Healthy living

The thyroid gland

What is the thyroid gland?

The thyroid gland is a key part of the human endocrine system and works together with your nervous and immune systems to regulate your body’s metabolism.

Metabolism refers to all of the processes that go on inside your body, for example, the process of turning food into energy.

The thyroid gland regulates metabolism by producing and secreting hormones into your bloodstream.

Terms explained

Autoimmune disorder – a condition where your own antibodies attack your body.

Where is the thyroid gland?

The thyroid gland is located in the lower front part of your throat, just below your Adam’s apple. It consists of 2 lobes on either side of your windpipe.

What does the thyroid gland do?

Your thyroid produces 2 important hormones:

  • Thyroxine, known as T4
  • tri-iodothyronine, known as T3.

Thyroid hormones affect your:

  • body temperature and circulation
  • appetite
  • energy levels
  • growth and bone development
  • muscle tone and suppleness
  • heart rate
  • blood sugar levels
  • central nervous system and bowel function
  • cholesterol levels
  • fat, carbohydrate and protein metabolism.

Thyroid hormones and metabolism

Your thyroid controls the chemical metabolic processes constantly taking place inside your body. This process of metabolism is how your body gets the energy it needs to survive and has a vital function.

Your body needs iodine to make thyroid hormones. Most people get suitable amounts of iodine from their diet as it is found in most food, especially seafood. Small amounts of iodine are found in vegetables grown in soils containing iodine.

If your thyroid cannot produce a sufficient amount of hormones you are vulnerable to a range of serious health conditions.

The higher the T3 and T4 iodine count that circulates in your blood the faster your metabolism is. If you have less T3 and T4, your metabolism levels drop.

If your thyroid becomes overactive (hyperthyroidism), or underactive (hypothyroidism) it is not performing normally and starts to produce abnormal chemical reactions in your body leading to:

  • disruption of your entire metabolic system
  • unusually high or low levels of hormones or enzymes
  • malfunctioning hormones or enzymes
  • a build-up of toxic substances in your body
  • diseases and serious health conditions.

Your pituitary and thyroid glands

The pituitary is an endocrine gland located at the base of your brain that controls your endocrine system, including your thyroid. The pituitary affects the thyroid by producing a hormone called thyroid stimulating hormone (TSH).

TSH causes cells within your thyroid to make more T3 and T4 hormone.

If there is too much T4 in your bloodstream your pituitary produces less TSH, which causes your thyroid activity to slow. If there is not enough T4 hormone the pituitary increases the amount of TSH to help speed up your metabolism.


A goitre is when your thyroid gland becomes significantly swollen and enlarged – this can happen if your diet is low in iodine.

If you are iodine deficient your pituitary gland may try to compensate by overstimulating your thyroid to produce more thyroid hormone. When this happens your thyroid grows larger and larger.

The presence of goitre in your neck suggests your thyroid is not functioning properly or you are iodine deficient.

Other thyroid gland disorders

Several disorders are associated with the thyroid gland:

  • Graves’ disease
  • Hashimoto’s disease
  • thyroid cancer
  • thyroid nodules
  • congenital thyroid disease
  • iodine deficiency disorder.

Hyperthyroidism – overactive thyroid

Hyperthyroidism is a condition where your thyroid is overactive and releases too many T4 and T3 hormones into your bloodstream, creating a hormonal imbalance and causing your metabolism to speed up.

The most common cause of hyperthyroidism is an autoimmune condition called Graves’ disease.

Learn more about hyperthyroidism, including Graves’ disease and the symptoms and treatment of an overactive thyroid.

Hypothyroidism – underactive thyroid

Hypothyroidism is a condition where your thyroid is underactive and releases too little T4 and T3 hormones into your bloodstream.

This causes your metabolism to slow down too much and reduces the thyroid’s ability to make hormones.

The most common cause of hypothyroidism is an autoimmune condition called Hashimoto’s disease.

Learn more about hypothyroidism, including Hashimoto’s disease and the symptoms and treatment of an underactive thyroid.

Where to get help

  • See your doctor
  • See your endocrinologist
  • Visit a GP after hours
  • Ring healthdirect Australia on 1800 022 222.


  • People with a family history of thyroid conditions have a higher risk of also getting thyroid and other autoimmune conditions.
  • An overactive thyroid (hyperthyroidism) releases too much T4 and T3 into your blood stream and causes your metabolism to speed up.
  • An underactive thyroid (hypothyroidism) does not release enough T4 and T3 into your blood stream and causes your metabolism to slow down too much.
  • Thyroid conditions can be treated and have a good prognosis.
  • Thyroid conditions affect more women than men.


Diabetes and Endocrine Health Network

This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.

Link to HealthyWA Facebook page