Hypothyroidism is a condition where the thyroid gland is unable to produce normal levels of the thyroid hormone. Doctors sometimes call it an ‘underactive thyroid’. It is a fairly common condition and it is one of the most easy-to-manage conditions that I see in clinical practice.
Hypothyroidism is commonly seen in women, individuals over the age of 65 years and sometimes patients who have coeliac disease and type I diabetes mellitus. Interestingly, individuals who smoke tobacco and consume alcohol in moderate amounts are associated with a lower risk of developing hypothyroidism.
Is hypothyroidism hereditary?
Studies have found that hypothyroidism can be hereditary in up to 65% of patients. This means that if someone in the family has got hypothyroidism, there is a 6 out of 10 chance of developing the condition. There are of course conditions where infants have hypothyroidism at birth, but I will not discuss this as it is not relevant to the current topic.
Types of hypothyroidism
There are different types of hypothyroidism. In primary hypothyroidism, the thyroid gland itself is unable to produce thyroid hormone. In secondary hypothyroidism, the brain fails to produce thyroid stimulating hormone i.e. TSH. There are other forms of hypothyroidism such as tertiary hypothyroidism and peripheral hypothyroidism.
Symptoms of hypothyroidism
Most patients who have hypothyroidism do not present any symptoms. It is often found on routine clinical testing and in most cases, requires close follow-up of the thyroid stimulating hormone and free T4 levels. That being said, the most common symptoms of hypothyroidism have been listed in the image below.
As you can see, the symptoms are fairly not non-specific and it is difficult to tell just from someone having tiredness or weight gain that they truly have hypothyroidism.
However, one must bear in mind that hypothyroidism that is not treated can affect most vital structures, particularly the cardiovascular system. An underactive thyroid gland has been associated with reduced heart function, breathlessness and a drop in blood pressure. Some individuals can develop injury to the heart and fluid accumulation around the heart muscle as well.
Hypothyroidism also has effects on the metabolic aspect of the human body, meaning it increases total cholesterol levels and LDL levels as well. Serum homocysteine levels can also be elevated. It can also affect the nervous system leading to alteration in taste, vision and hearing. Patients who have very bad hypothyroidism can have hoarseness of voice and alteration in hearing.
Impaired cognitive function, loss of memory and dementia, depression and compression of nerves in various aspects of the body (for example carpal tunnel syndrome) have also been described. Patients may also develop constipation, anaemia, change in the texture of the skin, loss of eyebrows, hair loss, yellow discoloration of the hands and low sodium levels.
As you can see, it is not a condition to be ignored and must be treated appropriately.
What happens if hypothyroidism is not treated?
If the degree of hypothyroidism is mild, it can be managed with watchful waiting and close observation of the TSH and free T4 levels. However, in patients who have TSH levels above 10 mIU per litre, there has been an association with weakening of the heart and a higher risk of cardiac problems, especially if patients are undergoing procedures such as coronary angioplasty.
In some patients in whom the TSH levels are extremely high and hypothyroidism remains untreated, a life-threatening condition called myxoedema coma may ensue.
Tests for hypothyroidism
It is fairly easy to diagnose hypothyroidism. A simple blood test checking TSH levels and free T4 levels is often sufficient. Routine measurement of T3, T4 and freeT3 levels is not normally necessary. In patients in whom hypothyroidism is suspected, the measurement of anti-thyroid peroxidase antibodies is sometimes done to help confirm the diagnosis. A thyroid ultrasound scan may sometimes also be helpful.
Who should be screened for hypothyroidism?
The recommendations from the American Thyroid Association is that all individuals over the age of 35 years should get their thyroid function checked every five years. This is especially important for women. Individuals over the age of 60 years must have their thyroid function test done periodically as per the physician’s advice.
Individuals who have extremely high cholesterol levels, dementia and a family history of hypothyroidism, and those individuals who take medication such as lithium, should also have their thyroid function test done from time to time.
Treatment of hypothyroidism
The primary treatment of hypothyroidism is supplementation with levothyroxine which is an oral form of the thyroid hormone. The starting dose ranges from 12.5 µg once a day on empty stomach to be taken one hour before food. In individuals who have coronary artery disease, starting dose can be up to 25 µg per day.
The recommended treatment dosage for patients with hypothyroidism and its associated symptoms is 1.5 to 1.8 µg per kilogram bodyweight. With constant and close monitoring of the thyroid function, it is possible to titrate and change the dose over a period of three months until the right dose is reached.
It is important that the dose is titrated correctly as over-treatment can have side-effects such as bone thinning and irregular heart rhythms (atrial fibrillation). If under treated, patients can have continuing symptoms and signs and may be at a higher risk of developing heart disease.
Treatment Failure
In some individuals, the TSH levels remain elevated despite medication. This may be due to a number of reasons such as inadequate dosing, intake of tablets with food and interactions of thyroid medication with certain commonly used medicine such as antacids, calcium tablets, hormone supplement therapies, anti-epilepsy medicines and anti-TB drugs.
Of course, some people are non-compliant with medicines and do not take the tablets on a regular basis and this can lead to inadequate treatment. Individuals who have stomach issues such as Helicobacter infection, coeliac disease, diabetes related stomach disease and anaemia may also remain inadequately treated.
How and when to take thyroid medication?
Thyroid medication is absorbed from the small intestine and is advised to be taken early morning 30 to 60 minutes before breakfast on an empty stomach. The medicine can also be taken 3 hours after the last meal of the day prior to going to bed. It is strongly advised against taking thyroid medication along with or after food as it does not break down appropriately and hence will not treat the condition.
Hypothyroidism is a very common condition. Fortunately, it is easy to treat. However, if left untreated, it can lead to problems. Speak with your doctor today about thyroid disease.