferred the birth control pill. The typical failure rate is 7%

2. Contraceptive Skin Patch

Depending on the brand, the typical contraceptive skin patch contains 0.6 mg of ethinylestradiol (EE) and 6.0 mg of norelgestromin (NGMN). EE is the estrogen hormone needed for menstrual bleeding, while NGMN mimics progesterone, the pregnancy-prevention hormone. The patch is worn on the upper body, lower abdomen, or buttocks to directly release estrogen and progesterone into the bloodstream. The typical failure rate is 7%.

3. Hormonal Contraceptive Vaginal Ring

The contraceptive ring is typically implanted in the vagina for 3 weeks and removed for one week to allow for menstruation before being replaced. It is a soft, flexible ring that is 4 mm thick and 54 mm in diameter. The ring releases progesterone and estrogen that are absorbed by the vaginal epithelium lining. 

This method avoids any hormones being absorbed by the gastrointestinal system, but it does not produce the same level of hormones as a combined estrogen-progesterone birth control pill. There are also concerns about leukorrhea, vaginal discomfort, and vaginitis. The typical failure rate is 7%.

4. Hormonal Birth Control Implant

Progesterone-only implants have a similar advantage to an IUD which is long-acting and reversible. The implant reduces the amount of luteinizing hormone and follicle-stimulating hormone in the blood.

Luteinizing hormone helps trigger the release of an egg from the ovaries while follicle-stimulating hormone is needed to grow ovarian follicles that will then release estrogen and progesterone. By preventing both hormones, ovulation is suppressed. The typical failure rate is 0.1%.

5. Injectable Contraceptive

These contraceptives contain hormones such as progesterone to prevent ovulation and thicken cervical mucus, which makes it difficult for sperm to reach the egg. They are highly effective and have a success rate of around 96%. Unlike birth control pills, they only need to be administered every 1 to 3 months and have a long-lasting effect.

However, like all forms of birth control, injectable contraceptives can cause the user to experience irregular bleeding or unusual changes in their menstrual cycle. There is also a possibility of reduced bone mineral density in individuals over 40 who plan on using injectable contraceptives for longer than two years.

Two progesterone-only injectable contraceptives exist: Depot medroxyprogesterone acetate (DMPA) and norethisterone-enanthate (NET-EN). The typical failure rate is 4%.

The Effects of Birth Control on Thyroid Health: How Does it Affect the Thyroid Gland?

Hormonal birth control uses synthetic versions of estrogen and progesterone to prevent ovulation, egg implantation, or sperm mobility; however, these synthetic hormones can affect the function of the thyroid gland which produces hormones to regulate metabolism in the body.

The thyroid gland releases two iodine-containing hormones called thyroxine (T4) and triiodothyronine (T3). The production of these hormones is managed by thyroid-stimulating hormone (TSH). T4 and T3 circulate in the bloodstream with thyroxine-binding globulin (TBG), a plasma protein made by the liver, binding to them. T4 and T3 are also sometimes bound to other plasma proteins such as transthyretin (TTR) and albumin.

Studies find that contraceptives that use estrogens and/or progesterones can influence the concentration of thyroid hormone-binding proteins in the blood. Estrogen can increase the concentration of TBG in the bloodstream within 2 weeks of use. This means that those with hypothyroidism, where the body is not making enough thyroid hormones, will require a higher dose of T4 treatment to maintain normal TSH levels and compensate for the decreasing amount of unbound thyroid hormones in the blood.

One study even found that females with a long history of taking birth control pills had a higher prevalence of hypothyroidism. Non-hormonal methods like barrier contraceptives (condoms) or copper IUDs are alternatives for those with hormone sensitivities, but anyone looking to start birth control who has been diagnosed with hypothyroidism should always consult their healthcare professional.

Before starting a new medication, they may need adjustments to their medication dosage or switch to a different type of contraception without the use of synthetic hormones. You should note that not all women who take birth control pills will experience these side effects. Hormonal imbalances can also be caused by genetic factors and other health conditions.

Alternatives to Hormonal Contraception

There are alternatives available for an individual who cannot take hormonal contraceptives due to thyroid conditions, breastfeeding individuals, and for convenience purposes.

Barrier Methods

The purpose of the barrier is to prevent the sperm and egg from making contact and for fertilization to occur.

1. Diaphragm or cervical cap

This is a vaginal barrier contraceptive by covering the cervix. The device blocks sperm and contains spermicide, a chemical that damages and kills the sperm before it can enter the uterus. 

