Can Hyperthyroidism Cause Hypertension?

Your thyroid may be small, but it has a big role to play in helping your body maintain normal functions.

When your thyroid works properly, other organs and systems can also work properly. 

On the other hand, when your thyroid doesn't work as it should by producing excessive or too few hormones, other systems in your body may be affected, including your cardiovascular system.

Hyperthyroidism can lead to a variety of heart complications, including high blood pressure. Here's what you should know about the relationship between hyperthyroidism and hypertension.

What does your thyroid do?

Your thyroid is a butterfly-shaped gland that is located at the front of your neck. It is responsible for producing thyroid hormones that are essential to the normal function of systems in your body, including your metabolism, heart rate, and body temperature.

The two main hormones that your thyroid produces are thyroxine (T4) and triiodothyronine (3). When your thyroid produces too much or not enough of these hormones, you may experience symptoms such as changes to your weight, sleep patterns, and energy levels.

What is hyperthyroidism?

Hyperthyroidism, also known as an overactive thyroid, is a condition that occurs when your thyroid gland produces too much T4 thyroid hormone, causing many functions in your body to effectively ‘speed up’.

It is estimated to occur in roughly 1 out of every 100 people over the age of 12 in the United States, and more commonly in females.

Hyperthyroidism is most commonly caused by Graves' disease (an autoimmune disease), but can also develop from too much iodine, overactive thyroid nodules, or for unknown reasons.

Symptoms of hyperthyroidism include:

• Irregular heartbeat

• Unexplained weight loss

• Increased appetite

• Insomnia

• Nervousness

• Sweating

Is high blood pressure a complication of hyperthyroidism?

Blood pressure refers to the pressure that your blood puts on your arteries as your heart beats.

Normal blood pressure is considered to be less than 120 (systolic pressure) over 80 (diastolic pressure) millimeters of mercury, or mmHg.

Hypertension, or high blood pressure, occurs when your blood pressure is higher than 120/80 mmHg. Both an underactive and overactive thyroid can lead to high blood pressure.

Around 1% of people diagnosed with hypertension have a thyroid disorder. When left untreated, an overactive thyroid can harm your heart.

Untreated hyperthyroidism can cause:

• Abnormal heart rhythms

• Chest pain

• Heart failure

• High blood pressure.

When a person has hyperthyroidism, their diastolic blood pressure(the second number) goes down as their blood vessels relax, while their systolic blood pressure (the first number) goes up. This is because the excess thyroid hormone causes the heart to contract harder, putting more strain on it.

How does hyperthyroidism affect your heart?

If you have untreated hyperthyroidism, the way that blood flows through your heart could be affected. This could also lead to several cardiovascular concerns, including hypertension and heart failure.

For instance, between 10-15%  of people with hyperthyroidism have atrial fibrillation,¹ which causes irregular heartbeats and palpitations. Likewise, individuals with hyperthyroidism have a higher risk of experiencing heart failure.

Finally, an estimated 20% of people with pulmonary hypertension (a condition causing excess pressure in the lungs) have thyroid disease, which is greater than the general population.

Therefore, it’s quite clear that there is a very strong connection between hyperthyroidism and heart problems.

What else could be causing your high blood pressure?

While hyperthyroidism can cause high blood pressure, many other underlying conditions can lead to a person developing hypertension. These include:

• Being overweight or obese

• Not exercising regularly

• Pregnancy

• Certain health conditions, such as diabetes

• Using tobacco

• Certain medications, such as birth control

• Stress

• Eating a diet that's high in sodium

High blood pressure often develops gradually over time and may not exhibit any signs or symptoms. Because of this, it's important to have your blood pressure checked at least once a year, and preferably more frequently if you fall into one or more of the above categories.

Identifying high blood pressure early can help make treating and managing it much easier and more effective.

The best way to manage high blood pressure is to treat its source. If your blood pressure is high due to an overactive thyroid, regulating your thyroid hormones should lead to your blood pressure lowering.

When to speak to a healthcare professional/endocrinologist

Both hyperthyroidism and hypertension can develop and progress with few or no symptoms.

Therefore, it's important to check in with your doctor to ensure that your blood pressure and thyroid levels are within normal range.

If you do notice one or more symptoms of an overactive thyroid, be proactive. Checking in with your doctor early can determine if you do have hyperthyroidism and identify the cause of your condition.

If necessary, your doctor can refer you to a thyroid specialist, also known as an endocrinologist. If your high blood pressure is, in fact, a result of an overactive thyroid, an endocrinologist can form a treatment plan that will aim to lower your blood pressure.

The lowdown

Your thyroid is a small gland that plays a big role in how the other systems and organs in your body work.

If your thyroid produces excessive thyroid hormones, also known as an overactive thyroid, many body organs can be affected, including your heart. This can lead to a range of cardiovascular concerns, such as high blood pressure.

If you experience any signs of hyperthyroidism, including losing weight unintentionally, insomnia, shaking, or nervousness, it's important to schedule an appointment with your doctor.

Once you're diagnosed, you and your doctor can work together to create a personalized treatment plan to manage your condition, as well as treat or prevent hypertension.