How to improve an underactive thyroid
ThyroidWomen's Health

How to improve an underactive thyroid

Written by

Lauren Dobischok
9 May, 2023

Medically checked article All HOMED-IQ content is reviewed by medical specialists

The thyroid gland is considered underactive when it does not produce enough thyroid hormones to meet your body’s needs. This is also called hypothyroidism. The thyroid plays a central role in many processes in the body, and both an underactive and overactive thyroid can cause serious health problems. Hypothyroidism may cause little to no symptoms in the beginning, but long-term untreated hypothyroidism can cause unpleasant physical symptoms and increase the risk of chronic diseases, such as nerve damage and heart problems (Mayo Clinic, 2022). In this blog, we’ll cover the symptoms and causes of hypothyroidism, as well as ways you can improve the function of an underactive thyroid.

What does the thyroid gland do?

The thyroid gland is a small gland located in the front part of the neck. It is part of the endocrine system- a network of organs that controls many important functions in the human body through the production and release of certain hormones. The most important function of the thyroid gland is to control metabolism and therefore energy production and release in the body. All the cells in your body need energy to function. If your thyroid gland is not functioning properly, it can have a negative impact on your entire body (Cleveland Clinic, 2022). 

The importance of thyroid hormones 

To understand how hypothyroidism occurs, it is important to know the basics about the different thyroid hormones. The production and secretion of thyroid hormones are regulated by the hypothalamus, located in the brain. The hypothalamus first releases thyroid-releasing hormone (TRH), which stimulates part of the pituitary gland in the brain to release thyroid-stimulating hormone (TSH). TSH then stimulates the thyroid gland to release thyroxine (T4) and triiodothyronine (T3) (Cleveland Clinic, 2022). The amount of TSH in the blood fluctuates depending on how much T3/T4 are present. If the thyroid is underactive, T3 and T4 levels are low and the level of TSH is high.The thyroid gland requires iodine to create thyroid hormones. Since our bodies cannot produce iodine on their own, it must be obtained through food (especially iodised table salt) and water. Both too much or too little iodine in your body can impact the production and release of thyroid hormones (IQWiG, 2010).  The two main thyroid hormones are:

  • Tetraiodothyronine (thyroxine/T4): A distinction is made between bound T4, which is bound to proteins in the blood, and free T4 (FT4), which can be converted by the body into the active hormone T3. This is also called deiodination.
  • Triiodothyronine (T3): T3 is also present in the body in bound and free forms (FT3). 

Together, T4 and T3 control your body’s energy consumption and thus affect almost all of your body’s organs. They affect metabolism, respiration, digestion, body temperature, fertility, and brain development (Cleveland Clinic, 2022). Furthermore, the thyroid gland produces the hormone calcitonin, which is involved in calcium and bone metabolism (IQWiG, 2010).  

What is the difference between hypothyroidism and hyperthyroidism?

While hypothyroidism refers to an underactive thyroid that does not produce enough thyroid hormones, hyperthyroidism is the opposite. During hyperthyroidism, the thyroid is overactive and produces too many thyroid hormones. Hyperthyroidism increases the body’s metabolism and can lead to symptoms, such as weight loss, trembling of the hands, and a fast or irregular heartbeat (Mayo Clinic, 2022). If the thyroid is overactive, generally the amount of T3/T4 in the blood is high and the level of TSH is low. 

What are the symptoms of hypothyroidism?

The symptoms of hypothyroidism depend on the severity of the disease. Most symptoms develop gradually, often over several years.

  • Fatigue and weakness
  • Sensitivity to cold
  • Dry skin and thinning hair
  • Unwanted weight gain
  • Muscle weakness, muscle pain and stiffness
  • Irregular or heavy menstrual cycles
  • Slowed heart rate (bradycardia)
  • Depression

Source: Mayo Clinic, 2022

Causes of hypothyroidism

Hypothyroidism occurs when the thyroid does not produce enough thyroid hormones and can have primary or secondary causes. Primary hypothyroidism is caused by a condition that directly impacts the thyroid, making it unable to produce adequate thyroid hormones. Secondary cause hypothyroidism occurs when something impacts the pituitary gland’s ability to produce TSH, which directs the thyroid to produce thyroid hormones (Cleveland Clinic, 2020). Causes of primary hypothyroidism include: 

  • Autoimmune conditions: the most common cause of hypothyroidism is Hashimoto’s disease. This is an autoimmune disease in which the body’s immune system attacks and damages the thyroid gland (NIDDK, 2021). The causes of Hashimoto’s disease are unclear, but genetics appear to play a role. 
  • Inflammation of the thyroid gland (thyroiditis): When the thyroid gland becomes inflamed, the level of thyroid hormones may initially increase in the blood as stored hormones are released. This is also known as thyrotoxicosis.  If the inflammation remains untreated, hypothyroidism results.
  • Congenital hypothyroidism: This is an underactive thyroid gland that is detected at birth.  
  • Medical and surgical interventions: As part of treatment of other thyroid diseases such as thyroid nodules (benign thyroid tumours), part or all of the thyroid gland may be removed.
  • Radiation treatment of the thyroid gland: Treatment with radioactive iodine, for example, for hyperthyroidism or tumors in the head and neck, can damage thyroid tissue and cause hypothyroidism. 
  • Certain medications: Some medications can interfere with the production of thyroid hormones and lead to hypothyroidism. These include certain heart medications and certain cancer medications.
  • Iodine deficiency: In rare cases, iodine deficiency can also cause hypothyroidism. 

