Hypothyroidism

Hypothyroidism refers to a deficiency of thyroid hormone due to its limited production by the body, which could be due to a multitude of factors. Thyroxine regulates several important bodily functions, such as heart rate, breathing, temperature, growth, calorie intake and metabolism, and disturbance in its levels leads to derangement of these functions. Hypothyroidism causes the metabolism to become sluggish, resulting in symptoms like fatigue, lethargy and weight gain.

There are three types of hypothyroidism:

1. Primary hypothyroidism

In primary hypothyroidism, thyroid gland cells are not able to produce sufficient quantities of the hormone due to an effect on the gland. A mild elevation in the levels of TSH is noted initially. Here is more about this type:

• Since the reduction in the levels of the thyroid hormone occurs due to an inability of the gland to synthesise enough hormone, the most common cause of primary hypothyroidism is the destruction of the gland due to a disease. The commonest cause of primary hypothyroidism is Hashimoto’s thyroiditis. It is an autoimmune disorder in which the immune system attacks healthy thyroid cells, thereby reducing their ability to produce the hormone. Hashimoto’s autoimmune thyroiditis can begin abruptly or may develop with time.
• Post-therapeutic hypothyroidism is another common cause, particularly after radioactive iodine therapy or surgery for goitre or hyperthyroidism.
• Other causes may be infectious diseases or congenital defects in the biosynthesis of thyroid hormone or deficiency of iodine.
• Iodine deficiency may also lead to congenital hypothyroidism, which can be a major cause of intellectual disability.
• Rare enzymatic defects can lead to impairment of thyroid hormone synthesis and cause hypothyroidism.

2. Secondary hypothyroidism

Secondary hypothyroidism occurs due to diseases of the hypothalamus that cause insufficient production of thyrotropin-releasing hormone(TRH) or diseases of the pituitary gland that cause an insufficient release of thyroid-stimulating hormone (TSH). This occurs due to limited stimulation of the thyroid gland to produce the hormone.

3. Subclinical hypothyroidism

In subclinical hypothyroidism, individuals show a rise in serum TSH levels, with minimal or absent symptoms of hypothyroidism and normal levels of serum-free thyroxine (T4). Subclinical thyroid dysfunction is common and is seen in those with Hashimoto’s thyroiditis. Such individuals are likely to develop overt hypothyroidism in the next 10 years, along with atherosclerosis and hypercholesterolaemia.

The symptoms and the advancement of the disease is gradable, that is, it can range from mild symptoms, which are barely recognised to life-threatening situations like a myxoedema coma. 

Symptoms of primary hypothyroidism

Symptoms of primary hypothyroidism often have a mild and insidious onset and involve several organ systems like:

• Metabolic: Intolerance to cold is a commonly noted symptom. Individuals are also likely to experience weight gain due to fluid retention. Hypothermia (low body temperature) is also seen in those affected.
• Skin-related: 
  Dermatological manifestations include puffiness of the face and oedema along with coarse and dry hair. The skin is also noted to be dry and scaly, but, it is thickened. In some individuals, wrinkles may also be seen. They may often have a dull and masked facial expression..
• Neurological: Patients with hypothyroidism often present with forgetfulness, slowing down of speech and an abnormal sensation in the hands and feet (paraesthesia). Some patients may present with carpal tunnel syndrome due to deposition of a proteinaceous substance in the ligaments around the wrist. Slowing of deep tendon reflexes is also observed.
• Psychiatric: Hypothyroidism may cause changes in personality, leading to depression, dementia or psychosis.  Reduced attention span, sleep apnoea and memory or calculative deficits may also be seen.
• Ocular: Individuals may present with swelling around the eyes and droopy eyelids due to the effort made to keep them open. The eyebrows also seem to be raised due to this effort.
• Cardiovascular and respiratory: Hypothyroidism is a major risk factor for the development of a variety of cardiovascular disorders due to an increase in cholesterol levels. A particular risk is for coronary heart disease. In some cases, pleural effusion (fluid in the pleural lining of lungs), hoarseness of voice may be seen.
• Gynaecological: Menstrual disorders occur in women with a severe form of the disease with. Secondary amenorrhoea or menorrhagia is then noted.

Symptoms of secondary hypothyroidism

In secondary hypothyroidism, the causes affect other organs that are under the control of the hypothalamic-pituitary axis.

