This article starts below.

Thyroid hormones are essential for the body to function normally. To achieve this purpose, the thyroid hormones must be present in the body in the correct amount -- not too little and not too much.

Hypothyroidism often results as a failure or inability of the thyroid gland to produce adequate amounts of thyroid hormones. Too little thyroid hormone causes the body to “slow down.”

What are the causes of hypothyroidism?

Autoimmune thyroiditis (Hashimoto's thyroiditis) occurs when the body's immune system produces a reaction in the thyroid gland that results in hypothyroidism. Other autoimmune diseases may be associated with this disorder, and family members may also be affected.

Radioactive iodine treatment may cause hypothyroidism after its use for treatment of hyperthyroidism.

Thyroid operation can cause hypothyroidism, especially if most of the thyroid has been removed.

Thyroiditis, or the inflammation of the thyroid gland, may cause hypothyroidism after a period of hyperthyroidism.

Postpartum thyroiditis may cause hyperthyroidism followed by hypothyroidism shortly after pregnancy.

Congenital conditions may cause infants to have an inadequate amount of thyroid tissue or an enzyme defect that does not allow normal thyroid hormone production. If this condition is not treated promptly, physical stunting and mental damage (cretinism) may develop.

What are the common symptoms of hypothyroidism?

Hypothyroidism is usually present and may be associated with some or all of the following symptoms:

  • intolerance to cold
  • weight gain
  • constipation
  • low fertility
  • depression
  • sleepiness
  • forgetfulness
  • puffy face
  • falling hair
  • muscle weakness
  • fatigue
  • dry skin
  • longer or heavier menstrual blood flow

How is hypothyroidism diagnosed?

Hypothyroidism is diagnosed with blood tests like thyroid stimulating hormone (TSH), tri-iodothyronine (T3) or tetra-iodothyronine (T4) levels. A high TSH level is the most accurate indicator of hypothyroidism. If the TSH level is high, it is very important to check thyroid hormone levels (low T3 and T4) to confirm the diagnosis of hypothyroidism.

Radioactive iodine uptake may also be used to diagnose hypothyroidism. It is a measurement of how much iodine the thyroid gland can collect. A thyroid scan shows how the iodine is distributed throughout the thyroid gland. This information can be useful in determining the cause of hypothyroidism.

How is hypothyroidism treated?

Hypothyroidism is treated by giving thyroid hormone pills, oftentimes taken for life. It is very important to remember that thyroid hormone pills should be taken on an empty stomach. The aim of treatment is to normalize the TSH. The appropriate dose is individualized, based on periodic blood level testing of thyroid hormones.

Excerpt from The Thyroid Gland: Hypothyroidism by the Philippine Society of Endocrinology and Metabolism.