the thyroid

Understanding the Thyroid: Function, Hormones, and Common Conditions

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Updated on March 17, 2024

Deep within your throat lies a small, butterfly-shaped something called the thyroid. Despite its unassuming size, the thyroid plays a critical role in orchestrating your body’s well-being. Think of it as a silent conductor, regulating essential functions through the production of powerful hormones. These hormones influence a wide range of processes, from governing your metabolism and energy levels to impacting your mood, heart rate, and even brain function.

This article delves into the fascinating world of the thyroid, exploring its function, the hormones it produces, and how it impacts your overall health. We will also discuss common thyroid conditions and the importance of maintaining optimal thyroid function for a vibrant and healthy life.

Anatomy of the Thyroid

the thyroid

So, first things first, what kind of organ is this thyroid?

The thyroid is an endocrine gland located in the lower front part of the neck, just above the collarbone. More specifically, it lies in close proximity to the trachea, and its position can be palpated just below the prominence of the Adam’s apple in males (known as the laryngeal prominence).

Often referred to as the body’s metabolic control centre, the thyroid is a pretty critical component of the endocrine system. It is characterised by a distinctive butterfly or bowtie shape with a spongy and pliable texture, and it is composed of numerous follicles. These are tiny sacs that contain a gel-like substance known as colloid.

The thyroid has two lobes on either side of the trachea (windpipe) connected by a narrow band of tissue called the isthmus, forming the complete structure. Although relatively small, the thyroid’s size can vary among individuals. On average, each lobe of the thyroid is about 4-6 centimetres long, and the isthmus adds to its overall dimensions.

Richly vascularised, the thyroid gland receives a significant blood supply to facilitate the transport of hormones and nutrients. As we will see in a bit, the thyroid gland is primarily responsible for synthesising and secreting two key hormones: thyroxine (T4) and triiodothyronine (T3), both of which contribute to regulating various physiological functions throughout the body.

Thyroid Hormones

The thyroid gland is a powerhouse of hormone production, releasing those two primary hormones we mentioned three lines ago: thyroxine (T4) and triiodothyronine (T3) and to understand T4, we must first talk about T3.

The triiodothyronine hormone of T3 is named for its three iodine atoms, making it the more biologically active form of thyroid hormone. It is formed by the removal of one iodine atom from T4, which has four iodine atoms. Such a process occurs mainly in peripheral tissues. Some T3 is also directly secreted by the thyroid gland.

T3 is the hormone that exerts the majority of the thyroid’s physiological effects. It influences the body’s metabolism, energy production, and overall growth and development. Its levels are tightly regulated by the hypothalamus and pituitary gland through a feedback loop. When they are low, the pituitary releases the thyroid-stimulating hormone (TSH), which prompts the thyroid gland to generate more T4 and, subsequently, T3.

On the other hand, T4 is practically the most abundant thyroid hormone created by the thyroid gland, and it is so named because it contains four iodine atoms. It is synthesised within the follicular cells of the thyroid gland and is stored in small sacs called follicles.

While T4 is the predominant hormone secreted by the thyroid, it is relatively inactive compared to T3. As we mentioned earlier, peripheral tissues, particularly the liver and kidneys, convert T4 into the more active T3 through the removal of one iodine atom.

In other words, T4 serves as a precursor to T3 and acts as a reservoir for the active thyroid hormone. It circulates in the bloodstream, awaiting conversion into T3 when the body requires an increased metabolic rate.

Thyroid Function

the thyroid

Together, T4 and T3 orchestrate the thyroid’s influence on metabolism, energy balance, and the overall functioning of organs and tissues. The delicate balance between these hormones is crucial for maintaining homeostasis and ensuring the body’s optimal performance. Imbalances in T4 and T3 levels can lead to thyroid disorders.

Let’s explore in a little more detail how those two hormones help maintain health and well-being.

Metabolism Regulation

The thyroid hormones, thyroxine (T4) and triiodothyronine (T3), exert a profound influence on the body’s metabolic rate, playing a central role in regulating energy production and calorie consumption.

Basal Metabolic Rate, or BMR, refers to the minimum amount of energy the body needs to maintain basic physiological functions while at rest. Thyroid hormones directly influence BMR by increasing the rate at which cells use oxygen and produce energy. Elevated levels of T4 and T3 stimulate cellular metabolism, leading to increased energy expenditure even when the body is at rest.

