Last updated on October 13, 2021.
Hypothyroidism occurs when the thyroid gland produces a suboptimal amount of thyroid hormone, hence underactive, resulting in a lower rate of metabolism. Early symptoms of hypothyroidism are often neglected by patients as they are usually minor. Therefore, hypothyroidism is seldom clinically diagnosed in the early stage and may lead to fatal complications if untreated. Contrary to common belief, iodine deficiency is not the most common cause of hypothyroidism. Read more about circumventing hypothyroidism.
What is Hypothyroidism?
Hypothyroidism is the consequence of the lack of action of the thyroid gland, which is a butterfly-shaped endocrine gland at the lower front of the neck. It is usually characterized by inadequate thyroid hormone production, secretion and action. There are 2 major types of thyroid hormones, namely thyroxine (T4) and triiodothyronine (T3), to maintain normal body processes like energy production, sensation and body temperature regulation. In the case of hypothyroidism, cellular metabolism would be slowed down, giving rise to a series of signs and symptoms such as unexplained weight gain, slower pulse rate, loss of sensations, feeling cold, etc. It is particularly dangerous if myxoedema coma develops due to severe hypothyroidism and slow metabolism.
Causes of Hypothyroidism
Hypothyroidism is when the thyroid gland cannot serve the purpose of maintaining a normal level of thyroid hormones anymore, thus normal metabolisms are not attained. Contrary to popular belief, hypothyroidism is rarely caused by iodine deficiency, especially in developed areas like Hong Kong as iodine supply in food is usually ample. In fact, there are 3 types of reasons for hypothyroidism, primary (the inaction of the thyroid gland), central (the inaction of the central nervous system) and congenital (hypothyroidism acquired upon birth). More common causes of hypothyroidism include:
- Hashimoto’s disease: Hypothyroidism is most commonly induced by Hashimoto’s disease, which is a disease in one’s immune system resulting in it attacking the thyroid gland. As a result, the thyroid gland is inflamed and cannot produce substantial thyroid hormones like it used to.
- Congenital hypothyroidism: Due to genetic defects or some other unknown causes, some infants are born with hypothyroidism. Commonly, it is because of the absence or the underdevelopment of the thyroid gland. It leads to symptoms like excessive sleeping and jaundice. If left untreated, it may result in growth failure and intellectual disability in the future.
- Thyroiditis: Thyroiditis is the inflammation of the thyroid gland. Pain might not be felt accompanying the inflammation. Thyroiditis is usually induced after giving birth. Hashimoto’s disease is a kind of thyroiditis. It causes thyroid hormones to first leak out then run out of supply, thus leading to hypothyroidism.
- Lesions or radiotherapy of the thyroid gland: In accidents or surgery targeting hyperthyroidism, a part of or the entire thyroid gland is removed leading to the lack of action from the thyroid gland. Also, when the thyroid gland is under immense radiation to treat hyperthyroidism or cancers, the thyroid activity is heavily suppressed. It will be followed by hypothyroidism.
- Hypothyroidism-inducing medications: Some medications may cause hypothyroidism. For example, amiodarone, potassium iodide and nitroprusside may result in hypothyroidism.
Risk Factors of Hypothyroidism
The above causes will directly lead to hypothyroidism. However, there are some other habits or traits that, despite not directly causing hypothyroidism, increase the risk of hypothyroidism:
- Age: Those who are above 60 are more likely to suffer from hypothyroidism.
- Sex: Hypothyroidism occurs more likely in females.
- Medical history: Patients with type-1 diabetes, celiac disease are more likely to have hypothyroidism.
- Pregnancy: Women who have been pregnant or given birth to an infant within the last six months have a higher chance of hypothyroidism.
- Family history: If you have a family history of hypothyroidism, it is more likely for you to have hypothyroidism and you should pay more attention to your thyroid condition.
Signs and Symptoms of Hypothyroidism
The signs and symptoms of hypothyroidism, often associated with a lower metabolic rate, include:
- Weight gain
- Cold intolerance
- Coarse and dry hair
- Dry, rough pale skin
- Hoarse voice
- Hearing loss
- Memory loss
- Abnormal menstrual cycles
- Bradycardia (slow heart rate)
- Goitre (enlarged thyroid gland appears as a swelling at the neck)
- Myxoedema coma: It is a serious complication of hypothyroidism. When it happens, visit your physician immediately if you notice any of the following signs and symptoms:
– Hypothermia: Severe drop in body temperature
– Altered sensation: It may result in delirium and coma.
– Change of mental status
– Exaggerated signs and symptoms of hypothyroidism
Complications of Hypothyroidism
If hypothyroidism is neglected and untreated, various complications will ensue:
- Goitre: Goitre is the swelling of the neck due to an enlarged thyroid gland. It results from the continuously stimulated thyroid gland triggered by hypothyroidism. It will affect your appearance and occlude your oesophagus and respiratory tract, impeding swallowing and breathing.
