Hypothyroidism, in other words an underactive thyroid, is the most common thyroid disfunction. Thyroid hormones influence virtually every organ system in your body. Underactive thyroid (hypothyroidism) happens when your body does not have enough thyroid hormones.

Fast reading

  1. What does the thyroid do?
  2. What is hypothyroidism?
  3. Hypothyroid (underactive thyroid) symptoms
  4. Common causes of low thyroid hormones
  5. Thyroid TEST and DON’T GUESS
  6. Thyroid self-examination
  7. Hypothyroid diagnosis – what to expect?

What does the thyroid do?

Your thyroid is a gland located in your neck. Its shape resamples a butterfly and it weights between 10-30 grams. Thyroid produces vital for us hormones. Two main thyroid hormones include T4 (thyroxine; tetra-iodothyronine) and T3 (triiodothyronine); and relatively recently discovered T2 (do-iodothyronine) and T1 (mono-iodothyronine) hormones. Thyroid makes these hormones at different quantities, for example T4 comprises approximately 87% of the entire thyroid hormone pool, T3 approximately 8%, and T2 and T1 approximately 4%. 

T4 circulates in your bloodstream and in various tissues and its job is to be available and ready for conversion to T3. Therefore, T4 is a “storage” type of thyroid hormone. On the other hand, T3 is an active thyroid hormone, meaning it powers-up your cells and facilitates energy generation, so that oxygen and glucose from foods can be converted to energy molecules (ATP) in your mitochondria.  


How much thyroid hormones you make is largely regulated by your brain, by a part called hypothalamus. Hypothalamus senses the levels of circulating T3 and T4 hormones; when their circulating levels drop, the hypothalamus “tells” the pituitary gland (also in your brain) to send thyroid-stimulating hormone (TSH) to the thyroid to promote the release of thyroid hormones. It’s called a negative feedback loop. Therefore, when T4 and T3 levels drop –TSH raises. This is what we see when someone has hypothyroidism (underactive thyroid).  

What is hypothyroidism?

Hypothyroidism, in other words an underactive thyroid, is the most common thyroid disfunction and is especially common in women 35 years old and older. Approximately 2 in 10 women 65 years of age and older have an underactive thyroid.

“Thyroid issues are more common among females than among males and the risk of thyroid problems increases with age” 

Underactive thyroid (hypothyroidism) happens when your body does not have enough thyroid hormones. It can be a result of making too little T4, and/or not converting T4 to T3 efficiently, or by dysfunctional regulation by the brain. As mentioned above, when levels of T4 and T3 drop, the levels of TSH go up to correct the hormone balance and make more thyroid hormones. In hypothyroidism however, the thyroid doesn't respond optimally to TSH (might be because of tissue destruction or lack of nutrients), as a result not enough T3 and T4 is made and distributed throughout the body, then and body functions go into the slow mode; and the pituitary keeps “shouting” by releasing more and more TSH in an effort to stimulate thyroid hormone production, unsuccessfully.  That's why TSH levels in the blood are elevated when thyroid function is low.

What is hypothyroidism?

When body cells are deprived of thyroid hormones, they will make less energy and the energy coming from foods in a form of glucose will be stored in your body as fat. Actually, every cell in your body has receptors for thyroid hormones. These hormones are responsible for the most basic aspects of our physiology, impacting all major systems of the body. Thyroid hormones directly act on the brain, the G.I. tract, the cardiovascular system, bone metabolism, red blood cell metabolism, gall bladder and liver function, steroid hormone production, glucose metabolism, lipid and cholesterol metabolism, protein metabolism and body temperature regulation. 

There are different types of hypothyroidism such as:

  • Hashimoto’s disease (most common and auto-immune),
  • goitrous hypothyroidism,
  • pituitary gland disease,
  • drug induced hypothyroidism,
  • toxin induced hypothyroidism, iodine-induced hypothyroidism.  

Hypothyroid (underactive thyroid) symptoms 

Common symptoms associated with thyroid issues are related to energy, weight, mental health, sex and fertility, hair/skin/nail health, heart health and digestive health. Symptoms can range from very mild to very severe. 

Someone suffering from hypothyroidism can struggle with:

  • weight gain,
  • tiredness/exhaustion,
  • brain fog,
  • memory problems,
  • constipation,
  • dry skin,
  • hair loss,
  • cold intolerance,
  • irregular menstruation,
  • infertility,
  • muscle stiffness and pain,
  • depression,
  • dementia,
  • hair loss,
  • brittle nails,
  • puffy skin,
  • enlarged neck,
  • infertility,
  • weak muscles. 
Hypothyroid (underactive thyroid) symptoms

If your thyroid slows down and you do not make adequate levels of thyroid hormones, your metabolism will slow down contributing to weight gain, a very common sign of an underactive thyroid.  

Depending on the cause, hypothyroidism can be a temporal situation but can also be permanent. 

If you experience 3 or more of the symptoms, it would good to asses your thyroid function by running a simple blood test. 

Common causes of low thyroid hormones

Malnutrition - lack of nutrients to allow hormone synthesis, conversion, and functioning, such as selenium, iodine, zinc, vitamin C, tyrosine, vitamin D, vitamin B12). Tip: to get adequate selenium, eat 1-3 Brazilian nuts daily.  

