What is the cause of the thyroid gland

Hypothyroidism: causes

An underactive thyroid can have various causes. There are both congenital and acquired forms of hypofunction.

Congenital hypothyroidism

The hypofunction is inherited or develops in the womb during pregnancy.

People with a congenital, initially undetected hypothyroidism usually suffer for a lifetime from the consequences of this defect, which almost never regress completely.

An underactive thyroid is based on the following undesirable developments:

  • The thyroid gland is present, but it does not produce any or too few hormones.
  • Thyroid gland is partially or completely absent (athyroidism).
  • Hormone production is disturbed by incorrect iodine utilization.
  • Target organs are insensitive to thyroid hormones.
  • Production of thyroid-stimulating hormone (TSH) by the pituitary gland is reduced.

On the other hand, a hypofunction developed during pregnancy can normalize completely. It has the following causes:

  • Iodine deficiency or increased iodine intake during pregnancy
  • Use of drugs during pregnancy that inhibit hyperthyroidism (anti-thyroid drugs).
  • Damage by the body's own immune system (autoimmune disease)

Acquired hypothyroidism

An underactive thyroid can also develop in the course of life. A family history may increase the risk of this.

It can be triggered by:

  • Inflammation of the thyroid gland, especially Hashimoto's thyroiditis
  • Thyroid surgery or after radiation therapy
  • Excessive or insufficient supply of iodine to the body (e.g. an underactive function can occur for a few weeks even after an excess of iodine)
  • Treatment of hyperfunction with hormone-inhibiting drugs (anti-thyroid drugs)
  • Disorders of the pituitary gland, which produces less TSH and controls the functions of the thyroid gland (so-called secondary, pituitary hypothyroidism)
  • Benign and malignant growths (tumors) in the thyroid gland after therapy
  • Antibodies from the own immune system that bind thyroid hormones and thus disrupt function
  • Insensitivity of the target organs to thyroid hormones

Hashimoto's thyroiditis

In addition to very rare acute forms of inflammation of the thyroid gland (due to viruses, bacteria), chronic inflammatory forms are also known. These are caused by a malfunctioning immune system. The best known is named after its discoverer, the Japanese doctor Hakaru Hashimoto (1881-1934), and mainly affects middle-aged women.

Normally the body's own defense substances protect against foreign bodies penetrating. In Hashimoto's thyroiditis, however, the antibodies are directed against the thyroid gland and trigger inflammation (thyroiditis). The glandular tissue is destroyed and replaced by connective tissue that is no longer hormonally active. As a result, too few hormones T4 and T3 are produced. As is the case with other autoimmune diseases, it is unknown why antibodies are formed against the tissue of the thyroid gland, and why it is damaged and even destroyed.