In this video, I will give a simplified explanation of how the thyroid works and how the other organs in the brain help it work. This knowledge will support you in understanding how your thyroid knows the right amount of hormone to produce in a healthy body.

You won’t be a thyroid expert at the end of this series, but you will definitely be able to look at your thyroid bloodwork and understand a lot about your thyroid function as well as some other body functions.

The body relies on three structures in the hypothalamus-pituitary-thyroid axis to produce thyroid hormones and to know how much hormone to send into the body:

• The hypothalamus - found in the brain
• The anterior pituitary gland - found in the brain
• The thyroid gland - a butterfly-shaped gland located in the front of the neck.

We will start with learning what the normal process looks like before we dive into learning about abnormal findings.

In a nutshell

Hypothalamus & Pituitary

The hypothalamus produces a hormone called thyrotropin-releasing hormone, aka, thyroid releasing hormone, or TRH.

TRH communicates with the anterior pituitary gland (just below the hypothalamus). TRH tells the anterior pituitary gland to release the thyroid-stimulating hormone (TSH). The amount of TSH released depends on the circulating levels of thyroid hormones detected in the blood.

Thyroid

Inside the thyroid, the following are stored:

• Thyroglobulin (TG)
  • A precursor protein that stores iodine needed to make thyroid hormone.
  • Stores and releases thyroid hormones into the bloodstream.
• Thyroid peroxidase (TPO) - A thyroid enzyme that accelerates the oxidation of iodide to form iodine atoms that are needed to create the thyroid hormones your body uses.
• Thyroxine (aka tetraiodothyronine or T4). This is the primary thyroid hormone. Think of it as stored thyroid hormone.
• Triiodothyronine (aka T3) - This is the thyroid hormone that is usable by the body. This is made from T4. Once made, it is only usable by the cells for a few hours, so the body is constantly making more of it from the hormone T4 by breaking off an iodine molecule.

I want to break down the words tetraiodothyronine and triiodothyronine because that can be useful in making sense of the process:

• Tetra = 4 - referring to # of iodine molecules
• Tri = 3 - referring to # of iodine molecules
• Iodo = iodine molecules
• Thyronine = name for thyroid hormone.

Tetraiodothyronine (T4) = thyroid hormone with 4 iodine molecules - stored thyroid hormone.

Triiodothyronine (T3) = thyroid hormone with 3 iodine molecules - usable thyroid hormone made from T4 by removing one iodine molecule.

Why does this all matter? Thyroid hormones are critical to many body processes. Every cell in the body needs thyroid hormone in order to work properly. Thyroid hormone is involved with:

• Regulating weight and various metabolism functions
• Energy levels
• Body temperature
• Brain function
• Skin/hair/nail health
• Growth in children
• Heart function
• Skeletal and muscle function
• Digestive health
• Bone maintenance
• Thyroid hormones affect the balance of other hormones like testosterone, estrogen, and progesterone
• More

How well the thyroid is working influences how well all your cells in your body are working and your overall health.

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