Do you sometimes feel like your body is just not functioning properly, or that you are very tired? Or do you sometimes feel like your body is racing ahead of your mind, and you feel very anxious? One reason for these things could be a very small, but very important thing in your body. That is the thyroid hormone. Today, let's talk about what this thyroid hormone is, what it does to our body, and what problems come with its fluctuations.
What is Thyroid Hormone? Simply put...
Think of your body as a big machine. The thyroid hormone is a key switch that controls the speed at which this machine works, that is, the metabolic rate . This hormone is essential for the development of a small baby's brain.
Do you know who makes this hormone? It's a small butterfly-shaped gland under the skin at the front of your neck. We call it the thyroid gland . It's part of our body's endocrine system .
Hormones are like messengers running through our bodies. They travel through the blood and tell various organs, muscles, and other tissues what to do and when to do it.
Now we're talking about metabolism . Simply put, it's the complex process that turns the food we eat into energy. Every cell in our body needs energy to function.
Actually, when we say "thyroid hormone", we are talking about two main hormones. They are thyroxine (Thyroxine - T4) and triiodothyronine (Triiodothyronine - T3) . We often call these two together "thyroid hormone". Do you know what? The hormone T4 is usually not very active, which means it does not have much effect on cells. But the hormone T3 is the most active. When T4 is released from the thyroid gland, some organs in our body convert it into T3. Only then can it affect cells and our metabolism.
Another thing, the thyroid gland also secretes a hormone called calcitonin . It controls and lowers the calcium level in the blood. However, calcitonin is not included in the name "thyroid hormone", and it does not affect our body's metabolism like T3 and T4.
How are these thyroid hormone levels controlled? It's a very amazing mechanism!
The production and secretion of these T4 and T3 hormones is controlled in a very complex, but very beautiful way. We call it a feedback loop system . This involves:
- Hypothalamus : This is located in your brain. It controls things like blood pressure, heart rate, body temperature, and digestion.
- Pituitary gland : This is also a small gland located under the brain, below the hypothalamus. It is about the size of a pea. It produces and secretes about eight types of hormones.
- Thyroid gland : The butterfly we talked about earlier.
- A few more hormones.
Imagine this is like working in a big company.
1. First, the hypothalamus (like a big manager) in the brain releases a hormone called Thyroid-Releasing Hormone (TRH) that stimulates the release of thyroid-stimulating hormone .
2. This TRH goes to the pituitary gland (like an assistant manager) and tells it to make and release thyroid-stimulating hormone (TSH) .
3. Then this TSH goes to the thyroid gland (like a worker) and tells it to make T4 and T3. About 80% of the hormones made in this way are T4, and the other 20% are T3. To make these T4 and T3, the thyroid gland also needs a nutrient called iodine . We get it from the food we eat.
Now this chain of hormones is controlled by what is called a ``feedback loop'' . That is, when the levels of T3 and T4 in the blood increase, it goes to the hypothalamus and pituitary and says, "Okay, enough, stop making TRH and TSH." When the levels of T3 and T4 decrease, this process starts again. This is how we can keep the thyroid hormone levels in our body at a certain level.
Think of it like the AC in your house. When the room gets colder, the AC turns off, and when the room gets hotter, it turns on.
However, if there is a problem with the hypothalamus, pituitary gland, or thyroid gland, the balance of hormones including T3 and T4 can be disrupted.
What do thyroid hormones do to our bodies? Or, their role!
After T4 is released into the blood from the thyroid gland, some cells in our body convert it into T3. This process is called de-iodination (removal of iodine). This is because the cells that are affected by thyroid hormones can use T3 better than T4. That is why we consider T4 to be the inactive hormone and T3 to be the active hormone.
The tissues, glands, organs, and systems that can convert T4 into T3 are:
- Liver
- Kidneys
- Muscles
- Thyroid gland `(Thyroid)`
- Pituitary gland
- Brown adipose tissue (this fatty tissue helps maintain body temperature in cold conditions)
- Central nervous system
So, these T3 and T4 hormones affect every cell and organ in our body. How do they affect it?