Secondly, thyroid hormones enhance the breakdown of nutrients, particularly carbohydrates and fats, to generate energy. Such an increased metabolic activity promotes the efficient utilisation of glucose for energy production. This process is pivotal for providing energy to cells, tissues, and organs throughout the body, supporting various physiological functions.

Speaking of other macronutrients, T4 and T3 influence the metabolism of proteins and fats. While breaking down protein impacts muscle development, repair, and overall protein turnover, lipid metabolism is also affected by the breakdown of fats for energy production.

On a broader scale, thyroid hormones play a critical role in determining how efficiently the body utilises calories from the food we consume. When there is a balance between the levels of T4 and T3, calories are effectively converted into usable energy, preventing the accumulation of excess calories as fat.

The opposite is also true. In conditions where thyroid function is impaired, calorie consumption is reduced, creating a potential predisposition to weight gain.

Body Temperature Control

Another interesting point about the thyroid function is that it contributes to the body’s ability to generate heat. As the metabolic activity increases thanks to T4 and T3 doing their job properly, heat is produced as a byproduct, which helps maintain a stable internal body temperature.

This thermogenic effect is vital for preventing hypothermia—this is a medical condition in which the body loses heat way faster than it can compensate for and practically gets itself in big, unpleasant trouble. By modulating metabolic activity, the thyroid helps regulate heat production and distribution, contributing to the maintenance of a stable internal body temperature.

In addition to promoting heat production, the thyroid also influences mechanisms that aid in heat dissipation. Proper thyroid function ensures efficient blood circulation, enabling the transport of heat throughout the body. This helps dissipate excess heat through the skin, regulating body temperature within a narrow range.

A well-functioning thyroid is also crucial for adapting to cold environments. Both T4 and T3 influence the body’s response to cold stress by promoting shivering, a mechanism that generates heat to maintain optimal body temperature. Additionally, the thyroid helps regulate the constriction and dilation of blood vessels in response to temperature changes, optimising blood flow to conserve or release heat as needed.

Hypothyroidism and Hyperthyroidism


Everything we mentioned in the previous section happens spontaneously as long as the thyroid is functioning well. Once something goes wrong, the entire body function is affected, and this can be pretty clear when the gland is either overdoing or underdoing its job. So, let’s explore those two conditions.


An underactive thyroid, clinically known as hypothyroidism, happens when the gland fails to produce sufficient T4 and T3. This deficiency can have widespread effects on the body, impacting energy levels, metabolism, weight, and mental well-being.

Let’s explore the causes, symptoms, and potential consequences of hypothyroidism.


The most common cause of hypothyroidism is an autoimmune condition called Hashimoto’s Disease, where the body’s immune system mistakenly, and stupidly, attacks the thyroid gland, leading to inflammation and reduced hormone production. Another cause is related to iodine deficiency, which happens when the body does not get enough iodine from food, causing the thyroid to produce less hormones than needed to maintain a proper body function.

Surgical removal of the thyroid or exposure to radiation therapy in the neck area can also impair thyroid function. While certain medications, such as lithium and amiodarone, can interfere with thyroid hormone production, some individuals are actually born with an underactive thyroid.


One of the hallmark symptoms of hypothyroidism is persistent fatigue, often described as feeling tired despite adequate rest, with muscle weakness and joint pain. As reduced amounts of T4 and T3 lead to a slower metabolism, there is a chance of weight gain even with a consistent diet. Slowed digestion is also a common symptom and is often accompanied by constipation.

Remember that thing about heat production? A consequence of hypothyroidism is feeling unusually cold. Skin can also become coarse and dry, and hair can become brittle. Women with hypothyroidism can experience disrupted menstrual cycles in terms of irregularities or changes in flow.

It does not stop here, which can clearly show how pivotal this small gland is. An underactive thyroid can potentially impact mental well-being, with symptoms ranging from mild depression to cognitive difficulties and memory issues.


Untreated hypothyroidism can lead to serious consequences. For example, it contributes to elevated cholesterol levels and increases the risk of heart disease. In severe cases, prolonged untreated hypothyroidism can lead to myxedema, a rare but life-threatening condition characterised by extreme fatigue, lethargy, and unconsciousness.

