Thyroid Hormones and the Thyroid Gland

• The thyroid gland, a butterfly-shaped organ located in the front of the neck, plays a crucial role in the body's endocrine system.

• It produces thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), which are essential in regulating the body's metabolism, growth, and function.

Synthesis of Thyroid Hormones: 

The synthesis of thyroid hormones involves several steps:

1. Iodide Trapping: Thyroid follicular cells absorb iodide from the bloodstream.

2. Transport to the Colloid: Iodide is transported to the lumen (colloid) of the thyroid follicle.

3. Oxidation and Iodination: The iodide is oxidized to iodine, which then attaches to tyrosine residues in the protein thyroglobulin, forming monoiodotyrosine (MIT) and diiodotyrosine (DIT).

4. Hormone Formation: Coupling of these iodinated tyrosines leads to the formation of T3 (one MIT plus one DIT) and T4 (two DIT molecules).

5. Release into Bloodstream: Thyroglobulin is taken back into the follicular cell, where T3 and T4 are released from the protein and then secreted into the bloodstream.

6. Conversion of T4 to T3: In peripheral tissues, T4 is often converted to the more active T3 through deiodination.

Here is a flowchart diagram illustrating the Synthesis of Thyroid Hormones:

Flowchart of synthesis of thyroid hormones

Functions of Thyroid Hormones

• Regulate metabolism and energy.

• Support brain development, protein synthesis, and cell growth.

• Influence fat, protein, and carbohydrate metabolism.

• Essential for bone health and muscle control.

Thyroid Disorders

1. Hypothyroidism: Low thyroid hormone production, causing fatigue, weight gain, and depression.

2. Hyperthyroidism: Excess hormone production, leading to weight loss, anxiety, and rapid heartbeat.

Proper thyroid function is crucial for overall health, and disorders require accurate diagnosis and management.