All about the Thyroid gland

All about the Thyroid gland

The thyroid gland is part of the endocrine system and produces thyroid hormones, which are important for metabolic health.

Where is the thyroid gland?

The thyroid is located at the front of the neck just below the Adam’s apple. It is a small, butterfly-shaped gland with two lobes located on either side of the windpipe joined by a narrow bridge called isthmus. A normal thyroid gland is not usually outwardly visible or able to be felt if finger pressure is applied to the neck.

What does the thyroid gland do?

This gland makes thyroid hormones which regulate metabolism and affect nearly every organ in the body.  Its correct functioning depends on a good supply of iodine from the diet. Iodine is the critical raw material for thyroid hormone production.  Thyroid hormones play vital roles in regulating the body’s metabolic rate, heart and digestive functions, muscle control, brain development and maintenance of bones. It is likely that all cells in the body are targets for thyroid hormones and deficiency in thyroid hormones is not compatible with normal health.

Which hormones does thyroid gland produce?

The thyroid produces are thyroxine (T4) which is relatively inactive and triiodothyronine (T3), a highly active hormone. Collectively, thyroxine and triiodothyronine are referred to as the thyroid hormones. The gland produces 80% of T4 and just 20% of T3. Once secreted by the thyroid into the bloodstream, organs such as the liver and kidneys convert T4 into the active hormone T3.

In addition, there are other hormone-producing cells within the thyroid gland called C-cells. These cells produce calcitonin. Calcitonin regulates calcium metabolism, which is important for bone health.

What is the role of iodine for thyroid health?

Iodine is a critical ‘ingredient’ for the production of thyroid hormones. Iodine is absorbed through intestine into bloodstream, then makes its way to thyroid. Thyroid uses iodine to make thyroid hormones. A daily and constant supply of this micronutrient is important to maintain a healthy thyroid.  Too much iodine at once causes thyroid to produce less hormones.

Which foods contain iodine?

Bread, eggs, dairy, iodised salt and seafood are the main dietary sources of iodine in Australia.

Who tells the thyroid to produce and release hormones? 

The thyroid is governed by a pea-sized gland located at the bottom of our brain called the pituitary gland. The pituitary gland produces and sends out a hormone called thyroid-stimulating hormone (TSH). TSH then tells the thyroid gland how much hormones to produce and secrete. TSH levels in blood rise and fall depending on the body’s needs to produce more or less thyroid hormones. 

The pituitary gland also responds to signals from the hypothalamus, which sits above the pituitary gland as part of the brain. This whole network referred to as the hypothalamic-pituitary-thyroid axis (HPT) adapts to metabolic changes and the body’s needs.

What could go wrong with the thyroid gland?

Normally the thyroid gland produces the exact number of hormones needed to keep the body’s metabolism running and in balance.  However, there are several disorders associated with the thyroid gland with most problems concerning the production of thyroid hormones. Either the thyroid gland produces too much hormone (called hyperthyroidism) or doesn’t produce enough hormone (called hypothyroidism), resulting in the body using energy faster or slower than it should.

What are typical symptoms of hyperthyroidism (overactive) and hypothyroidism (underactive)?

Typical symptoms for hyperthyroidism is weight loss, fast heart rate, irritability, nervousness, muscle weakness and tremors, infrequent menstrual periods, sleep problems, eye irritation and heat sensitivity.

Symptoms for hypothyroidism may include weight gain, slower heart rate, fatigue, more frequent and heavy menstrual periods, forgetfulness, dry skin and hair, hoarse voice and intolerance to cold. In addition, hypothyroidism is often accompanied by an enlargement of the thyroid gland known as goitre.

Who is affected by thyroid disease?

People of all ages and races can get thyroid disease. However, thyroid disorders are 5 to 8 times more likely in women than men.

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