The thyroid gland makes, stores and releases hormones into the bloodstream to carry out their functions. The hypothalamus and the pituitary gland, in the brain, help control the thyroid gland.

Thyroid hormones affect almost all cell functions in the body.

Let’s talk about the function of thyroid hormones, most notably thyroxine and triiodothyronine, as well as the function of the thyroid gland.


What is the function of the thyroid gland?

The thyroid gland is responsible for producing, storing and releasing thyroid hormones that play a role in stimulating and maintaining key cell functions in the body. The thyroid hormones produced by the thyroid gland are crucial to cells are carrying out cell functions correctly.

Here is a list of thyroid gland functions:

  • Producing key thyroid hormones thyroxine and triiodothyronine, using iodine in the food you eat

  • Storing thyroid hormones thyroxine, triiodothyronine and calcitonin

  • Releasing thyroid hormones thyroxine, triiodothyronine and calcitonin

  • Communicating with the pituitary gland and hypothalamus to ensure that hormones are secreted to meet the needs of the body at any given time

The thyroid gland is responsible for maintaining homeostasis in the body. Homeostasis refers to the healthy functioning of all the body systems.

The thyroid gland ensures that if the body becomes too hot or cold, thyroid hormones are released to try and regulate the body temperature. The same can be said for when a woman is pregnant or requires more energy or is experiencing weight fluctuations.

The thyroid gland uses iodine from the foods that we eat and to produce two of the main thyroid hormones thyroxine and triiodothyronine.

The thyroid gland is closely linked to the pituitary gland and the hypothalamus, all three communicate. If thyroid hormone levels drop too low in the body, TSH (thyroid stimulating hormone) will be released from the pituitary gland. If thyroid hormone levels raise too high, TSH stops being released from the pituitary gland.

Thyroid problems can occur because of a problem in the thyroid gland itself, or a problem in communication between the pituitary gland and the thyroid or inadequate communication between the hypothalamus and the thyroid. Measuring thyroid-stimulating hormone (TSH), thyroxine (T4) and triiodothyronine (T3) circulating in the blood, helps to determine a diagnosis of hypothyroidism, hyperthyroidism or other conditions of the thyroid.

What is the function of thyroid hormones?

Thyroxine affects almost every organ in the body but there are some functions that are more notable than others.

Some of the functions of thyroxine include:

  • Regulating the metabolism
  • Stimulating digestion
  • Bone maintenance
  • Brain development
  • Cardiovascular health


Let’s explain how thyroxine carries out the above functions.

Regulating the metabolism
Thyroid hormones regulate metabolism and have been associated with weight control and obesity. Small differences in thyroid function can be associated with substantial differences in body weight. and treatment for both hypothyroidism (underactive thyroid gland) and hyperthyroidism (overactive thyroid gland) can also result in substantial weight change.

Stimulating digestion
Thyroid hormones play a role in fat metabolism, carbohydrate metabolism, protein synthesis and insulin secretion. Thyroid hormones play a role in healthy digestion. Those who are living with hypothyroidism or hyperthyroidism are prone to digestive issues.

Those who are living with hypothyroidism are more likely to suffer from constipation because of reduced gut motility. Some people living with hyperthyroidism may experience increased hunger and suffer from diarrhea, nausea and vomiting because of increased gut motility.

Bone maintenance
Thyroid hormones may affect bone calcium metabolism directly or indirectly. Thyroid hormones are required for skeletal development and hypothyroidism and thyroid issues may cause issues in bone development. Hyperthyroidism can cause an increase in risk of osteoporosis and bone fracture, even for people with subclinical disease.

Brain development
Thyroid hormones play an integral role in the development of the brain by regulating cell migration and differentiation (making sure the right type of cells develop in the right area), synaptogenesis (synapses are where two nerves meet and communicate) and myelination (myelin is the substance that covers nerve cells). Thyroid hormones also play a role in the growing embryonic brain.

Thyroid problems can cause fatigue, poor motor control, memory impairment, hyporeflexia, brain fog, depression and anxiety.

Cardiovascular health
Thyroid hormones play a role in maintaining a healthy heart rate, the elasticity of arteries, blood pressure and circulation.

Thyroid hormones influence the force and speed of the heartbeat, your blood pressure and cholesterol. If someone is experiencing hypothyroidism or an underactive thyroid, they may have a slower heart rate (bradycardia) and problems with blood pressure.If someone is experiencing hyperthyroidism or an overactive thyroid, they may have a higher heart rate (tachycardia) and higher blood pressure.

Have you ever tested your thyroid hormones? Now you can test from the comfort of home with online results and clinical support available within one week.

Written by Hannah Kingston | Medically reviewed by Gwen Murphy, PhD, MPH