• Dry hair and skin are symptoms of secondary hypothyroidism. Hypothyroidism can also interfere with the development of breasts and cause low blood pressure.
• Hypoglycaemia is commonly seen in such patients due to concomitant insufficiency of adrenal glands and growth hormone.

Myxoedemic coma

This is a life-threatening condition seen in patients with a long history of hypothyroidism. The main characteristics are hypothermia, loss of reflexes, seizures and decreased breathing. In a state of myxoedema coma, the individual often has a mask-like appearance of the face and barely responds when called. Sometimes, major signs of myxoedema coma like severe hypothermia can be missed if appropriate thermometers are not used. Rapid diagnosis is imperative, as the condition can be fatal without immediate treatment. 

Causes

There are many causes of hypothyroidism, such as:

• Hashimoto’s disease
  Hashimoto’s disease is the most common cause of hypothyroidism. It is an autoimmune condition in which the immune system attacks the thyroid gland, leading to inflammation and decreased production of thyroid hormone.
• Thyroiditis
  Thyroiditis causes the thyroid gland to become inactive leading to hypothyroidism which usually lasts for 18 months or may be permanent in some cases.
• Congenital hypothyroidism
  Babies may be born with an underdeveloped or malfunctioning thyroid gland. Untreated congenital hypothyroidism can lead to growth failure, delayed milestones and intellectual disability.
• Surgical removal of thyroid
  People who have had their gland surgically removed may develop hypothyroidism in the future. The gland may be removed as a treatment for goitre, hyperthyroidism, thyroid nodules or thyroid cancer.
• Radiation
  Radiation is a common treatment for hyperthyroidism, which gradually destroys thyroid cells. Patients receiving radiation therapy eventually develop hypothyroidism. Doctors may treat head and neck cancers with radiation, which may also lead to hypothyroidism.
• Medication
  Certain medicines like interferons, lithium and interleukins interfere with the production of TSH, leading to hypothyroidism.

Risk Factors

• Gender
  Women, especially older women, are at a greater risk of developing hypothyroidism.
• Autoimmune disorders
  Individuals with other autoimmune disorders like type 1 diabetes, multiple sclerosis, rheumatoid arthritis, coeliac disease, Addison’s disease, pernicious anaemia and vitiligo are at a greater risk of developing hypothyroidism due to the risk of Hashimoto’s disease.

Getting adequate amounts of iodine in the form of iodised salt is the most important step to prevent underactive thyroid disease. Some dietary supplements also contain iodine. However, it should be noted that iodine must only be consumed within recommended allowances, as an increased intake can lead to hyperthyroidism. The recommended intake of iodine for adults is about 150 micrograms per day. Children require lesser iodine than the amount recommended whereas pregnant and lactating women need more. It is imperative that you consult your doctor about the correct dosage of iodine in your diet.

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If the doctor suspects hypothyroidism, the following diagnostic steps are generally performed following a clinical examination and a detailed history of symptoms:

Thyroid profile
Serum TSH is the most sensitive test for the diagnosis of hypothyroidism. In primary hypothyroidism, serum TSH is elevated, with low levels of T4. In secondary hypothyroidism, serum TSH and T4 levels are low. Most individuals with hypothyroidism have normal levels of triiodothyronine (T3) and hence it is not very sensitive for the test.

Physical examination
An examination of the thyroid gland will be carried out to check for abnormal swellings or nodules in the area of the neck. Thyroid ultrasound may be ordered to check for inflammation or presence of nodules.

Hypothyroidism can be controlled, but cannot be completely cured. Here is the standard management protocol:

• Once the diagnosis of hypothyroidism is made, the doctor will prescribe a synthetic thyroid hormone which is to be taken daily. Thyroxine tablets are taken once a day, usually half an hour before breakfast so that the drug is absorbed better. The dose of thyroxine depends on the person’s body weight. Depending on the symptoms and thyroid hormone levels during follow-up, the dose can be adjusted every 2 to 3 months, as it may take that long to stabilise hormonal levels. Once the hormonal levels are stabilised, they may need to be checked only once a year.
• L-thyroxine can also be given in the form of salt supplements in order to enhance their absorption in the body.
• In some cases, combination therapy with T3 and T4 may be prescribed.
• If hypothyroidism is due to some other causes and underlying factors like Hashimoto's disease or other autoimmune disorders, these disorders are also managed accordingly.

