Does your thyroid seem a little overactive? Let's talk about Subclinical Hyperthyroidism!

Did your doctor say your TSH level is a little low in a recent blood test? Or are you having some strange, difficult-to-understand symptoms? You may have a condition called Subclinical Hyperthyroidism. Don't worry, it's usually not serious. Let's talk about this simply and clearly.

What is Subclinical Hyperthyroidism?

Simply put, `Subclinical Hyperthyroidism` is a condition where your thyroid gland is working slightly more than normal. But it is not as severe as `overt hyperthyroidism` .

The pituitary gland in our brain produces a hormone called `TSH` (Thyroid-Stimulating Hormone). This `TSH` tells the thyroid gland in our neck to make two hormones called thyroxine (`T4` - `thyroxine`) and triiodothyronine (`T3` - `triiodothyronine`). These `T3` ​​and `T4` hormones are what help our body's metabolism, that is, convert the food we eat into energy and use it for our body.

In `Subclinical Hyperthyroidism`, your blood `TSH` level is low, but your `T3` ​​and `T4` levels are normal. That means that the thyroid is a little overactive, so the pituitary gland says, "Okay, I don't need `TSH` right now, my thyroid is working fine," and it reduces the production of `TSH`. But the thyroid hormones (`T3`, `T4`) are not yet significantly elevated. That's what `subclinical` means - an underlying condition that doesn't show obvious symptoms.

This condition can sometimes be temporary , meaning it can get better on its own in a few days. However, for some people it can be permanent. Not everyone needs treatment.

Who is most likely to get this condition?

Anyone can develop `Subclinical Hyperthyroidism`, but the following people are at a slightly higher risk:

• People who are taking thyroid hormone replacement therapy (for example, levothyroxine) for hypothyroidism. Sometimes this can happen if the dose of the medication is slightly increased.
• For those over 65 years of age.

How common is this condition?

This is not a very common situation in countries like America.

About 0.7% of the population has `Subclinical Hyperthyroidism`, where TSH levels are less than 0.1 mIU/L. Another 1.8% have `TSH` levels less than 0.4 mIU/L.

However, in countries with iodine deficiency , especially among people over the age of 70, this condition can be as high as 15%. In Sri Lanka, this risk is low because we usually use iodized salt, but it is good to be aware.

What are the symptoms?

Most of the time, people with `Subclinical Hyperthyroidism` do not show any symptoms . That's why it's called "subclinical".

However, sometimes you may experience mild symptoms related to hyperthyroidism. At such times, you may experience things like:

• Feeling like your heart is beating fast (palpitations).
• It's like my body is shaking, just feeling nervous.
• Weight loss (despite appetite).
• Increased appetite.
• Diarrhea or frequent bowel movements.
• The skin feels thin, warm, and moist.
• Changes in women's menstrual cycle (`Menstrual changes`).

Important: Having these symptoms does not necessarily mean you have `Subclinical Hyperthyroidism`. However, if these symptoms persist, it is wise to see a doctor.

Why is this happening? What are the reasons?

Normally, our endocrine system works like a team. Think of it like a big company.

The hypothalamus, located at the base of the brain, releases a hormone called TRH (Thyroid-Releasing Hormone). This tells the pituitary gland to produce TSH.

Then `TSH` goes and tells the thyroid gland to make `T3` ​​(about 20%) and `T4` (about 80%). When these `T3` ​​and `T4` increase in the blood, it again sends a signal to the pituitary gland saying, "Okay, stop making `TSH` now, there is enough hormone." This is called the ` feedback loop` . When `T3` ​​and `T4` decrease, this cycle starts again from the beginning.

However, in `Subclinical Hyperthyroidism`, due to some problem in the thyroid gland, even though the `TSH` level is low, the production of thyroid hormones does not decrease as expected. That is why `TSH` is low, but `T3` ​​and `T4` are at normal levels.

The causes of ``Subclinical Hyperthyroidism`` are largely the same as those that cause overt hyperthyroidism. Here are some of the main causes:

• Increasing the dose of hormone therapy (levothyroxine) given for hypothyroidism (underactive thyroid). This is the most common cause.
• Multinodular toxic goiter. This is a condition in which non-cancerous lumps (nodules) develop in the thyroid gland, causing it to produce too much thyroid hormone.
• Graves' disease. This is an autoimmune condition. This means that our body's immune system attacks the thyroid gland, stimulating it to produce more hormones.
• Thyroiditis: When the thyroid gland becomes inflamed, hormone levels may temporarily increase.

How do you recognize this?

The only way to know for sure whether you have `Subclinical Hyperthyroidism` is through `thyroid function tests` . These are simple blood tests.

The normal range for TSH (also called thyrotropin) levels in a non-pregnant adult is between 0.4 and 4.5 milli-international units per liter (mIU/L).

