The thyroid gland is a small organ in the body located in the lower front portion of the neck in the shape of a butterfly. It is in charge of producing thyroid hormones, namely triiodothyronine (T3) and thyroxine (T4), which regulates how the body stores and uses energy.

Hypothyroidism occurs when the body does not make enough thyroid hormones. Hypo- refers to low or below normal, and should be distinguished from Hyperthyroidism where there is excess thyroid hormone being produced in the body.

Signs and Symptoms

The clinical presentation of signs and symptoms experienced by an individual who has hypothyroidism varies according to the severity of hormone deficiency and how fast this lack develops. Hypothyroidism will affect various parts of the body due to the wide range of normal function of the hormone on the body. Some of these signs and symptoms include:

• Fatigue and sluggishness
• Weight gain
• Intolerance to the cold
• Reduced sweating and dry skin
• Mild facial swelling
• Slowed heart rate and reduced heart function – leads to shortness of breath with exercise
• Weakened respiratory muscles – leads to shortness of breath with exercise
• Irregular menstruation which ranges from absent, infrequent to heavy periods – leads to difficulty in conceiving
• Increased risk of miscarriage during pregnancy

The manifestation of these signs and symptoms are due to the general slowing down of the body’s metabolism and loss of regulation of components in and out of the blood vessels.

Causes of Hypothyroidism

Most cases of hypothyroidism are primary hypothyroidism, where there is a direct issue with the thyroid gland which leads to a reduced production of thyroid hormones.  These may include, but are not limited to:

• Autoimmune thyroiditis (Hashimoto’s thyroiditis). The body’s immune system develops antibodies that start to attack the thyroid gland and destroy thyroid tissues.
• Surgical removal of the thyroid gland to treat hyperthyroidism. Hypothyroidism in these cases may be delayed from weeks to months depending on the extent of removal and other factors.
• Radioactive iodine treatment, to destroy thyroid tissues in hyperthyroidism. Depending on the condition of the individual prior to treatment, some may experience hypothyroidism right after treatment while some weeks to years later.
• Iodine intake. Iodine is a nutrient which is involved in the production of thyroid hormone. Inadequate consumption of iodine in the daily diet can lead to iodine insufficiency and consequently reduced production of thyroid hormone leading to hypothyroidism. Conversely, iodine excess may cause hypothyroidism in individuals who have autoimmune thyroiditis. The normal recommended daily intake of iodine is less than 100mcg/day.
• Medication. Various medications may cause a reduction in thyroid hormone production. Hyperthyroid medications such as Propylthiouracil (PTU) and Methimazole. There are other medications which may also potentially cause a decrease in thyroid hormones.

On the other hand, the production of thyroid hormones are also regulated by a cascade of other hormones such as the Thyroid-stimulating Hormone (TSH) from the brain. Any disturbance to the organs (the hypothalamus and pituitary glands) producing these hormones along the pathway before reaching the thyroid will affect the feedback mechanisms. This will lead to secondary or tertiary hypothyroidism. 

Diagnosis

Hyperthyroidism can be detected at early stages before it progresses.

When there are signs and symptoms suggestive of hypothyroidism as discussed, or any thyroid abnormalities, blood tests can be performed to diagnose it (Find doctor). Blood tests are able to identify the underlying cause of hypothyroidism and redirect specific treatment plans. The most common test would be to measure the level of Thyroid-stimulating hormone (TSH) in the body. TSH is the most sensitive test as it is able to detect small changes in thyroid functions. Thyroxine (T4) may also be tested to assess the degree of hypothyroidism.

Routine screening is done in all newborn babies in Malaysia. Blood from the placenta cord is routinely taken right after birth to test for any presence of thyroid hormone deficiency. If for any reason cord blood is not available, blood samples from the veins can be taken after the third day of life for more accurate results.

Treatment

The main aim of treatment in hypothyroid patients is to normalise the thyroid-stimulating hormone (TSH) and thyroxine (T4) levels in the blood, and to alleviate symptoms experienced.

Thyroid hormone replacement therapy is a common treatment where an oral form of T4 hormone is to be taken once a day. Frequent monitoring of the hormone levels is required to determine the effectiveness of treatment. Strict compliance is needed and any change in dosages should be under the advice and evaluation by a physician to ensure full benefits and to reduce the risk of adverse effects.

It is important to note that treatment options will vary according to individual conditions and the circumstances which led to the development of hypothyroidism. Evaluation and treatment plans should be fully discussed and explained by the appropriate trained healthcare professional teams to ensure full understanding and best treatment outcome.