Source: NIDDK,2021

The most common secondary causes of hypothyroidism are tumors of the pituitary gland (Mayo Clinic, 2022).

Diagnosing hypothyroidism

Because thyroid hormones perform several important functions in our bodies, it is important to maintain levels that are neither too high nor too low. Thyroid problems are diagnosed by checking the level of thyroid hormones in the blood (NHS, 2021). If you have symptoms you suspect could be due to a thyroid problem, it is important to get tested so treatment can begin as soon as possible. You can either arrange this with your GP or do it from home, including using a home test from Homed-IQ. Homed-IQ’s Thyroid Blood Test measures the level of free T3, T4 and TSH in your blood. After collecting the finger prick blood sample and mailing it to our certified partner laboratory, the sample is analysed and the results are sent to your online account. The test laboratory report can be printed and shared with your doctor if follow-up care is needed.

Treatment of hypothyroidism

Hypothyroidism is very treatable with correct medication, and people with hypothyroidism can live normal and healthy lives with correct medical care. Treatment for hypothyroidism usually involves taking the hormone replacement medication levothyroxine daily. This medication is taken orally and increases the amount of thyroid hormones in the body. Depending on the cause and severity of hypothyroidism, people with an underactive thyroid may need to take medication throughout their lives to maintain normal thyroid hormone levels. In very mild forms, hypothyroidism may also improve on its own (Cleveland Clinic, 2020). However, all hypothyroidism should be monitored by a doctor.

Complications of untreated hypothyroidism

As thyroid hormones are essential for metabolism, untreated hypothyroidism can lead to elevated low-density-lipoprotein cholesterol (LDL) and serious heart problems such as heart failure and heart disease. A goiter (enlargement of the thyroid) can also develop, which can cause difficulty swallowing and breathing (Mayo Clinic, 2022). Long-term hypothyroidism can also impact fertility and cause nerve damage (neuropathy) over time. Prompt diagnosis of hypothyroidism is especially important in pregnant women. Untreated hypothyroidism during pregnancy can increase the risk of birth defects, and sufficient thyroid hormones are important for normal brain development and fetal growth (Johns Hopkins, 2023). 

How can I improve my thyroid function?

  • Know your risk: To ensure that hypothyroidism is detected early, it is important that you pay attention to possible symptoms and get tested if needed.  Women are especially more likely to be affected by hypothyroidism than men, as well as people over the age of 60 (NIDDK, 2021).
  • Support your energy levels: Many people with hypothyroidism experience fatigue and weakness. For this reason, it is important to support the body with healthy lifestyle habits. These include drinking enough water, practising regular moderate exercise, getting a good night’s sleep, and managing stress (NHS, 2021).
  • Eat foods that support good thyroid function:
    • Iodine: As iodine is required for our bodies to make thyroid hormone, sufficient iodine is necessary for optimal thyroid function. Most people consume sufficient iodine through iodised table salt or other foods fortified with iodine. Other foods that contain iodine include cheese, cow’s milk, eggs, saltwater fish, and soy sauce (Cleveland Clinic, 2022).
    • Vitamin B: Vitamin B12 deficiency is common in hypothyroidism, with one study finding approximately 40% of hypothyroid patients had low vitamin B12 (Jabbar et al., 2008). Vitamin B12 is primarily found in foods of animal origin, including fish, poultry, eggs, and dairy products (NIH, 2022).
    • Selenium: This nutrient has important functions in the formation and metabolism of thyroid hormones. Pork, beef, turkey, fish, shellfish, and eggs contain large amounts of selenium. Some beans and nuts, such as Brazil nuts, are also rich in selenium (NIH, 2021). Adequate levels of selenium are essential for preventing thyroid diseases such as hypothyroidism (Ventura et al., 2017).
    • Vitamin D: Low levels of vitamin D are associated with autoimmune-related hypothyroidism. People with Hashimoto’s thyroiditis, an autoimmune thyroid disease, have lower levels of vitamin D than the general population (Mackawy, 2013). In addition to spending time in the sun, vitamin D levels can also be obtained from foods such as oily fish (salmon, tuna, mackerel, and sardines), beef liver, mushrooms, or egg yolks (Cleveland Clinic, 2022).
    • Avoid foods that interact with thyroid medication: If you have already been diagnosed with hypothyroidism and are taking medication, some foods may alter the effects of the medication. Avoid taking your thyroid hormones at the same time as walnuts, soy flour, calcium supplements, and iron supplements or iron-containing multivitamins. (Mayo Clinic, 2021).


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About the author

Lauren Dobischok

Lauren is a health scientist and science communicator currently living in the Netherlands. Originally from Canada, she completed a Research Master’s in Health Sciences at the Netherlands Institute of Health Sciences at Erasmus University Rotterdam (NIHES) with a specialisation in epidemiology. Prior to her master’s degree, she completed a Bachelor’s degree in Health Sciences at Simon Fraser University. With a background in public health, her goal is to create accurate scientific content that is easy to understand and empowers people to make informed decisions. Within Homed-IQ, Lauren works as a Product Developer and Content Lead, working closely with physicians and scientists on medical devices for Homed-IQ’s new products and written communications.