A cervical cap is smaller than a diaphragm and lasts longer as it can be worn for up to 72 hours compared to a diaphragm which can be worn for up to 30 hours. Both methods are reversible and user-controlled, as in the individual inserts and removal of the device themselves.

Before using a diaphragm or cervical cap, you would need to get fitted by your doctor. The use of spermicide increases the risk of urinary tract infections (UTIs), and while maximum application times exist, the longer the device is used, the more risk there is of toxic shock syndrome. Moreover, neither device will protect against STIs. The typical use failure rate for the diaphragm is 17%.

Cervical Cap

  • Smaller
  • Maximum of 30 to 72 hours after insertion
  • 6 to 8 hours after intercourse
  • Covers the cervix with suction


  • Maximum of 24 to 30 hours after insertion
  • Forms a seal between the diaphragm and vaginal wall (not a complete seal)

2. Sponge

A sponge is made of polyurethane foam coated with spermicide. The sponge is inserted into the vagina up to 24 before intercourse and must stay in place for at least 6 hours afterward. It should never stay inside for longer than 30 hours total as it increases the risk of UTIs, vaginal infections, and toxic shock syndrome.

It does not protect against STIs and can cause some users to experience a burning feeling or allergic reaction. The typical use failure rate is 14% for women who have never had a baby and 27% for women who have had a baby (this is because childbirth can stretch the cervix and vagina and prevents the sponge from fully preventing sperm from reaching the cervix).

3. Copper IUD

Unlike LNG-IUDs that release progesterone, copper IUDs are T-shaped devices coated in copper. Copper is toxic to sperm. By releasing copper ions into the cervical and uterine  space, a cytotoxic inflammatory reaction occurs, and sperm are killed.

While rates of complication are low, copper IUDs can cause increased menstrual bleeding, pain, and infection right after insertion. A copper IUD can be used long-term for up to 10 years and can be used as an emergency contraceptive up to 5 days after intercourse. Like other female contraceptives, IUDs do not prevent STIs.The typical use failure rate is 0.8%.

Birth Control and Thyroid Medication

Like all medications, when taking thyroid medication always talk to your healthcare professional about what can be consumed before and after taking the medication. For example, you should take levothyroxine, a common thyroid hormone replacement medication, before a meal by between 30 minutes to 1 hour, and at least 3-4 hours after a meal.

Levothyroxine is recommended to be taken on an empty stomach to maximize how much of the medication is absorbed by the body. It is best to take your birth control separately from your thyroid medication, and always take the medication prescribed by your doctors.

ALWAYS listen to your healthcare professional when it comes to your medication.

Key Takeaways

  • Modern birth control includes a range of options such as intrauterine contraception (IUD), hormonal methods, barrier methods, emergency contraception, and permanent contraception. 
  • Hormonal birth control includes birth control pills, skin patches, contraceptive vaginal rings, birth control implants, and injectable contraceptives.
  • Hormonal birth control uses synthetic versions of estrogen and progesterone that can affect the function of the thyroid gland’s ability to regulate T4, T3, TSH, and TBG.
  • Estrogen can increase the concentration of TBG in the bloodstream which means that hypothyroid patients may require a higher dose of T4 treatment to maintain normal TSH levels and compensate for the reduced number of unbound thyroid hormones in the blood.
  • Alternatives to hormonal birth control include cervical caps, diaphragms, contraceptive sponges, and copper IUDs.


Birth control pills can impact thyroid function by affecting hormone levels in the body. Estrogen, a hormone present in many birth control pills, can influence the production and utilization of thyroid hormones, potentially leading to changes in thyroid function.

Certain types of birth control, such as those containing synthetic hormones like progestin-only pills or hormonal IUDs, may have less impact on thyroid function compared to combination birth control pills containing estrogen and progestin. However, individual responses can vary, and it’s essential to discuss contraceptive options with a healthcare provider.

Yes, some studies suggest that birth control pills containing estrogen may interfere with the absorption of thyroid medication, potentially reducing its effectiveness. It’s crucial for individuals taking thyroid medication and birth control to discuss these interactions with their healthcare provider to ensure proper management of thyroid health.


At ThyForLife, we do our utmost to provide accurate information. For detailed medical information regarding diagnosis, treatment, and general practices please consult your healthcare professional. Always listen to the advice of your healthcare provider.
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