What Role Does the Thyroid Play in Your Body and Your Weight?

Here’s how your thyroid, and the hormones it releases, impacts your health and your waistline.

Think of the thyroid as the personal assistant to your major organs and bodily functions. It helps everything from your brain to your heart to your muscles do their jobs. And you need this gland to produce hormones that allow you to perform at your best. To get a fuller picture of the health duties of the thyroid hormone, let’s take a deeper dive into the role it plays in the body. 

The Role of the Thyroid and the Thyroid Hormone in the Body

The thyroid gland typically forms the shape of a butterfly and sits in the lower front of the neck, below the Adam’s apple. It takes in iodine (from foods) and combines it with the amino acid tyrosine. From there, it makes two thyroid hormones known as thyroxine (or T4) and triiodothyronine (or T3). The thyroid then releases these hormones into the blood where they float to every tissue in your body to help convert oxygen and calories into energy. That means your thyroid can affect processes like how your body burns calories and how fast your heart beats, as well as how your body stays warm and how well your muscles work. In other words, the thyroid’s work as an assistant is pretty crucial for a healthy body.

In true team-oriented fashion, the brain also helps out the thyroid. It tells this gland when to make more or less of T4 and T3. The pituitary gland—located at the base of the brain—produces thyroid stimulating hormone (or TSH), when it notices that your T4 and T3 levels drop. After T4 and T3 rises in the blood, then the pituitary gland will pull back on making TSH. Clear communication between the thyroid and pituitary gland help with metabolism and daily function. 

Why It’s Important to Know Your TSH Level

To test how well your thyroid functions, your docs will probably look at a blood sample to measure the thyroid stimulating hormone. Changes to your TSH often signals whether your thyroid makes enough T4 and T3. If you’re low on TSH, you might have a condition called hypothyroidism. If you have a high amount of TSH, you might have a condition called hyperthyroidism. Otherwise, normal TSH levels are indicative of a normal functioning thyroid1

There are a few symptoms that could alert you to hyper- or hypothyroidism. For example, if you experience fatigue or muscle weakness, a rapid or irregular heart beat, frequent bowel movements, mood wings, or weight loss, it’s time to mention it to your doctor as these are signs of hyperthyroidism2. If you experience weight gain, joint or muscle pain, constipation, heavy periods, or a slow heart rate, it could mean you have hypothyroidism and your symptoms should be discussed at your next medical visit3

Getting a blood test to look at your thyroid stimulating hormone and whether you have overactive or underactive thyroid is crucial for a few reasons. Untreated, both hyper- and hypothyroidism could lead to other serious health problems. For example, hyperthyroidism may lead to an irregular heartbeat that then causes heart disease, stroke, or blood clots2. Eye disease and osteoporosis can also come up as a result of hyperthyroidism. On the other hand, hypothyroidism might lead to high cholesterol. It can also cause the body to slow to the point that it shuts down—but only in super severe cases3

The Relationship Between Thyroid Hormone and Your Weight

If we were to put a label on the relationship between your thyroid hormone and the number on your scale it would get “complicated.” In general, because your thyroid hormone regulates metabolism, it can affect your weight. Experts believe this effect comes from the link between the thyroid hormone and your basal metabolic rate (or BMR). BMR refers to the amount of oxygen your body uses at rest. This can influence the number of calories your body burns.

People with a thyroid gland that doesn’t produce enough hormone (aka underactive thyroid) tend to have a low basal metabolic rate. Those with an overactive thyroid tend to have high basal metabolic rates4. This often translates to weight gain for those with an underactive thyroid and weight loss for those with an overactive thyroid. Research is also looking at the link between the thyroid hormone and obesity, body mass index, and waist circumference(5)(6)

Because the thyroid aids in the body’s main functions, from your metabolism to your heart rate, it’s crucial to talk to your doctor about it. You want to make sure it’s working right, plus find out from your healthcare provider how you can keep it that way. 

If you want to find out your thyroid stimulating hormone level, check out our SoWell Health Weight Biology Kit, which reveals other key info about your health too. 

1. American Thyroid Association. “Thyroid Function Tests.”

2. National Institute of Diabetes and Digestive and Kidney Diseases. “Hyperthyroidism (Overactive Thyroid).

3. National Institute of Diabetes and Digestive and Kidney Diseases. “Hypothyroidism (Underactive Thyroid).”

4. American Thyroid Association. “Thyroid and Weight FAQs.”

5. Thyroid. Association of Serum Thyrotropin 

with Anthropometric Markers of Obesity in the General Population. September 2016. 

6. Indian Journal of Endocrinology and Metabolism. Hypothyroidism and obesity: An intriguing link. July/August 2016. 

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