Thyroid Problems Overview
by Anatomy in Motion.
The thyroid gland is located on the front part of the neck below the thyroid cartilage (Adam's apple). The gland produces thyroid hormones, which regulate metabolic rate (how fast calories are consumed to produce energy). Thyroid hormones are important in regulating body energy, body temperature, the body's use of other hormones and vitamins, and the growth and maturation of body tissues.
Diseases of the thyroid gland can result in either production of too much (overactive thyroid disease or hyperthyroidism), too little (underactive thyroid disease or hypothyroidism) thyroid hormone, thyroid nodules, and/or goiter. Thyroid problems are much more common in women than in men.
Production of thyroid hormones: The process of hormone synthesis begins in a part of the brain called the hypothalamus. The hypothalamus releases thyrotropin-releasing hormone (TRH). The TRH travels through the venous plexus located in the pituitary stalk to the pituitary gland, also in the brain. In response, the pituitary gland then releases thyroid-stimulating hormone (TSH, also called thyrotropin) into the blood. The TSH travels to the thyroid gland and stimulates the thyroid to produce the two thyroid hormones, L-thyroxine (T4) and triiodothyronine (T3). The thyroid gland also needs adequate amounts of dietary iodine to be able to produce T4 and T3, the molecules of which contain four and three atoms of iodine, respectively.
Regulation of thyroid hormone production: To prevent the overproduction or underproduction of thyroid hormones, the pituitary gland senses how much hormone is in the blood and adjust the production of hormones accordingly. For example, when there is too much thyroid hormone in the blood, TRH and TSH production are both decreased. The sum effect of this is to decrease the amount of TSH released from the pituitary gland and to reduce production of thyroid hormones from the thyroid gland to restore the amount of thyroid hormone in the blood to normal. Defects in these regulatory pathways rarely may result in hypothyroidism (underactive thyroid problem) or hyperthyroidism (overactive thyroid problem). The most common cause of hypothyroidism and hyperthyroidism occurs due to problems within the thyroid and not the regulatory system.
Thyroid goiter: Thyroid goiter is any enlargement of the thyroid that can occur with hyperthyroidism or hypothyroidism but also with benign and malignant (cancerous) nodules. Worldwide, the most common cause of goiter is iodine deficiency. Although it used to be very common in the U.S., it is now less common with the use of iodized salt. Multiple nodules in the thyroid are very common, but only about 5% of the nodules are a thyroid cancer. Thyroid cancer rates have been increasing steadily by about 6% every year for more than 20 years. It is one of the few cancers whose rate is increasing and whose very low rate of mortality is also rising with time. Although radiation exposure as a child can increase the risk of thyroid cancer, we do not know why the overall rate has been increasing. Thyroid cancer is diagnosed after a thyroid ultrasound exam and a needle aspiration biopsy of the nodule.
Hypothyroidism Causes
Loss of thyroid tissue: Treatment of hyperthyroidism by radioactive destruction of thyroid tissue or surgical removal of thyroid tissue can result in hypothyroidism.
Antithyroid antibodies: These may be present in people who have type 1 diabetes, lupus, rheumatoid arthritis, 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.
Congenital 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 (hypothyroid cretinsim).
Medications: Some medications, particularly lithium (Eskalith, Lithobid), may cause a drug-induced hypothyroidism.
Hyperthyroidism Causes
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.
Hypothyroidism (Low Thyroid Hormone Level) Signs and Symptoms
Symptoms of hypothyroidism in infants can include:
• Constipation
• Poor feeding
• Poor growth
• Jaundice (yellow discoloration of the skin and eyes)
• Excessive sleeping
Symptoms of hypothyroidism in children include:
• Excessive fatigue
• Poor growth
• Delayed tooth development
• Delayed sexual maturation
• Poor school performance
Symptoms of hypothyroidism in adults include:
Early symptoms
• Easy fatigue, exhaustion
• Poor tolerance to cold temperatures
• Constipation
• Carpal tunnel syndrome (pain at the wrists and numbness of the hands)
Later symptoms
• Poor appetite
• Weight gain
• Dry skin
• Hair loss
• Intellectual ability worsens
• Deeper, hoarse voice
• Puffiness around the eyes
• Depression
• Irregular menstrual periods or lack of menstrual periods
Original Article and MUCH more info here: http://www.emedicinehealth.com/
