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Thyroid Diseases

Thyroid diseases are caused by abnormal functions of the thyroid gland which produces two main hormones, thyroxine (T4) and triiodothyronine (T3) to control metabolism and another hormone, calcitonin, to regulate the amount of calcium in the blood. Thyroid diseases occur when these hormones are either under-produced or overproduced.

Hypothyroidism

Hypothyroidism is a condition in which insufficient thyroid hormones are produced. Possible causes include:

Autoimmune disease
In a disease called Hashimoto's thyroiditis, the immune system produces antibodies that attack the thyroid gland, reducing its ability to produce hormones.

Iodine deficiency
Iodine is necessary for the production of the hormones T3 and T4 because these molecules contain iodine. If there is an iodine deficiency, the thyroid cannot make sufficient hormone.

Pregnancy
About 5-10 percent of women develop hypothyroidism during or after pregnancy. This condition is called postpartum hypothyroidism.

Medical treatment
Some medical treatment, such as thyroid surgery, radiation therapy or drugs, may impair the functions of the thyroid.

Symptoms
  • Sensitive to cold
  • Weight gain
  • Fatigue
  • Hoarse voice
  • Dry, pale skin
  • Frequent menstrual periods
Diagnosis

Hypothyroidism can be diagnosed by blood tests that measure the amount of thyroid-stimulating hormone (TSH) and thyroxine (T4). If TSH is high but thyroxine is low, it indicates that the thyroid is underactive.

Treatment

Doctors may prescribe a synthetic hormone (e.g., levothyroxine) to replace missing thyroid hormone in the body.

Hyperthyroidism

Hyperthyroidism is a condition in which excess thyroid hormones are produced. Possible causes include:

Graves' disease
This is an autoimmune disease in which the immune system makes antibodies that stimulate excessive production of hormones T4 and T3. Graves' disease is the most common form of hyperthyroidism.

Overactive nodules (toxic adenoma)
The thyroid nodules are overactive, producing excessive amount of hormones T4 and T3.

Thyroiditis
Inflammation of the thyroid may result in excess release of hormones stored in the thyroid gland. This happens in subacute thyroiditis and postpartum thyroiditis. In both disorders, hyperthyroidism is followed by hypothyroidism.

Symptoms
  • Irritability, nervousness, or anxiety
  • Rapid heartbeat
  • Enlarged thyroid gland
  • Tremor
  • Hard to sleep
  • Infrequent menstrual periods
  • Weight loss
  • Sensitive to heat
Diagnosis

Hyperthyroidism can be diagnosed by blood tests that measure the amount of thyroid-stimulating hormone (TSH) and thyroxine (T4). If TSH is low but thyroxine is high, it indicates that the thyroid is overactive.

Treatment

There are several treatment options for hyperthyroidism:

Radioactive iodine - The drug may be taken by mouth. Active cells of the thyroid gland will be destroyed after picking up the drug.

Anti-thyroid medications - This type of drugs, such as methimazole or propylthiouracil, can inhibit the production of thyroid hormones.

Surgery -  To remove part of the thyroid gland.