If you are is receiving treatment for other conditions, it is best to inform your doctor, as the medication may interact with the synthetic thyroid hormone. Ensure that the doctor knows about any other supplements, including herbal supplements, that you may be taking.

Lifestyle management

Lifestyle modifications can greatly improve the functioning of the thyroid gland and help to manage the symptoms of hypothyroidism. These are:

• Healthy diet
  Since weight gain is one of the most common symptoms of hypothyroidism, it is imperative that you take care of your diet to keep this in check. Include an array of fresh vegetables, fruits, grains and lean protein in your diet. Stay away from sugars and saturated fats. A healthy diet helps in improving energy and maintaining a healthy weight. Also take care to avoid cruciferous vegetables like cabbage and cauliflower that can aggravate thyroid disease.
• Exercise
  A healthy exercise routine is another essential aspect of weight control. You can include your choice of exercise like aerobics, dance and pilates if you do not love to go to the gym. To begin with, 20 minutes of brisk walking every day on most days of the week, is sufficient to boost energy levels. Daily exercises also release good hormones known as endorphins that improve energy and mood and help in improving the quality of sleep. These benefits of exercise will help to manage problematic symptoms associated with hypothyroidism.
• Sleep
  Get adequate sleep. Aim for 7 to 8 hours each night. Adopt a regular sleep routine. The bedroom should be quiet and cool. Keep electronic gadgets and pets outside the room for sound sleep. Before sleep, engage in something relaxing like soothing music, meditation, a cup of green tea, a shower or light reading.
• Relieve stress
  It is noted that stress has a negative impact,which can worsen the symptoms of hypothyroidism. Even if the hypothyroidism is well under control, high stress can cause high amounts of cortisol and adrenaline to be released into the blood, leading to anxiety and tiredness, which worsens your sleep. The following steps are recommended to relieve stress:
  • Do something relaxing every day for at least ten minutes
  • Identify and avoid factors that can lead to stress
  • Yoga, exercise and meditation can help reduce the symptoms of hypothyroidism.

Prognosis

Hypothyroidism cannot be completely cured but is effectively managed. Most patients are managed appropriately, although many may require medications for life. Treating hypothyroidism with a regular dose of synthetic hormone is very effective, as the dose remains active in the body for a week and keeps T4 levels steady. If untreated, patients with severe hypothyroidism may develop a condition called myxoedema coma which is usually triggered by stress or traumatic injury. In contrast to other patients with hypothyroidism, myxoedema coma requires urgent hospitalisation and prompt treatment with injectable thyroid hormones. In children and babies, untreated hypothyroidism can lead to mental and growth retardation, which are preventable complications with appropriate treatment.

Complications

If left untreated, hypothyroidism can lead to the following conditions:

• Infertility
  Low levels of thyroid hormone can lead to infertility and amenorrhoea, that is the absence of a menstrual cycle. It may also cause a low sex drive and lack of interest in sex. Women may experience painful sex due to dryness of vagina. It may affect ovulation and decrease your chances of conceiving. Even with hormone replacement therapy, a successful conception cannot be guaranteed.
• Mental health
  Hypothyroidism can cause depression and, without treatment, the symptoms intensify and directly affect the mental state. In addition, untreated hypothyroidism is associated with a gradual decline in cognitive function and memory.
• Heart problems
  Even in the mildest form, hypothyroidism affects the heart. An underactive thyroid leads to an increase in levels of bad cholesterol. Elevated levels of cholesterol lead to its deposition in the arteries, thereby hardening them and causing atherosclerosis, which increases the risk of developing heart diseases and stroke. Hypothyroidism leads to fluid retention around the heart known as pericardial effusion, which may affect its functioning.
• Weight loss
  Thyroxine can lead to weight loss. People wanting to lose weight are tempted to take more thyroxine than required. This may lead to increased heart rate, tremors and irritability.
  
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• Goitre
  When thyroid gland overexerts itself to produce adequate quantities of thyroid hormone, enlargement of the thyroid gland can be caused due to overstimulation. This can be seen as a lump in the region of the neck and is termed as goitre.
• Birth defects
  Hypothyroidism in a pregnant woman can affect the developing foetus. If hypothyroidism is diagnosed during the first trimester, thyroid medications should be given to provide the developing baby with the desired levels of the hormone required for adequate mental growth. Babies born to women with untreated hypothyroidism may have severe developmental disorders and delayed milestones. However, if thyroid disorder is diagnosed and addressed soon after birth, healthy development is generally possible.