Suboptimal iodine levels - Lack and excess of iodine can contribute to thyroid problems. The daily recommended iodine dose ranges between 50-200 mcg (micrograms) for general population and from 200-350 mcg for pregnant and breastfeeding females. If your diet is rich in seafood, sea vegetables, seaweed, bread, dairy products, eggs, you use iodized salt and take a supplement containing iodine - you could be unconsciously getting more iodine than what your body needs. You also absorb iodine thorough skin by applying products that contain iodine, or bathing is salt solutions containing iodine.   

Impaired gut health - poor diet, impaired digestion, low stomach acid, poor bile production, intestinal dysbiosis, increased intestinal permeability

Immune dysregulation - such as an auto-immune attack against own thyroid tissue causing thyroid destruction as seen in Hashimoto’s disease

Chronic stress - suboptimal cortisol levels, too high and too low, contribute to under-conversion of free T4 to free T3 and you can end up with the symptoms of hypothyroid symptoms even though the core problem does not lie in your thyroid 

Toxins and chemicals - such as mercury, fluoride, or perchloride

Allergies and food reactions -  individuals with allergies, food intolerances or food sensitivities might be at higher risk of compromised thyroid function because of the immune triggers and a possible effect on the digestive tract.

Viral infections - respiratory infections caused by influenza virus or infections caused by mumps virus can cause subacute thyroiditis (thyroid inflammation), often associated with gradual or sudden onset of pain in the region of the thyroid gland which may persist for weeks or months. 

Radiation - treatment or exposure. Radioactive iodine is used to treat an overactive thyroid gland but it can damage the gland, causing permanent hypothyroidism. Also, radiation treatment for certain cancers (located in the head and neck) may damage the thyroid gland and/or the pituitary gland.

Medications - such as lithium (used in the management of depression or bipolar disorders), amiodarone (for management of arrythmias), interferons (in the treatment of cancer or hepatitis C). 

Inflammation - inflammation suppresses the hypothalamus-pituitary-thyroid HPT axis, decreases both the number and sensitivity of thyroid hormone receptors, decreases the conversion of T4 to T3. 

Thyroid TEST and DON’T GUESS

If you experience symptoms, I have listed above – get tested. Waiting and guessing may worsen the problem and create new problems. Untreated hypothyroidism can increase your risk for cardiovascular problems and other health issues. Keep an eye out for hypothyroidism symptoms and check your thyroid function on regular basis. 

Consider following:

  • Blood serum test for TSH, free T4, free T3, anti-TPO, anti-TG
  • Thyroid ultrasound
  • Blood serum test for vitamin D, iron, ferritin, transferrin saturation, vitamin B12, CBC with differential and a lipid panel 
Thyroid TEST

One of the biggest challenges those with subclinical hypothyroidism face is that it is often underdiagnosed. Patients have “thyroid symptoms” but they have “normal” lab results (within a normal lab range), yet not optimal if you interpret them properly.   

Typically, healthy thyroid function will be reflected by TSH levels within 0.45 and 2.5 mU/L (note that the normal lab range is slightly different 0.45 – 4.5 mU/L), the amount of available (free) T4 will be within 1.1–2.0 ng/dL, and the amount of available (free) T3 within 230-420 pg/dL. Various labs may have slightly different lab ranges. Young children and elderly typically have physiologically higher TSH levels without having any thyroid issues.  

Thyroid self-examination

If you have risk factors for thyroid diseases (such as a family history or have some symptoms), it is a good idea to feel your thyroid gland from time to time. Your thyroid gland is located in the center of your neck, below your Adams apple and above the notch of your breastbone.

Below are easy steps for examining your thyroid:

  1. Face a mirror or make a film while you are doing the examination so you can view it later.
  2. Take a sip of water (don’t swallow).
  3. Tilt your head back, while still being able to see the mirror (if you record it, you don’t have to make sure you look at the mirror or camera).
  4. When you swallow the water, look for any lumps or areas that are not the same on both sides of the thyroid.

Thyroid nodules are usually round in shape and move with the gland when you swallow. You may feel the nodule rolling underneath your fingertips or see it move when you swallow. A goiter (swelling) can be found on one side of the thyroid or on both sides.

If you find any lumps or swelling, check it with your doctor. Noteworthy, lumps or nodules on the thyroid gland do not necessarily mean that you have a thyroid disorder. Thyroid nodules are very common and often do not cause any other issues.

Hypothyroid diagnosis – what to expect?

If you were diagnosed with a hypothyroid condition, the treatment strategy may differ depending on the cause and on the severity. The symptoms may or may not be due to borderline thyroid function, and not everyone who does have subclinical disease will progress to full-fledged hypothyroidism. Sometimes, it’s essential to take thyroid hormones (forever) to compensate for their lack and sometimes lifestyle and dietary interventions together with well selected supplements might be enough to support your thyroid health, so it can bounce back and do its job well again. 

Information provided here is meant for educational purposes only, and does not constitute medical or nutritional advice or act as a substitute for seeking such advice from a qualified health professional.

Category: Diseases icon April 9 2021
Author: Dr Joanna Krzeslak-Hoogland

Being inspired by the effect of nutrition, lifestyle and mind on our health, I am dedicated to help people on their journey to wellbeing.

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