If your blood tests show that your TSH level is low (between 0.1 and 0.4 mIU/L or less than 0.1 mIU/L), but your T4 (thyroxine) and T3 (triiodothyronine) levels are within the normal range, you have Subclinical Hyperthyroidism.

`Subclinical Hyperthyroidism` can be divided into two main categories:

• Mild: TSH levels are low, but still detectable - usually between 0.1 and 0.4 mIU/L. This level is present in 65% to 75% of people with Subclinical Hyperthyroidism.
• Severe: TSH levels are less than 0.1 mIU/L. This affects between 25% and 35% of people.

Does this need treatment?

There are actually different opinions among doctors about whether or not to treat `Subclinical Hyperthyroidism`, because there is still not enough research on the clear benefits of treatment.

Often, doctors recommend a "wait and see" approach for those with subclinical hyperthyroidism. That is, they wait for the condition to improve on its own without starting treatment.

However, treatment may be recommended for those whose TSH levels are consistently below 0.1 mIU/L, especially in the following cases:

• If you are 65 years of age or older.
• If you are under 65 years of age, have heart disease, osteoporosis, or symptoms of hyperthyroidism.
• If you are a postmenopausal woman, under the age of 65, and not taking estrogen or bisphosphonates (a type of medicine used to treat bone problems).

Subclinical hyperthyroidism during pregnancy usually does not require treatment.

If treatment is provided, what is it?

If your doctor decides that treatment is necessary, the treatment will depend on the cause of the subclinical hyperthyroidism.

• If you have a toxic multinodular goiter (a lump in the neck) or a single nodule on your thyroid, the most common treatment is radioactive iodine . This is a medicine you take by mouth. The overactive cells in your thyroid absorb the iodine. The radioactive iodine damages those cells, causing the thyroid to shrink and your hormone levels to drop over a few weeks.
• If you have Graves' disease, the most common treatments are antithyroid drugs and radioactive iodine. Antithyroid drugs such as methimazole (Tapazole) and propylthiouracil (PTU) work by blocking the thyroid gland's ability to make hormones.

Can this be prevented from happening?

In most cases, there is nothing we can do to prevent the development of `Subclinical Hyperthyroidism` or overt `Hyperthyroidism`.

However, if you don't get enough iodine in your diet (or too much) , you can develop `Subclinical` or `Overt Hyperthyroidism` due to `toxic goiter`. Although this is not common in countries like Sri Lanka because we use iodized salt, this condition can be seen in countries where iodine deficiency is common.

What can we expect with this condition? Are there any risks?

Subclinical hyperthyroidism rarely progresses to overt hyperthyroidism. However, this risk is slightly higher in people with very low TSH levels (less than 0.1 mIU/L).

Because there are many causes, everyone's `Subclinical Hyperthyroidism` is different.

Even if it does not progress to `Overt Hyperthyroidism`, `Subclinical Hyperthyroidism` can cause some complications. Some of them are:

• Atrial fibrillation ( an irregular heartbeat).
• Heart failure (risk of developing heart failure ).
• Coronary heart disease (coronary artery disease ).
• Bone loss and fractures.
• Dementia ( a condition of memory loss that can occur with age).

These risks are especially high for people over the age of 65 and those with severe subclinical hyperthyroidism.

If you are concerned about these risks, it is best to talk to your doctor about this.

When should I see a doctor?

Most of the time, if your tests show that you have ``Subclinical Hyperthyroidism,'' doctors will take the "wait and see" approach.

However, if you start to experience symptoms of hyperthyroidism (anxiety, restlessness, palpitations), be sure to see your doctor. He or she will then do another thyroid blood test to see if you have `Overt Hyperthyroidism`.

Remember, there are still many different opinions on whether or not to treat `Subclinical Hyperthyroidism`. Everyone, every situation is different. Therefore, the best thing to do is to discuss all your questions and fears with your doctor. He or she is ready and willing to help you.

Take-Home Message

Okay, so here are some things you need to remember from what we've talked about:

• ``Subclinical Hyperthyroidism`` is a condition in which the thyroid gland is only slightly overactive, but does not show major symptoms.
• This is diagnosed by a blood test that shows a low TSH level (but normal T3 and T4).
• Since there are often no symptoms, treatment may not be necessary. Your doctor may take a "wait and see" approach.
• Some people, especially older people or those with other health problems, may need treatment.
• If you experience symptoms of hyperthyroidism (such as increased heart rate, tremors, weight loss), see a doctor immediately.
• The most important thing is not to panic, talk openly about this with your doctor, and follow his advice.

I hope you find this information useful. Stay healthy!

` Subclinical Hyperthyroidism, thyroid, TSH, T3, T4, hormones, Graves' disease, goiter