Hypothyroidism can also affect reproductive health, leading to fertility issues and menstrual irregularities. 


An overactive thyroid, known as hyperthyroidism, occurs when the thyroid gland produces an excess of its two dear crucial hormones. Like with the previous condition, let’s explore the causes, symptoms, and consequences of this heightened hormonal activity.


Graves’ Disease is an autoimmune disorder and is by far the most common cause of hyperthyroidism. It causes the immune system to produce antibodies that stimulate the thyroid to overproduce hormones. The presence of multiple nodules (lumps) on the thyroid can lead to the excessive production of hormones as well.

Another cause of hyperthyroidism is any inflammation of the thyroid caused by a viral infection. This can cause a temporary increase in hormone levels. Since the lack of iodine causes hypothyroidism, it makes sense that consuming too much iodine, either through diet or medications, can trigger hyperthyroidism.


An overactive thyroid leads to increased metabolic activity, which increases appetite. Paradoxically, some individuals may experience fatigue or weakness and unexplained weight loss. They may also feel rapid or irregular heartbeat and heightened anxiety, irritability, and nervousness.

As expected, individuals with hyperthyroidism may feel excessively warm and intolerant to heat with fine tremors, especially in the hands. Women may experience changes in menstrual patterns, including lighter or less frequent periods.


Persistent high levels of thyroid hormones can strain the cardiovascular system, leading to conditions such as hypertension, palpitations, heart failure, and an increased risk of stroke. Hyperthyroidism can accelerate bone turnover, increasing the risk of osteoporosis and fractures.

In severe cases, untreated hyperthyroidism can lead to a life-threatening condition called thyroid storm, characterised by extreme hyperactivity, fever, and cardiovascular collapse.

Additionally, hyperthyroidism can contribute to psychological symptoms, including anxiety disorders and, in severe cases, psychosis.

Thyroid Health and Lifestyle

the thyroid

Maintaining thyroid health involves a combination of lifestyle habits, dietary choices, and medical management. Here are some tips to help keep your thyroid healthy:

  1. Balanced Diet: Make sure your diet is abundant with nutrients essential for thyroid function, including iodine, selenium, zinc, and vitamins A, D, and E. Foods like seaweed, seafood, Brazil nuts, dairy products, eggs, and lean meats can help support thyroid health.
  1. Limit Processed Foods: Minimise consumption of processed and junk foods, refined sugars, and unhealthy fats, as they can negatively impact thyroid function and overall health.
  1. Manage Stress: Chronic stress can affect thyroid function. Practise stress-reducing techniques such as meditation, yoga, deep breathing exercises, or hobbies you enjoy to promote relaxation.
  1. Adequate Sleep: Aim for seven or eight hours of good sleep each night to support overall health, including thyroid function. Establish your bedtime routine and create a sleep-friendly environment to improve sleep quality.
  1. Regular Exercise: Do regular physical activity to support metabolism and overall well-being. Choose activities you enjoy, like walking, jogging, swimming, or yoga, and aim for at least 30 minutes of moderate exercise most days of the week.
  1. Thyroid Medication Adherence: If you have a thyroid condition requiring medication, take it as prescribed by your healthcare provider. Regularly monitor your thyroid hormone levels and discuss any changes or concerns with your doctor.
  1. Limit Environmental Toxins: Reduce exposure to environmental toxins such as pollutants, heavy metals, and endocrine-disrupting chemicals found in plastics and certain household products.
  1. Regular Check-ups: Schedule regular check-ups with your healthcare provider to track thyroid health and address any concerns or symptoms promptly.
  2. Avoid Smoking: If you smoke, consider quitting. Smoking has been linked to thyroid dysfunction and can interfere with thyroid medication effectiveness.


The thyroid gland, though small, exerts a mighty influence on our entire body. Understanding its function and the impact of its hormones empowers us to prioritise our well-being. Maintaining a healthy lifestyle by eating balanced diet, regular exercise, and managing stress can contribute positively to thyroid health.

However, for individuals experiencing symptoms suggestive of thyroid dysfunction, consulting a healthcare professional is crucial for diagnosis and appropriate treatment. Early detection and suitable management of thyroid conditions can ensure optimal function and a life filled with vitality.

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