Thyroid Hormones. What are T3, T4, and TSH?

Thyroid hormones
What are T3, T4, and TSH?

Thyroid diseases are complex, variable, and highly individual, meaning thyroid problems will look very different for each person. In any case, it is important to have a general understanding of how the thyroid works and what hormones it produces.

This understanding can help you advocate for your interests and ask the right questions when visiting a doctor. It can also give you insight into some of those mysterious symptoms you may be experiencing.

First of all: the thyroid gland is an integral part of the endocrine system, which is a collection of glands that produce all the important hormones responsible for metabolism, growth, sexual function, sleep, and your mood.

The gland, tiny and butterfly-shaped, is located in the lower front part of the neck. It produces two main thyroid hormones, triiodothyronine (T3) and thyroxine (T4), both of which play an important role in your energy levels, internal temperature, hair, skin, weight, and much more.  

When the level of thyroid hormones decreases, several problems may arise.  

You may have an overactive thyroid gland, which produces too much thyroid hormone (hyperthyroidism). An example of this is Graves’ disease.  
You may also have reduced thyroid activity, where too few thyroid hormones are produced (hypothyroidism). An example of this is Hashimoto’s thyroiditis.

Understanding the Two Main Thyroid Hormones: T3 и T4

The thyroid gland is regulated by both the hypothalamus (located in your brain) and the pituitary gland, a pea-sized gland at the base of your skull.  

The hypothalamus releases thyrotropin-releasing hormone, which then causes the pituitary gland to produce thyroid-stimulating hormone (TSH). It is TSH that helps the thyroid gland release T4 and T3. Without TSH, the system would fail.

Thyroxine (T4) is responsible, among other things, for your metabolism, mood, and body temperature. T3 is also produced in the thyroid gland and can also be produced in other tissues of the body by converting T4 (in a process called deiodination) into T3. This hormone is central to your digestive and metabolic function and also monitors bone health.

So, if your T3 and T4 levels are too low, the pituitary gland will secrete more TSH. If they are too high, the gland will secrete less TSH, but this feedback system only works if everything is functioning properly.

When you have too much T3 or T4, you may experience:

• Anxiety
• Feeling of irritation
• Hyperactivity
• Hair loss
• Irregular menstruation
• Tremor and Shaking
• Excessive sweating

When you have too much T3, you may experience thyrotoxicosis, a condition that arises from an overactive thyroid gland or hyperthyroidism.

It is also important to note that hormone levels are very complex. For example, an elevated level of free T4 along with a low level of TSH may indicate hyperthyroidism.

When you have too little T3 or T4, you may experience:

Weight gain
Memory issues
Fatigue
Constipation
Different Degrees of Consciousness Impairment
Dry skin

Understanding Thyroid-Stimulating Hormone (TSH)

As mentioned above, thyroid-stimulating hormone (also known as thyrotropin or thyrotropin) is produced by the pituitary gland. It acts as the “master of hormones” and controls the production of T3 and T4 from its control center.

If you have too much TSH, it may mean that your thyroid gland is not producing enough T3 or T4. Remember, TSH should stimulate the thyroid gland, but if the gland does not respond, it means there is too much TSH in your body.

If your TSH level is too low, it may mean that your thyroid gland is producing too much thyroid hormone. This excessive thyroid production can actually suppress TSH.

Attention to pregnant women: It is incredibly important for your hormones to be balanced during pregnancy, as the thyroid-stimulating hormone plays a significant role in the development of a healthy fetus

Diagnosis of Thyroid Condition

There is no single test for every situation; there are several types of thyroid examinations. If you are concerned about thyroid issues or if your hormones are unbalanced, your doctor may order an initial blood test for TSH levels. This is because TSH levels can signal other, more specific problems.

What is the normal TSH level?  

If your results are somewhere between 0.4-4.0 mIU/L, you are in the “normal” range. However, there are studies suggesting that the reference range for TSH should be narrowed to 0.4–2.5 during pregnancy.

As a rule, a healthy TSH level indicates that the entire system is functioning well, but this is at best a simplification. A normal T3 level can range from 100 to 200 nanograms per deciliter (ng/dL), while a normal T4 level ranges from 5.0 to 12.0 micrograms per deciliter (µg/dL)  

Free T4, which determines the amount of T4 available in the body, should be in the range of 0.8 to 1.8 nanograms per deciliter (ng/dL)

However, it is important to note that different laboratories and doctors may have different “normal ranges.” There is also no single laboratory test that can accurately tell you what might go wrong or be absolutely precise in diagnosis, so you may need several different tests. Additionally, you may need a thyroid ultrasound or biopsy to determine the exact cause of your symptoms or hormone level imbalance. There are several different thyroid diseases, each with its own root causes. Your endocrinologist or thyroid specialist will know what to check for, as there are many different tests depending on your specific condition and level.

Questions to Ask an Endocrinologist

What tests do I need to check my thyroid levels?
What are the normal ranges for each hormone?
Are my T3, T4, and TSH levels normal?
Do my symptoms indicate a thyroid disease?
How can we fix any issues with levels using medication or lifestyle changes?
Are there any side effects of the medications?
How long should it take before the medication starts to work?

Support for a Healthy Thyroid

Now that you have a general understanding of thyroid function, you might be wondering if there are ways to support thyroid health beyond medication. This is important because sometimes it may take a while for medications to correct hormonal imbalances. In this case, the best thing you can do is change your lifestyle.

Eat well

There are no diets or protocols for the thyroid gland.

But it is important to eat properly and in a balanced way.

Avoid non-nutritious foods or products full of empty calories; this will only worsen any feelings of fatigue or sluggishness caused by thyroid issues. Give up processed foods (anything in bags or boxes), candies, sodas, and junk food, and reduce their consumption.  

Movements

Exercise is crucial, but it’s important to coordinate any exercise with a doctor. This is because patients with hyperthyroidism (who already have an increased metabolism) may experience heart problems if they overtrain.  

Lilia Albertovna Barsukova (Kuzina)
Endocrinologist-Dietitian