Thyroid

Where Are Thyroid Hormones Produced?

The thyroid gland is an endocrine gland shaped like a butterfly, located at the front of the neck just below the Adam’s apple. It is approximately 4 cm long and 1–2 cm wide.

The thyroid gland absorbs iodine from food and combines it with the amino acid tyrosine to produce thyroid hormones:

• Triiodothyronine (T3)
• Thyroxine (T4)

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How Do Thyroid Hormones Work?

The production and release of thyroid hormones are regulated by Thyroid Stimulating Hormone (TSH), which is produced by the anterior pituitary gland.

When thyroid hormone levels in the bloodstream become too high, a negative feedback mechanism suppresses the release of TSH, causing the thyroid gland to reduce hormone production.

Conversely, when thyroid hormone levels are low, the pituitary gland releases more TSH, stimulating the thyroid gland to produce additional hormones to restore normal levels.

Thyroid hormone production is also regulated by Thyrotropin-Releasing Hormone (TRH) from the hypothalamus. TRH stimulates the release of TSH, while various other factors influence thyroid function to ensure an adequate supply of thyroid hormones for the body's needs.

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What Are the Functions of Thyroid Hormones?

Thyroid hormones play a vital role throughout the body. Nearly every organ system—including the brain, muscles, heart, and lungs—is affected by thyroid hormone activity.

These hormones are essential for:

• Cellular growth and development
• Protein and enzyme production
• Regulation of metabolism
• Maintenance of normal organ function

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Major Functions of Thyroid Hormones

1. Regulation of Growth and Tissue Development

Thyroid hormones are crucial for the growth and development of various tissues and organs, including:

• Muscles
• Skin
• Bones
• Internal organs

They also play a significant role in overall physical growth and maturation.

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2. Development of the Nervous System

Thyroid hormones are especially important for brain development during early life.

The most critical period for brain development begins around the 8th week of pregnancy and continues until approximately 3 years of age.

Insufficient iodine intake or thyroid hormone deficiency during this period may result in:

• Impaired brain development
• Permanent intellectual disabilities
• Delayed physical growth
• Developmental abnormalities

Maternal iodine deficiency, thyroid hormone deficiency, or exposure to substances that interfere with thyroid function can significantly affect a child's neurological and physical development.

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Contact Information

Kasemrad Prachachuen Hospital
950 Prachachuen Road, Wong Sawang, Bang Sue, Bangkok 10800, Thailand
Tel. +66 2 910 1600