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Hypothyroidism: Symptoms, Causes & Treatment

What is Thyroid Gland?

The thyroid gland is one of the primary endocrine located in the neck of a person. The main function of the thyroid gland is to regulate and maintain the functioning of all organs of a body by controlling the metabolic rate. This includes the heart rate, blood pressure, cell production, brain development, and bone maintenance. Another function of the thyroid gland is to convert consumed food into energy without converting it into complete wastage because the thyroid gland is responsible for protein synthesis and metabolism of the fats and carbohydrates present in the food. Moreover, the thyroid gland also maintains body temperature by controlling the metabolic rate and energy production. Similarly, the increased organ functioning, metabolic rate, food conversion into energy ultimately results in the growth and development of a body [1].

Thyroid Hormones

There are three hormones produced by the thyroid gland namely thyroxine (T4), triiodothyronine (T3), and calcitonin. Thyroxine consist of the 4 atoms of iodine reacted with tyrosine (essential amino acid). However, the deficiency of iodine is more common as compared to tyrosine deficiency which is usually abundant in a body. When the T4 is deionized, it is converted into T3 which is the active form of the hormone that regulates and controls the thyroid mechanism. Calcitonin is responsible for stimulating calcium uptake from bones when it is required by the body [2].

What Is Hypothyroidism?

Hypothyroidism is the deficiency of T4 and T3 hormones that need to be considered. Such that the lower level of T3 reflects the low metabolism rate, irregulated organ functioning, and disturbed heart rate. This is because, T3 is the active element acquired by T4 de-iodination, that cannot be replaced by any other hormone [3].

Symptoms of Hypothyroidism

The most common symptoms of hypothyroidism include the following.

  1. Low energy and fatigue: Low energy and fatigue due to the lower T4 and T3 levels leading towards lower metabolic rate.
  2. Weight gain: Weight gain is observed in hypothyroidism patients because the fats and carbohydrates present in the consumed food, are not easily metabolized and absorbed into the body, hence resulting in accumulating in the body and weight gain [4].
  3. Cancer: There is an increased risk of several types of cancer because of the unregulated body organs and systems.
  4. Compromised immune system: Reduced functioning of the immune system is another symptom of hypothyroidism as the lack of T3 hormone leads to the ineffective functioning of the immune system [5].
  5. Low metabolism rate: Decreased metabolism is the result of hypothyroidism because the absence or lack of T3 leads towards a decreased metabolic rate.
  6. Slow growth: Slow growth is observed as a remarkable symptom of hypothyroidism, which is caused by the reduced metabolic rate in the absence of T4 and T3.

Symptoms of Iodine Deficiency

  1. Low energy and fatigue
  2. Weight gain
  3. Cancer
  4. Compromised immune system
  5. Low metabolism rate
  6. Slow growth

  As it can be cross-checked that the symptoms of hypothyroidism and iodine deficiency are the same, it reflects that hypothyroidism is the iodine deficiency and below the normal level of iodine is the reason for hypothyroidism [6].  

How Much Iodine is Required?

According to the New York Academy of Sciences, a healthy body requires 15-20 mg of iodine to prevent hypothyroidism as a reduced level of iodine can lead to poor body functioning. A healthy body required 15-20 mg of iodine in the body. It is important to notice that the iodine content present on the packaging of food items does not reflect its iodine in mg but it is written in micrograms (mcg) whereas 1mg = 1000 mcg. Being cautious while buying food items, one should remember that only 1000 mcg is equal to 1 mg which is a very small portion of iodine required for thyroid function. Here is a list of food items that contain iodine that should be included in the daily diet [7].

  1. Seaweed: 10 gms of seaweed contains 232 mcg of iodine therefore, it is the best source of iodine
  2. Bread made with iodized dough conditioner contain198 mcg of iodine, although this type of bread is no longer available in the market.
  3. Baked Cod is enriched with 158 mcg of iodine that can be used to be consumed organically.
  4. Greek, nonfat, and plain yogurt is another good source of iodine with 116 mcg of iodine.
  5. Oysters are also recommended to deal with iodine deficiency, as 1 cup of oyster contains 93 mcg of iodine.
  6. Nonfat milk: it is another source of iodine that can be included in the daily diet. 1 cup of nonfat milk contains 85 mcg of iodine.
  7. Iodized table salt: iodized table salt is considered to be enough to treat iodine deficiency but the case is different as it contains only 76 mcg of salt present in 1/4th teaspoon of the salt, which is much lesser than the required iodine [5].

How to Improve Thyroid Functioning

There are two ways through which thyroid functioning can be improved i.e. lab work and iodine supplements.

  1. Lab works are done to identify the iodine deficiency level so that the iodine supplements can be prescribed accordingly. This may include a blood test, iodine patch test, and urine test, among which the blood test is most accurate [3].
  2. Iodine supplements can be used to treat iodine deficiency which is the root cause of hypothyroidism. Iodine cannot be consumed directly as it can be toxic to the body. Therefore, iodine should be used in combination with different minerals such as zinc, selenium, magnesium, cortisol, B6, and others. The iodine supplements are available in different combinations with different minerals that are effective enough to improve iodine levels and to treat hypothyroidism [6].


  1. Persani L. Central hypothyroidism: pathogenic, diagnostic, and therapeutic challenges. The Journal of Clinical Endocrinology & Metabolism. 2012 Sep 1;97(9):3068-78. 
  2. Wiersinga WM. T4+ T3 combination therapy: any progress?. Endocrine. 2019 Oct;66(1):70-8.
  3. Ettleson MD, Bianco AC. Individualized therapy for hypothyroidism: is T4 enough for everyone?. The Journal of Clinical Endocrinology & Metabolism. 2020 Sep;105(9):e3090-104.
  4. Gurevitz S, Snyder J, Peterson K, Kelly K. Hypothyroidism and subclinical hypothyroidism in the older patient. The Consultant Pharmacist®. 2011 Sep 1;26(9):657-64.
  5. Markou K, Georgopoulos N, Kyriazopoulou V, Vagenakis AG. Iodine-induced hypothyroidism. Thyroid. 2001 May 1;11(5):501-10.
  6. Ikomi C, Cole CR, Vale E, Golekoh M, Khoury JC, Jones NH. Hypothyroidism and iodine deficiency in children on chronic parenteral nutrition. Pediatrics. 2018 Apr 1;141(4).
  7. Farebrother J, Zimmermann MB, Andersson M. Excess iodine intake: sources, assessment, and effects on thyroid function. Annals of the New York Academy of Sciences. 2019 Jun;1446(1):44-65.
  8. Farebrother J, Zimmermann MB, Andersson M. Excess iodine intake: sources, assessment, and effects on thyroid function. Annals of the New York Academy of Sciences. 2019 Jun;1446(1):44-65.

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