The Thyroid
  The thyroid gland is located in the lower neck, above the breastbone on either side of the windpipe. Its function is to provide the body with thyroid hormones, chemicals that are essential for the normal function of each cell organ in the body

Thyroid pathology is very common. One in five people will develop a thyroid lump which needs medical attention. More than 20 million people in the US have an overactive or underactive thyroid, but half of them do not even know they have the disease. Even among those who know they have a thyroid condition, many are taking either too much or too little medication.

Thyroid problems manifest themselves as abnormalities of function or structure.

Structure abnormalities consist of goiter (an enlarged thyroid gland), and nodules or lumps. To rule out cancer, a thyroid fine needle aspiration is required (biopsy).

Function abnormalities comprise an overactive or an underactive thyroid. Both cause a variety of symptoms involving virtually every organ of the body, hence the difficulty in diagnosing the thyroid condition.

Thyroidology, the science of the thyroid, has undergone rapid development in the last years. For example, subclinical over- and underactive thyroid has been recently associated with bone loss, high cholesterol, heart problems, etc. Previously normal TSH levels are now under scrutiny.

Thyroid Symptoms
Symptoms suggestive of thyroid disease are:
  • weight loss
  • tremors
  • palpitations
  • nervousness
  • frequent bowel movements
  • tiredness
  • irregular menstrual periods
  • lump in the neck
  • enlargement of the thyroid gland
  • history of neck irradiation in childhood or adolescence (high risk of thyroid cancer),
  • history of a thyroid problem in the past
In addition, you are at high risk of having a thyroid problem if you
  • have any close relatives with  a history of thyroid disease
  • take insulin for diabetes
  • need vitamin B12 shots for anemia
  • have premature gray hair
  • have white skin patches (known as vitiligo)
The most common thyroid disorder is an underactive thyroid, or hypothyroidism. This results when the thyroid fails to produce enough hormone. Less frequently, an overactive thyroid condition, or hyperthyroidism, occurs when the thyroid produces more thyroid hormone than is needed. If properly treated, patients with thyroid disorders lead normal, active lives. When left untreated, however, thyroid disorders can affect the patient's cardiovascular system, reproductive system and other major organs.

How the Thyroid Functions
The thyroid gland operates as part of a feedback mechanism involving the hypothalamus and the pituitary gland. First, the hypothalamus sends a signal to the pituitary gland through a hormone called TRH (thyrotropin releasing hormone). When the pituitary gland receives this signal, it releases TSH (thyroid stimulating hormone) to the thyroid gland. Upon receiving TSH, the thyroid responds by releasing two of its own hormones, T4 and T3, which then enter the bloodstream and affect the metabolism of the heart, liver, muscle and other organs. T4 is the main hormone released by the thyroid. T3 is made in the tissue after T4 to T3 conversion. Finally, the pituitary "monitors" the level of thyroid hormone in the blood and increases or decreases the amount of TSH released, which then changes the amount of thyroid hormone in the blood.

The most common type of thyroid disorder, hypothyroidism (underactive thyroid) occurs when the thyroid gland fails to produce enough thyroid hormone -- hormones which influence essentially every organ, every tissue and every cell in the body. Hypothyroidism affects an estimated 11 million Americans, particularly women and the elderly.

In the U.S., the most common type of hypothyroidism is Hashimoto's disease, a condition caused when the immune system produces killer lymphocytes that destroy the thyroid. As the damaged thyroid gland produces less thyroid hormones, the pituitary gland secretes more thyroid-stimulating hormone (TSH) to encourage the thyroid to work harder. This increased demand on the thyroid may cause it to enlarge, resulting in what is commonly known as a goiter. Antibodies are produced that serve as a diagnostic test for Autoimmune Disease.

Signs and Symptoms
In the case of mild thyroid failure, patients often do not show obvious symptoms and thus may not even be aware of their condition. Left untreated, however, mild thyroid failure can progress to where symptoms begin to surface. Some of the signs and symptoms of hypothyroidism include: fatigue, hoarse voice, mood swings, difficulty swallowing, forgetfulness, intolerance to cold, dry, coarse skin and hair.

Detection and Diagnosis
Hypothyroidism may be difficult to detect because its often vague signs and symptoms are easily confused with other conditions, such as the natural aging process, menopause or stress. Many patients remain undiagnosed and untreated for years due to their lack of awareness of hypothyroidism and its signs and symptoms.

Fortunately, even mild hypothyroidism can be detected by a sensitive TSH (thyroid stimulating hormone) test, which enables physicians to identify thyroid disorders much earlier than with previous tests. By detecting hypothyroidism in its early stages, physicians may administer treatment and prevent the onset of symptoms.

The goal for treating hypothyroidism is to restore normal blood levels of thyroid hormone by replacing missing hormone. The treatment of choice for hypothyroidism involves supplementing the body's naturally produced hormone with a synthetic hormone tablet, levothyroxine sodium, which is generally taken for life.

After levothyroxine sodium therapy has been prescribed, periodic TSH tests are needed to monitor thyroid hormone levels. Because patient dosage requirements may change over time according to age, body weight, cardiovascular status and other diseases or medications, it is essential to monitor patients' medication needs on a regular basis. Monitoring precise dosages effectively prevents recurrence of symptoms of hypothyroidism and prevents over-replacement, which can in turn lead to hyperthyroidism.

Hypothyroid patients should not switch to different brands of levothyroxine sodium without consulting a physician. Both the American Association of Clinical Endocrinologists (AACE) and the American Thyroid Association (ATA) have released clinical guidelines recommending that patients be retested and their dosages adjusted accordingly if they switch levothyroxine sodium products. AACE further advocates that physicians treat patients with the same brand of levothyroxine throughout their lifetime. There is no place for Armour Thyroid in therapy. Beware of pseudoscientific non-diseases such as Wilson's.

Hyperthyroidism, a less common thyroid disorder, occurs when the thyroid gland becomes overactive and produces too much thyroid hormone. It affects approximately one to two million Americans, and is more prevalent among women, particularly those in their 30s and 40s. The most common form of this disorder is Graves' disease, the illness that affected Olympic athlete Gail Devers and former First Lady Barbara Bush. The cause of Graves' disease is unknown. Signs and Symptoms

The spectrum of possible signs and symptoms resulting from an overactive thyroid includes: irritability/nervousness, sleep disturbances, muscle weakness/tremors, enlarged thyroid (goiter), irregular menstrual periods, heat intolerance, weight loss, vision problems or eye irritation.

Treatment of an overactive thyroid may be complex and requires a long-term care plan. Once diagnosis is confirmed, treatment involves reducing the amount of thyroid hormone produced by the gland. Treatment methods for hyperthyroidism include antithyroid drug therapy, which blocks thyroid hormone production; radioactive iodine treatment, in which the overactive thyroid is disabled and reduced in size; and thyroid surgery to remove part or all of the gland, which is usually used to treat very young patients with Graves' disease and older patients with diseased thyroid glands. Radioactive iodine therapy is currently the treatment of choice in most cases in the United States. Patients are given a dose of radioactive iodine that essentially "shuts down" thyroid hormone production. Normal hormone levels must often be restored through levothyroxine sodium tablets. These patients require careful lifetime management to ensure they are receiving the proper dosage of thyroid medication.

Surgery is a good option for some, especially if a nodule is present that is suspicious of FNA.

All Thyroid.org

A good source for general information.