- Issues ensuing pregnancy: For pregnant women, if hypothyroidism is untreated, it may lead to issues in both the fetus and the mother, including anemia in the mother, hypothyroidism in the fetus, birth defects or even miscarriage or stillbirth.
- Deteriorated mental health: Depression and poor mental functioning is the complication of hypothyroidism.
- Heart problems: As the metabolic rate is slowed down in hypothyroidism patients, “bad” cholesterol accumulates easily in them, increasing the chance of heart diseases like heart attack.
- Myxoedema coma: Untreated hypothyroidism rarely becomes extremely severe, resulting in myxoedema coma and is fatal. It has to be treated as soon as possible.
Diagnosis of Hypothyroidism
Upon detecting the signs and symptoms of hypothyroidism by physical examinations, other tests below should be done as soon as possible to confirm the presence of hypothyroidism and avoid its complications:
- Physical examination: The physician will check for the signs and symptoms of hypothyroidism like fatigue, dry skin, weight gain, constipation, etc, or review if you have a history of thyroid problems or goitre.
- Laboratory test: To confirm hypothyroidism, thyroid function test must be done by examining the blood levels of thyroid hormones. Hypothyroidism is indicated by the presence of a high thyroid-stimulating hormone (TSH) level, a low T4 level and a low T3 level. Thyroid antibody tests may be the follow-up procedure to confirm if hypothyroidism is caused by autoimmunity.
- Thyroid scan / Ultrasound: Imagings are used to examine the detail of the thyroid gland and see if it is underactive.
Treatments of Hypothyroidism
The treatments of hypothyroidism may include:
- Thyroid replacement therapy: Lifelong thyroid hormones supplementary drugs should be administered in the form of, commonly, levothyroxine or liothyronine. They can be used to resemble the action of thyroid hormones in your body to resolve hypothyroidism. Levothyroxine is more commonly used as it has a lower risk of causing hyperthyroidism, but it takes 4-8 weeks for you to see its effects.
- Supportive treatments: In the case of myxoedema coma, the situation is rather urgent. Therefore, supportive treatments should be incorporated as soon as possible to reverse the fatal situations by providing medications like glucocorticoids and antibiotics.
Hypothyroidism patients may consider taking food rich in selenium, including beef, beans, nuts, eggs and shellfish. If your hypothyroidism is not caused by your immune system, then you may also consider taking food rich in iodine, including seaweed, fish and eggs. Thyroid neck check may be carried out while facing a mirror. Thyroid gland is a butterfly-shaped gland at the lower front of the neck. Tilt your head back slowly while swallowing a sip of water. If there is an abnormal bulge around the lower front area, you might have an enlarged thyroid. For those with the risk factors mentioned above, regular self-check tests are recommended. Thyroid can affect the thickness and pattern of your period. It may make your menstrual cycle irregular or even stopped. When the thyroid hormone level is out of the normal range, prolactin release is affected correspondingly which alters one’s period and ovulation. Therefore, abnormalities will be observed in one’s period if the thyroid hormone levels are not right.
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Hypothyroidism patients may consider taking food rich in selenium, including beef, beans, nuts, eggs and shellfish. If your hypothyroidism is not caused by your immune system, then you may also consider taking food rich in iodine, including seaweed, fish and eggs.
Thyroid neck check may be carried out while facing a mirror. Thyroid gland is a butterfly-shaped gland at the lower front of the neck. Tilt your head back slowly while swallowing a sip of water. If there is an abnormal bulge around the lower front area, you might have an enlarged thyroid. For those with the risk factors mentioned above, regular self-check tests are recommended.
Thyroid can affect the thickness and pattern of your period. It may make your menstrual cycle irregular or even stopped. When the thyroid hormone level is out of the normal range, prolactin release is affected correspondingly which alters one’s period and ovulation. Therefore, abnormalities will be observed in one’s period if the thyroid hormone levels are not right.
*This article was medically reviewed by Dr. Gordon Chak Man Cheung from the London Medical Clinic, Central, Hong Kong. Dr. Cheung is a General Practitioner in HK who received his medical degree from King’s College London, University of London. Before completing his General Practice specialist training in UK, Dr. Cheung had worked in various hospitals in London and South East England in Cardiology, Endocrinology, Oncology, Paediatrics, Obstetrics and Gynaecology. He holds numerous postgraduate medical qualifications including Memberships to the Royal Colleges of Physicians in UK and to the Royal College of General Practitioners, Diploma of the Royal College of Obstetricians and Gynaecologists, Child Health as well as Clinical Dermatology.