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When it comes to heart health, we’re used to talking about cholesterol, blood pressure, and lifestyle. But there’s one often-overlooked organ that deserves a seat at the table: your thyroid. This small, butterfly-shaped gland at the base of your neck plays a significant role in regulating metabolism and, in turn, your heart.
Both underactive (hypothyroidism) and overactive (hyperthyroidism) thyroid conditions can quietly disrupt cardiovascular function. The symptoms are easy to miss. The consequences? Not so much.
Let’s take a closer look at how the thyroid and heart are connected, and why paying attention to this gland could help protect your cardiovascular health.
Small Gland, Global Impact
The thyroid produces two main hormones: T3 (triiodothyronine) and T4 (thyroxine). These hormones influence everything from how fast your cells burn energy to how your heart contracts and pumps blood.
Thyroid hormones influence the heart in two main ways. One occurs inside cells, where hormones interact with DNA to control the production of specific heart-related proteins (genomic effects). The other occurs quickly outside the cell, where it affects how the heart muscle and blood vessels behave, changing factors such as heart rate, rhythm, and blood vessel tightness (non-genomic effects).
Put simply, whether you’re at rest or under stress, thyroid hormones help determine how your heart behaves.
Hypothyroidism: When the System Slows Down
Hypothyroidism is far more common than hyperthyroidism, especially among women and older adults.1 It occurs when your thyroid doesn’t produce enough hormone. The signs – fatigue, weight gain, constipation, cold intolerance – can be subtle and easily mistaken for normal aging or other conditions.
But beneath the surface, hypothyroidism may cause:1
- Slower heart rate (reduces blood flow)
- Stiffened arteries (increase blood pressure)
- Elevated cholesterol (risk of plaque build-up)
- Fluid retention (stresses the heart)
Muscle aches are also a common symptom and can sometimes be confused with statin-related side effects. Interestingly, people with statin intolerance are more likely to have undiagnosed hypothyroidism, and treating the thyroid issue may resolve muscle symptoms.3
Left untreated, hypothyroidism can contribute to:
- Heart failure
- High blood pressure
- Coronary artery disease
- Stroke
Even subclinical hypothyroidism, where hormone levels are just slightly off, has been associated with a higher risk of vascular problems and a progression to more serious disease.4
Hyperthyroidism: When the System Can’t Catch a Break
An overactive thyroid, or hyperthyroidism, causes the body’s systems to function at an abnormally high rate. The result? A heart that beats harder, faster, and sometimes irregularly.
Classic symptoms of a hyperactive thyroid include a rapid or irregular heartbeat (arrhythmia), palpitations, weight loss despite a normal appetite, excessive sweating or heat intolerance, and nervousness or irritability.
From a cardiovascular standpoint, hyperthyroidism can cause:4
- Atrial fibrillation (a common arrhythmia that increases stroke risk)
- High blood pressure
- Chest pain (angina), especially in people with narrowed arteries
- Heart failure (in cases of long-term strain)
Hyperthyroidism is relatively rare, affecting less than 1% of people in areas where iodine intake is sufficient (like most developed countries). But an overactive thyroid doesn’t always come with obvious symptoms or test results that scream “problem.” Even milder or early-stage forms, where symptoms may be minimal and hormone levels still appear normal, can cause cardiovascular damage, according to some researchers.4
The Cardiovascular Domino Effect
Here’s how thyroid dysfunction creates a ripple effect in the cardiovascular system:
- Metabolism shifts increase or decrease oxygen demand
- Changes in heart contractility alter how efficiently blood is pumped
- Vascular resistance shifts affect blood pressure and flow
- Electrophysiological activity changes create arrhythmia risks
- Lipid metabolism disruption raises cholesterol and increases the risk of plaque build-up in the vessels
Thyroid hormones even regulate the renin-angiotensin-aldosterone system (a hormonal system that controls blood pressure and fluid balance), and affect nitric oxide (NO) production, a key molecule in keeping blood vessels relaxed.4
One of the trickiest aspects of thyroid conditions is that they can creep up gradually and without obvious signs. Many people do not realize they have a thyroid problem until blood tests reveal abnormal hormone levels. Depending on symptoms, doctors may order further tests to get a complete picture. Unfortunately, routine thyroid screening is not the norm for people without symptoms. Furthermore, normal ranges can be abnormal for some individuals, which complicates the diagnosis and treatment.
A Healthy Partnership
When discussing heart health, it’s helpful to broaden our perspective. We often attribute thyroid issues to problems within the endocrine system, such as metabolic or hormonal imbalances. But our body’s systems don’t operate in isolation. Each part depends on the others for healthy functioning, just as the thyroid’s partnership with the heart influences the rhythm, force, and flow of cardiovascular function.
If you or a loved one is dealing with heart symptoms that seem vague, persistent, or out of proportion, consider this: the problem might be hormonal. And the fix might be more straightforward than you think.
The team at Nevada Cardiology Associates is here to help you connect the dots and improve your heart health. Reach out today to schedule a consultation and take the first step toward a healthier heart and body.
Note: If you experience a sudden onset of symptoms that appear to involve the chest or heart, seek immediate medical attention at your nearest emergency room or call 911 without delay..
References
- Harvard Health Publishing, Harvard Medical School. (2023, August 8). Thyroid hormone: How it affects your heart. Harvard Health; Harvard Health Publishing. https://www.health.harvard.edu/heart-health/thyroid-hormone-how-it-affects-your-heart.
- Precker, M. (2022, January 20). A healthy thyroid can play a crucial role in maintaining a healthy heart. Www.heart.org; American Heart Association. https://www.heart.org/en/news/2022/01/20/a-healthy-thyroid-can-be-key-to-a-healthy-heart.
- Harvard Health Publishing, Harvard Medical School. (2023, August 8). Thyroid hormone: How it affects your heart. Harvard Health; Harvard Health Publishing. https://www.health.harvard.edu/heart-health/thyroid-hormone-how-it-affects-your-heart.
- Soetedjo, N. N. M., Agustini, D., & Permana, H. (2024). The impact of thyroid disorder on cardiovascular disease: Unraveling the connection and implications for patient care. IJC Heart & Vasculature, 55. https://doi.org/10.1016/j.ijcha.2024.101536.
