An Overview Of The T3 And T4 Thyroid Hormones

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Thyroid hormones are just one of the body’s ways to keep you in top shape. Find out what they do for you.
RELATED: Frequently Asked Questions About Thyroxine And Thyroxine Test
In this article:

  1. What Are Thyroid Hormones?
  2. Where Are Thyroid Hormones Produced?
  3. How Do Thyroid Hormones Work?
  4. When Do I Know If I Have Abnormal T4 and T3 Levels?
  5. Who Are At Most Risk to Have Thyroid Hormone Problems?
  6. Why Do Thyroid Hormones Increase or Decrease?
  7. How Do I Maintain Normal T3 and T4 Levels?

Everything You Need to Know About Thyroid Hormones

What Are Thyroid Hormones?

Thyroid hormones are chemical substances produced by the thyroid gland to maintain most of the body’s processes. They are thyroxine, also called T4, and triiodothyronine, known as T3.
T3 and T4 are involved in:

  • Body development
  • Growth stimulation
  • Cellular metabolism (proteins, fats, carbohydrates, vitamins, and minerals)
  • Regulations of heart rate, body weight, cholesterol levels, and body temperature
  • Regulation neural development

The thyroid gland produces 90% more thyroxine (T4) than triiodothyronine (T3). It is around three to four times more potent than T4 in regulating the body’s metabolic processes.
T4 is usually used as a reservoir and a stepping stone in creating T3.
Most of the T3 released in the body comes from T4. T4 is converted into T3 once it reaches organs like the liver or kidneys.

Where Are Thyroid Hormones Produced?

The thyroid gland produces and secretes thyroid hormones. The production is triggered by two factors: iodine intake and the release of the thyroid-stimulating hormone (TSH).
Iodine is transformed into iodide once it gets into the bloodstream. The blood cells, then, transport the iodide into the thyroid follicles.
These thyroid follicles concentrate iodide to trigger the secretion of thyroid hormones. This also signals the pituitary gland to release TSH and regulate the T3 and T4 released by the thyroid gland.

How Do Thyroid Hormones Work?

T3 and T4 hormones are water-soluble so they can travel in the bloodstream. Carrier proteins transport them to target cells.
Once the thyroid hormones enter the cell, the inactive T4 hormones are converted into the more active T3 molecules. After the conversion, the T3 hormones will do three things:

  • Attach to cytoplasmic receptors: They act as storage in case the thyroid hormone levels within the cell drops.
  • Bind to the mitochondria: This is to increase the cell’s energy production and produce more heat and trigger faster metabolism. For example, if you are in an environment with freezing temperature, the T3 hormones stimulate the cell’s basal metabolic rate to produce higher amounts of energy which leads to body heat.
  • Binds to nuclei receptors: This, in turn, binds with the cell’s DNA. By doing so, the thyroid hormones help with cell’s growth and maturation.

RELATED: 21 Thyroid Symptoms That Tell You Something’s Not Right

When Do I Know If I Have Abnormal T4 and T3 Levels?

measuring weight | An Overview of The T3 and T4 Thyroid Hormones | t4 levels
There are a few signs and symptoms you can note to figure out if you have abnormal T4 and T3 levels.
If you are low on thyroid hormones (a case called hypothyroidism), you may experience the following:

  • Increased sensitivity to cold
  • Hoarseness
  • Weight gain
  • Fatigue
  • Constipation

On the one hand, having too much T3 and/or T4 (a case called hyperthyroidism) may lead you to experience the following:

  • Tremors
  • Anxiety
  • Rapid heart rate or palpitations
  • Abnormal weight loss
  • Excessive sweating

Thyroid hormone tests can be done to diagnose the condition:

  • Total T4 and T3 tests measure the number of thyroid hormones circulating in the body. This includes 95% of thyroid hormones (TH) that bind to plasma proteins.
  • Free T4 and T3 tests measure the 5% TH that freely circulate or are metabolically active in the body.

Plasma Proteins Definition: Bonded proteins in the blood. Major types include fibrinogen, albumin, and globulin.
Normal active TH levels vary depending on age and gender.

Who Are At Most Risk to Have Thyroid Hormone Problems?

Those with a family history of autoimmune conditions, particularly thyroid disorders, are more at risk. Hashimoto’s Disease and Graves’ Disease can be hereditary.
Women over the age of 60 are at risk to have low thyroid hormone levels. Pregnancy, on the other hand, can put females at risk of high thyroid hormone levels.
Other risk factors of thyroid hormone diseases include:

Why Do Thyroid Hormones Increase or Decrease?

High thyroid hormones in the blood may be caused by the following:

  • excessive iodine intake
  • inflammation of the thyroid gland
  • benign tumors in the thyroid and pituitary glands
  • tumors in the reproductive system
  • excessive intake of tetraiodothyronine through health supplements

Tetraiodothyronine Definition: Chemical name for iodized thyroxine (T4).
On the other hand, thyroid hormones decrease because of the following reasons:

  • a preexisting inflammatory condition of the thyroid such as thyroiditis and Hashimoto’s Disease (the prevalent cause in the US)
  • thyroid surgery
  • radiation treatment, especially on or near the neck
  • low iodine intake
  • drug side effects (e.g. lithium, interleukin-2)
  • congenital hypothyroidism

How Do I Maintain Normal T3 and T4 Levels?

Proper diet is one of the keys to maintaining your body’s health. Iodine is needed to secrete and convert T4 and T3 and so, a normal dose of it is necessary.
Below are some rich sources of iodine:

  • Seaweed
  • Iodized Salt
  • Fish (e.g. cod, tuna)
  • Seafood (e.g. shrimp, shells)
  • Dairy (e.g. Cottage cheese, yogurt)
  • Eggs
  • Prunes

For those with an already existing condition, medication is needed. Levothyroxine (Synthroid) for hypothyroidism; and methimazole (Tapazole) or propylthiouracil (PTU) for hyperthyroidism.
Learn more about the different functions of T3 and T4 hormones in this video from Blessed Health:

If you’re experiencing abnormal thyroid hormone symptoms, it’s advised that you consult your physician for diagnosis immediately. The key to managing thyroid hormone problems is early detection.
Together, you can formulate an appropriate and practical treatment and diet plan for your specific condition. You may be advised to take medications or perform specific exercises daily in order to maintain normal TH levels.
Surgery is a possibility as well depending on the severity and scope of your condition.
T3 and T4 hormones are chemical substances that affect the function of the whole body. No matter how small they are, they play a big part in keeping your body in top shape.
How do you keep your thyroid hormones in check? Let’s talk about how to take care of the thyroid gland in the comments below!
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