Can Birth Control Cause Thyroid Issues?

The thyroid gland is a butterfly-shaped organ located in the lower part of your neck. It sits a little below the Adam's apple (the laryngeal prominence) and above the collarbone (clavicle). This gland is part of the endocrine system and plays an essential role in women's health. It produces just the right amount of triiodothyronine (T3) and thyroxine (T4) hormones that are critical for: 

• Normal growth 
• Metabolism
• Energy production 
• Reproduction
• Temperature control
• Digestive function 
• Brain development

Hypothyroidism occurs when the thyroid is underactive and doesn't produce enough hormones. It affects 1 in 300 people in the United States and is most common among females and older adults. Alternatively, hyperthyroidism occurs when the thyroid is overactive and produces too many hormones.

This article reviews the link between birth control and hypothyroidism, including how birth control affects the thyroid and lab test results and what to expect when you go off birth control. 

How Does Birth Control Affect the Thyroid?

Hormonal birth control contains reproductive hormones, including estrogen, progesterone, or a combination of both, and comes in various forms including: 

• Oral contraceptives (hormonal birth control pills or OCPs)
• Shots
• Patches
• Hormonal intrauterine device (IUDs)
• Vaginal ring

Reproductive hormones, including estrogen, work closely with thyroid hormones. The estrogen in most hormonal birth control can alter how thyroid hormones are made, used, and converted. 

Estrogen increases thyroid-binding globulins (TBG), which prevents thyroid hormones from freely circulating in your blood. It can also influence iodine uptake. This is significant because iodine deficiency is the leading cause of hypothyroidism.

Research suggests that longtime use of hormonal birth control is strongly associated with hypothyroidism. This is especially true for those who have taken hormonal birth control for over 10 years. 

Your healthcare provider may still advise you to take hormonal birth control if you have hypothyroidism. However, they may want to increase your dose of thyroid medication and monitor you more closely. 

Drugs, including hormonal birth control, can affect how thyroid medication is absorbed and can decrease its effectiveness. This doesn't mean you can't take these medications, but it's important to provide your healthcare providers with a current medication list. This way, they can check for drug interactions, monitor you more closely, and adjust medications' dosages and timing as needed. 

Can Birth Control Alter Thyroid Test Results?

Healthcare providers diagnose and monitor hypothyroidism by symptoms and blood test results. These blood tests include thyroid-stimulating hormones (TSH), triiodothyronine (T3), and thyroxine (T4).

The pituitary gland produces the TSH that helps your thyroid gland release T3 and T4. When T3 and T4 levels are low, the pituitary makes more TSH. High levels of TSH and low levels of T4 often indicate hypothyroidism. 

The estrogen in hormonal birth control can affect thyroid test results even if you do not have a thyroid disorder. Estrogen can increase the T3 and T4 levels. However, the TSH typically stays within the normal range. 

Can Hypothyroidism Affect the Effectiveness of Birth Control?

While there is no evidence that abnormal thyroid function or thyroid medications affect the performance of birth control, it’s always best to speak to your healthcare provider about your specific situation.  

The best way to ensure oral birth control pills are 99% effective at suppressing ovulation is to take them consistently and correctly. When not taken consistently at the same time each day, the failure or pregnancy rate is about 4% to 7%. 

What to Expect When Going Off Birth Control 

Talk with your healthcare provider if you stop taking hormonal birth control. If you take thyroid medication, your provider may need to decrease your dose as the thyroid medication should work more efficiently once you're off hormones.

Your healthcare provider will also want to monitor your TSH blood levels regularly to ensure you get the correct thyroid medication dose. 

Otherwise, stopping birth control can be done safely at any time. You may notice some menstrual irregularities or spotting between periods. This is typically temporary and resolves within a few months. 

Remember that you can get pregnant as soon as you stop taking birth control. If you are not planning to get pregnant, use another form of birth control, such as condoms or a diaphragm. 

If you do become pregnant, notify your healthcare provider. They may want to adjust your thyroid medication dose and monitor thyroid levels to promote a healthy pregnancy.

Summary 

Hypothyroidism is a disorder where the thyroid doesn’t produce enough hormones. Estrogen, a hormone in most hormonal birth control, can alter how thyroid hormones are produced and work. Long-term use (over 10 years) of hormonal birth control increases your risk of hypothyroidism. 

Estrogen can also affect the T3 and T4 thyroid blood test results, even if you do not have a thyroid disorder. However, it does not typically affect TSH levels.

You can still take birth control if you have hypothyroidism. However, your healthcare provider may want to increase your dose of thyroid medication and monitor you more closely. Talk with your healthcare provider if you decide to stop taking hormonal birth control; they may want to decrease your dose.

A Word From Verywell

Many women take hormonal birth control at some point in their life. The thought of it leading to hypothyroidism can be concerning. Keep in mind that the risk is small and usually only results from long-term use. 

Talk with your healthcare provider if you are concerned about your specific situation. They can also discuss nonhormonal birth control options if that is best for you.