What is the function of the thyroid?

The thyroid is a four-to-five inch gland that sits in the neck below the Adam’s apple. Its main function is to make thyroid hormone, which helps to regulate overall metabolism. Thyroid hormone functions like the “thermostat” of the body, helping to regulate temperature, heart rate, bowel function, energy, and overall feeling of well-being.

What is hypothyroidism?

Hypothyroidism is a condition in which the thyroid is not producing enough thyroid hormone that the body requires.

What are the causes of hypothyroidism?

The most common cause is an autoimmune destruction of the thyroid gland called Hashimoto's Thyroiditis, a condition in which the body’s own immune system (white blood cells) attacks the thyroid-causing dysfunction. It can happen at anytime and often does not have a triggering factor. Sometimes it can occur after pregnancy, though this is often only temporary. The predisposition to develop hypothyroidism is often inherited as are many other autoimmune diseases.

Hypothyroidism can also result from surgical removal of the thyroid gland, which is sometimes done due to enlargement of the gland or nodules that develop within it.

Radioiodine treatment given for the treatment of hyperthyroidism (overactive thyroid) can also cause permanent hypothyroidism, resulting in a life-long requirement for thyroid supplementation.

What are the symptoms of hypothyroidism?

Common symptoms include:

  • Fatigue
  • Weight gain
  • Cold intolerance
  • Constipation
  • Decreased concentration
  • Hair loss
  • Muscle aches
  • Heavier or irregular menstrual periods
  • Depression

How is hypothyroidism diagnosed?

Hypothyroidism is diagnosed by a simple blood test. The best blood test to screen for hypothyroidism is the measurement of thyroid stimulating hormone (TSH) levels. In general, if TSH is in the normal range, the thyroid is functioning properly.

TSH is made by the pituitary gland, the “master gland” of the body that is in charge of regulating the thyroid gland. If the TSH level is high, the thyroid is not adequately meeting the needs of the body—in other words, it is not making enough thyroid hormone, indicating an underactive thyroid gland.

Thyroid autoantibodies also can be measured via a blood test and can help identify people who are at increased risk for developing thyroid disease.

How is hypothyroidism treated?

The treatment for hypothyroidism is taking supplements. Thyroid hormone supplementation has been around for many decades. It is safe when given at appropriate doses and should be monitored with periodic blood testing. Another safe and effective treatment is with levothyroxine, which is a synthetic form of the predominant thyroid hormone T4.

Levothyroxine comes in the form of a small tablet that is taken once daily. Ideally, it is taken on an empty stomach in the morning, 30-to-60 minutes prior to breakfast. It should not be taken with vitamins, iron or calcium, which can interfere with its absorption; these supplements should be taken four hours apart from thyroid hormone.

How is hypothyroidism monitored?

Once a patient is started on thyroid hormone, a TSH is checked every two-to-three months. Based on the level, the dose may be adjusted to maintain a normal TSH (goal of between one and three for most individuals). Once this level has been reached and has been stable, depending on the individual, the TSH can be checked every 6-12 months thereafter. It is important to avoid overtreatment because this can potentially cause bone loss and heart arrhythmia. Your doctor will tell you how often your levels should be checked.

It is especially important to monitor levels prior to and during pregnancy to ensure that the fetus receives adequate levels of thyroid hormone needed for growth and development.