Health and Disease

Hypothyroidism: Possible Cause of Fatigue, Weight Gain, and Constant Coldness?

Approximately 5 in 100 people in the US, over the age of 12, suffer from hypothyroidism. This condition, more commonly known as an under-active thyroid, can cause unpleasant symptoms such as chronic fatigue which can make the daily lives of those affected significantly harder.


Approximately 5 in 100 people in the US, over the age of 12, suffer from hypothyroidism. This condition, more commonly known as an under-active thyroid, can cause unpleasant symptoms such as chronic fatigue which can make the daily lives of those affected significantly harder. Luckily, the disease can be easily treated but needs constant monitoring throughout one’s life to ensure that they have the correct dosage of medication


  • Excessive tiredness
  • Weight gain
  • Low mood
  • Constipation
  • Sensitivity to cold
  • Dry and scaly scalp
  • Brittle hair and nails
  • Slow movements and thoughts
  • Muscle aches and weaknesses

What is Hypothyroidism?

The thyroid gland is a butterfly-shaped organ in front of the trachea which controls the release of vital hormones. Your metabolism is controlled by this small organ and the hormones it releases allow the regulation of energy gained from food. The main hormones the thyroid is responsible for are triiodothyronine (T3) and thyroxine (T4) and fluctuations in these levels can cause symptoms of either hypothyroidism or hyperthyroidism (known as an overactive thyroid). If the thyroid gland doesn’t produce enough T3 or T4, you begin to experience the symptoms of an underactive thyroid which can result in constant tiredness, gain in weight, and a lower mood if not treated properly. 


An underactive thyroid can be present from birth, this is called congenital hypothyroidism, and all newborns in hospitals will be tested through the blood spot test at roughly 5 days old. Sometimes the immune system randomly attacks the thyroid gland, causing you to develop an underactive thyroid, and this common cause is known as Hashimoto’s disease. This disease causes hypothyroidism as a result of an autoimmune disorder, rather than direct damage to the gland, as it causes inflammation which prevents normal hormone function. 

Other causes of hypothyroidism can include damage to the thyroid during radiation treatment or surgery for a severely overactive thyroid, goiter, or thyroid cancer. During these procedures, excessive damage may be caused due to radiation attacking healthy cells as well as cancerous ones or a surgeon having to remove the whole organ as a result of other conditions. The treatment for hypothyroidism due to these causes is the same as that of Hashimoto’s and the symptoms can usually be easily treated using the right dose of hormone replacement. 

Finally, one other cause of hypothyroidism, albeit less common, is thyroiditis. Thyroiditis is a broad term that encapsulates any inflammation of the thyroid. Initially, thyroiditis can cause secretion of increased T3 and T4, leading to symptoms of overactive thyroid, which can last for the first 3 months after developing the condition. After this period, the thyroid may become underactive, which is usually temporary and only lasts a year- a year and a half, but occasionally is permanent. Thyroiditis can come on after childbirth (postpartum thyroiditis), due to a bacterial or viral infection (subacute thyroiditis), or painless, asymptomatic thyroiditis (“silent” thyroiditis). 


If you suspect you may be suffering from an underactive thyroid, it is important to speak to a family doctor so they can either perform diagnostic tests or refer you to a hospital’s endocrinology department if your case appears to be severe. Typically, the initial diagnosis of hypothyroidism can be made through a thyroid function test which is performed similarly to a classic blood test. This can show your medical team whether you have high levels of TSH (thyroid secreting hormone) and your T4 function. Once this test is performed, you can usually be treated by your local family doctor or GP but you may be referred to a specialist hormonal department (endocrinology) at a hospital if you are under 16, pregnant, or have underlying health issues that may affect treatment. 


Usually, an underactive thyroid is treated using oral hormone replacement tablets of levothyroxine. Most patients will have their TSH and T4 levels monitored at regular 3-month intervals to ensure you have the right dosage to effectively replace the lacking T3 and T4 hormones. Initially, you may be started on a low dosage (for example 25 micrograms) but if symptoms do not improve this can be adjusted, usually by going up by 25 micrograms or potentially 12.5 micrograms in children for a less dramatic increase. Once the correct dose is found, patients usually report an improvement in symptoms and only require monitoring on a yearly basis. However, it is important that if, after a while, your symptoms worsen to contact your doctor as this may indicate that your dosage is incorrect. 


Rarely, hypothyroidism can cause complications such as heart disease, goiter, pregnancy complications, and in extremely severe cases myxoedema coma. These complications typically only occur if a patient has suffered from a severely under-active thyroid, without treatment, over a long period of time. It is vital to contact a medical professional if you appear to be suffering from any of these complications and are experiencing classic symptoms of an under-active thyroid. 

Sophie Farr, Youth Medical Journal 2021


NHS England, “Underactive thyroid”, Accessed January 2021 from: 

US Department of Health and Human Science, “Hypothyroidism”, Accessed January 2021 from:

Endocrine Web, “Thyroid gland overview”, Accessed January 2021 from:,way%20your%20body%20uses%20energy.


By Sophie Farr

I am a student from the UK and my ambition is to become a doctor.

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