Thyroid Problems (cont.)
Thyroid Problems Causes
- Loss of thyroid tissue: Treatment of hyperthyroidism by
radioactive destruction of thyroid tissue or surgical removal of thyroid tissue can result in
- Antithyroid antibodies: These may be present in people who have
type 1 diabetes,
chronic hepatitis, or
Sjogren's syndrome. These antibodies may cause decreased production of thyroid hormones
because of thyroid destruction.
Hashimoto's thyroiditis, the most common cause of hypothyroidism in an adult, occurs because of autoimmune destruction of the thyroid results in a decreased production of thyroid hormone and an increased amount of TSH.
defects in the production of thyroid hormone: Hypothyroidism can be present from birth. This is commonly discovered early with nationwide
newborn screening for this disease.
When one of the steps in thyroid hormone synthesis is defective, the
production of thyroid hormone is reduced, with a subsequent increase in TSH. The increased TSH results in a
goiter (enlargement of the thyroid gland itself that can be seen as an obvious swelling in the front of the neck).
If the metabolic block is severe, thyroid hormone levels are low begining at
birth, resulting in mental retardation, goiter, and short stature
- Medications: Some medications, particularly
Lithobid), may cause a drug-induced hypothyroidism.
- Graves' disease: This autoimmune thyroid condition results from
abnormal stimulation of the thyroid gland by a material in the blood termed
the thyroid stimulating immunoglobulin (TSI). TSI overstimulates the thyroid
causing a goiter. It also causes Grave's eye disease, including a "bug-eyed"
look and "frightened stare." This can progress to severe eye pain or eye
muscle weakness causing tearing and double vision. In severe cases, the
swelling of the eye and surrounding tissue can cause loss of vision. It also causes raised, thickened skin over the shins or tops of the feet.
- Toxic multinodular goiter: This occurs when a nodule in the thyroid gland produces thyroid hormones all by itself, without regard
to the degree of TSH stimulation. It usually occurs in people with a long-standing goiter, usually in the elderly. Toxic multinodular goiter is different from Graves' disease because of the general lack of eye
complications and less severe signs of hyperthyroidism.
- Subacute thyroiditis: This temporary inflammatory disorder of the
thyroid gland includes such conditions as de Quervain's thyroiditis or
postpartum subacute thyroiditis. In these conditions, there may be periods of
increased thyroid hormone release due to the inflammation, causing excess thyroid hormone to be released. After the all the thyroid hormone has leaked out of the damaged tissue, a temporary hypothyroid period begins and can last 2-4 months. Usually 90% of people with this condition will go back to normal thyroid function without treatment.
- Pituitary adenoma:
This tumor of the pituitary gland causes independent TSH production leading to overstimulation of the thyroid gland.
- Drug-induced hyperthyroidism: This is most commonly
caused the the heart medication amiodarone (Cordarone).
Goiter or Nodules Causes
- Most of the time
thyroid nodules and thyroid goiters do not cause any
symptoms. Some goiters are found because of the thyroid hormone
overproduction or underproduction from the thyroid gland. Some nodules are
found because a patient or doctor sees or feels a lump in the neck. If the goiter becomes very large,
the person may feel a pressure in the front of the neck with swallowing hard or firm foods such as bread crusts or meat. This pressure may also cause a small
dry chronic cough. It is rare that the thyroid can become large enough to completely block swallowing or breathing.
- Nodular or multinodular goiter: This is a condition in which multiple
nodules form in the thyroid. There are only two conditions that cause
thyroid enlargement and nodules: 1) external radiation exposure, or 2) iodine
deficiency. Often several members of a family.
will have an enlarged goiter as the condition can be inherited
- Thyroid cancer: There are several types of thyroid cancer. The most
common type, papillary thyroid carcinoma, occurs in more than 85% of cases.
This type of cancer can be caused by radiation exposure as a child or
adolescent, including therapeutic radiation used in the treatment of cancers
or in accidents such as the Chernobyl nuclear disaster. Most of the time,
the reason for developing thyroid cancer is unknown.
Stephanie L Lee, MD, PhD, FACE
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