- Your body controls the rate at which it uses calories (energy). This is called your metabolic rate . This affects whether you lose or gain weight. Some people say that no matter how much they eat, they don't gain weight, while others say that they gain weight even when they eat a little. This could be one reason.
- Your heart rate slows down and increases.
- It lowers and raises body temperature. Some people just feel cold, while others just feel like they're sweating.
- It affects the speed at which food moves through the digestive system.
- Affects brain development (especially in childhood).
- Controls how muscles contract.
- It maintains skin and bones. That is, it controls the rate at which new cells are produced to replace dead cells (this is normal).
What tests are done to check thyroid levels?
There are several blood tests that can be done to check your thyroid levels and see if your thyroid gland is working properly. These are commonly called thyroid function tests . The main ones are:
- Total T4 test `(Total T4 test)`
- Free T4 (FT4) test
- Total T3 test `(Total T3 test)`
- Free T3 (Ft3) test
- Thyroid stimulating hormone test `(TSH test)`
Your doctor may also order other tests, for example:
- Thyroid antibodies : These help diagnose various autoimmune thyroid conditions.
- Thyroglobulin : This test is used to diagnose thyroiditis and monitor treatment for thyroid cancer.
What diseases occur if thyroid hormones are abnormal?
There are several conditions that are caused by, or contribute to, abnormal levels of thyroid hormones. Thyroid disease is very common. It is said that women are five to eight times more likely to develop thyroid disease than men .
The main thyroid conditions are:
- Hypothyroidism (underactive thyroid) : This is when the body doesn't produce enough thyroid hormones. Everything in the body starts to function slowly.
- Hashimoto's disease : This is an autoimmune condition. This means that our body's own immune system attacks the thyroid gland. This causes hypothyroidism.
- Hyperthyroidism (overactive thyroid gland) : This is when the thyroid gland produces too much thyroid hormone, causing everything in the body to work too fast.
- Graves' disease : This is also an autoimmune condition that causes hyperthyroidism.
- Thyroiditis (inflammation/swelling of the thyroid gland) .
- Thyroid nodules .
- Goiter (enlargement of the thyroid gland/swelling in the neck) .
- Thyroid cancer .
Remember when we talked about the hypothalamus and pituitary gland? Problems with those glands can also cause thyroid hormone levels to fluctuate, because they help regulate thyroid hormones.
When should I see a doctor about thyroid hormones?
Often, when thyroid hormone levels are abnormal, it manifests itself in symptoms that we experience. Thyroid hormones control the speed of our body's metabolism. So, if thyroid hormones increase, the speed increases more than normal, and if they decrease , the speed decreases. These imbalances can cause symptoms such as:
- Weight gain or loss for no reason.
- Decreased or increased heart rate.
- Inability to tolerate cold or heat. (Even in a country like Sri Lanka, if you feel particularly cold/hotter than others.)
- Dry skin or increased moisture.
- Irregular menstrual cycles in women.
- Feeling very tired, or just feeling anxious.
- Conditions like constipation or diarrhea.
- Forgetfulness, difficulty keeping your mind in one place.
If you have these symptoms, it's best to see a doctor. They can do some simple blood tests to see if your thyroid hormone levels are out of whack.
Finally, a few things to remember (Take-Home Message)
Thyroid hormone is a very important hormone that affects many things in our body. Sometimes it can be too low or too high in our body. The good news is that many thyroid conditions can be successfully treated.
If you have symptoms related to thyroid hormones, or if you want to know if you have any risk factors for developing a thyroid condition, don't be afraid to talk to your doctor. They are there to help you. Taking care of your body and finding out if there is a problem early is the best way to live a healthy life.
` thyroid hormone, thyroid hormone, metabolism, hypothyroidism, hyperthyroidism, TSH, T3, T4
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