HYPOTHYROIDISM

What is the role of thyroid gland?

Thyroid gland is a butterfly shaped endocrine gland located in the neck. It produces thyroid hormones T3 and T4 and is controlled by TSH produced from another gland located in brain called pituitary gland.
Thyroid hormone helps in using energy, keep the body warm and maintaining the working of brain, heart, muscle and other organs in order.

Both excess (called as thyrotoxicosis) and deficiency of thyroid hormone (called as hypothyroidism) may be harmful and cause problems.

What is hypothyroidism?

Hypothyroidism means your thyroid gland is producing less thyroid hormone that required by your body. So you will have low FT3/Total T3 and FT4/Total T4 and high TSH.

Types of hypothyroidism

Depending upon the extent of increase or decrease in hormones it can be of two types.

1. Overt hypothyroidism – When TSH is very high or raised TSH is associated with low thyroid hormone levels.
2. Subclinical hypothyroidism – TSH is mildly raised with normal thyroid hormone levels.

What can cause hypothyroidism?

Hypothyroidism can occur due to following causes-

1. Autoimmunity (hashimoto’s thyroiditis) – This means antibodies are formed against thyroid gland and they destroy the cells producing thyroid hormone. So less thyroid hormone is formed. This type occurs more commonly in females.
2. Previous thyroid surgery like total or near total thyroidectomy (almost whole thyroid gland is removed) for any cause (thyroid cancer, hyperthyroidism, large goiter)
3. Previous radioiodine therapy for hyperthyroidism, thyroid or other cancers like hodgkin’s lymphoma
4. Congenital hypothyroidism– It may occur due to thyroid gland formation abnormalities, enzyme deficiencies or radiation exposure. Thyroid hormone is deficient since birth. So these patients can have severe neurological and developmental abnormalities if diagnosis gets delayed.
5. Thyroiditis– Thyroiditis means inflammation of thyroid gland due to any cause like viral infections, drugs, radiation, autoimmune etc. This can lead to temporary or permanent hypothyroidism.
6. Iodine deficiency – Iodine is an important mineral required for thyroid hormone synthesis. In some areas like sub-himalayan belt soil and water are deficient in iodine. So people may develop hypothyroidism.
7. Drugs– Some drugs can cause hypothyroidism like amiadarone, lithium, interferon alpha can cause hypothyroidism in people who are genetically predisposed or have antibody positivity.

What are the symptoms of hypothyroidism?

Due to low levels of thyroid hormone, metabolic processes of body slow down. So you have fatiguability, easy tiredness, cold intolerance, dryness of skin, hair fall, constipation, weight gain despite low appetite, sleepiness and depressed feeling may be present. Symptoms may be non-specific. In subclinical hypothyroidism, you may be asymptomatic.

How is hypothyroidism diagnosed?

1. Your doctor will take a detailed history regarding your symptoms, previous surgery or drugs, family history and conduct a detailed examination especially for thyroid swelling.
2. Blood test for FT3/Total T3, FT4/total T4 and TSH.
a. High TSH is the most sensitive test. In hypothyroidism, TSH is expected to be high except in secondary hypothyroidism ( which occurs due to low TSH).
b. Both T4 and T3 circulate in blood after binding to some proteins. Only small amounts are free from binding (called free T3 and free T4).
c. Total T3 and T4 measure both bound and unbound forms.
d. Usually free T3 and T4 testing is preferred. They can be low or normal.
3. Antibodies to thyroid gland ( Required for establishing the diagnosis and assess need for treatment in subclinical hypothyroidism).
4. Ultrasound neck if thyroid gland is enlarged or swollen.
5. Rarely, FNAC may be required if you have thyroid nodule or goiter (to rule out thyroid cancer).

Who should be tested for hypothyroidism?

You need to test your thyroid hormone levels if you have any one of the following-
1. If you are suffering from any autoimmune disease 
like type 1 diabetes (insulin dependent diabetes), Pernicious anaemia (low hemoglobin due to vitamin B12 deficiency caused by impaired absorption due to antibodies), celiac disease (Gluten allergy).
2. If you have a first degree relative (parents or siblings) with auto-immune thyroid disease
3. If you have a history of neck radiation to the thyroid gland including radioactive iodine therapy for hyperthyroidism and external beam radiotherapy for head and neck cancers
4. If you have prior history of thyroid surgery or dysfunction
5. If you have abnormal thyroid examination
6. If you are suffering from some psychiatric disorder (like depression)
7. If you are taking drugs like amiadarone or lithium
8. If you have any of these diseases like adrenal insufficiency, alopecia, anemia, cardiac arrhythmia, changes in skin texture, heart failure, constipation, dementia, dysmenorrhea (pain while menstruation), irregular periods, high cholesterol, high blood pressure, muscle weakness, vitiligo, weight gain.

What is the treatment of hypothyroidism?
Thyroid hormone replacement is the treatment for hypothyroidism.
Hypothyroidism may vary in severity, so your dose of levothyroxine may require a change.

Things to be careful for while you are on thyroid hormone replacement-

1. Take it empty stomach in the morning because absorption is best at that time (as soon as you get up in the morning).
2. Don’t take any other medicine especially iron/calcium tablets for at least 2-3 hours.
3. If you forget to take it in the morning some day, take it as soon as you remember. You can take 2 tablets together also if you have missed for 1 day.
4. Monitor your thyroid profile regularly.
5. Symptoms of overtreatment- fatigue, difficulty in getting sleep, increased appetite, tremors (shakiness), anxiety, palpitations (fast heart beat), increased sweating, heat intolerance, muscle weakness. So if on treatment you notice new symptoms, immediately get thyroid profile and consult your endocrinologist.

How to monitor in hypothyroidism?

1. Retest your thyroid profile after 6-8 weeks if thyroid hormone dose has been changed.
2. Once stable, then it can be checked every 6months to 1 year.
3. Earlier testing is required if-
a. Your symptoms have worsened.
b. You are gaining or losing weight fast.
c. You have changed your brand, timing of thyroid medicine
d. You have started other drugs like calcium, iron etc.
e. You have stopped taking medicine

When to consult an endocrinologist?

Most of the cases of hypothyroidism can be managed by general physicians well. But you may need to see an endocrinologist in following situations-
1. Children and infants having hypothyroidism
2. Difficult to maintain a euthyroid state 
(means you are having fluctuating TSH levels and requiring frequent dose change)
3. If you are pregnant or planning to become pregnant
4. If you are suffering from heart disease
5. If you have goiter ( neck swelling due to enlarged thyroid), thyroid nodule or structural 
changes in the thyroid gland
6. If you are suffering from other endocrine diseases like adrenal and pituitary disorders
7. Unusual combination of thyroid function test 
results 
example all the hormones TSH, T4 and T3 are either low or high
8. Unusual causes of hypothyroidism

Remember…

1. There is no cure for hypothyroidism. Most patients require lifelong treatment.
2. These hormonal tablets are exactly the same hormone as normally produced by thyroid gland, so it wont produce any side effects if proper dosage is taken.
3. If you feel you are stable, you can consult your doctor and he/she can try tapering off the medicine. But if your TSH rises again, then you should continue the same dose.