Thyroid Hormones -- The Accelerators of the Body's Machine

The thyroid gland is one of the most important hormonal glands of our body. Lodged on the front sides of the neck, closely adherent to the Adam's apple (the thyroid cartilage), the thyroid gland is very important both during early and later life. The manufacture of its critical hormonal secretions that are directly discharged into the blood, requires the presence of sufficient amounts of iodine in the diet. (This is the reason why commercial suppliers add iodine compound to regular table salt.)

Diseases of the thyroid gland are manifested by changes in the composition or amount of the hormones, by the enlargement of the thyroid, or by both. Failure to produce sufficient thyroid hormones during childhood results in physical and mental retardation (cretinism). In adulthood, reduced secretions of thyroid hormones due to inadequate activity of the gland, results in slowing down of body functions (decreased metabolism) and functional impairment. Excessive secretions of the thyroid hormones, result in persistent speeding up of the body activities (accelerated metabolism) that may also result in organ damage. Finally, uncontrolled growth of the thyroid tissue or cancer may invade the adjacent tissues of the neck, spread to distant sites (metastasize), and if unchecked may result in death.

Enlargement of the thyroid (which normally weighs half an ounce or so) may be generalized or focal. The diffuse enlargement (or goiter) may be associated with increased, normal, or decreased hormone secretion. Truly focal enlargement usually is caused by growths that may be benign (and often secrete hormones) or cancerous (which are more likely than not, to be "cold" i.e., non secreting hormones).

Hyperthyroidism (excessive secretion of thyroid hormones) or Thyrotoxicosis:

Hyperthyroidism is a disease resulting from high circulating thyroid hormone levels. Most often it results from unknown causes (Graves's disease), but in some cases is a result of excessive hormonal activities of a benign tumor (adenoma), or an inflammation of the thyroid gland (thyroiditis).

Other causes of hyperthyroidism, such as a hyperactive cancerous growth, are rather rare. The symptoms are what we would expect from an accelerated metabolic rate (biochemical activity of the body). Patients experience nervousness, intolerance to heat, palpitations, rapid pulse, weakness, shortness of breath on exertion, sweating of hands, fine tremor of the hands, fulness in the throat, diarrhea and abnormal or a lack of menstruation. The eyes may bulge excessively and eye injury may occur. Older people often develop depression.

If hyperthyroid patients are exposed to increased stress, such as trauma or illness, they may develop a severe life threatening form of hyperthyroidism known as "thyroid storm," a dramatic increase in all the signs and symptoms of thyrotoxicosis. The thyroid crisis is characterized by extreme irritability, delirium or coma, high fever, accelerated pulse and severe drop in blood pressure. In the past it commonly appeared after surgery in patients who were poorly prepared for surgery. Today, it is more common in untreated or inadequately treated non-surgical patients. The diagnosis is confirmed by laboratory tests demonstrating the presence of high levels of thyroid hormones, or other types of hormones known to stimulate the activity of the thyroid gland (TSH). The treatment depends on the cause of the hyperthyroidism.

Graves disease is treated with chemicals (Propylthiouracil or Methimazole) that depress the activity of the gland. Clinical improvement is usually seen within a week or two, and normal activity usually returns within 2-3 months. The drugs are usually continued for 6 months to a year. Side effects of the drugs include rashes, depression of bone marrow with anemia, arthritis, and chemical hepatitis (inflammation of liver), but they do not cause permanent thyroid damage. Other medications also used include iodine (one drop of iodine salt in juice), propranolol (Inderal), and radioactive iodine. Benign tumors are treated by surgery and anti-thyroid drugs may be used in the interim. Inflammation of the thyroid (thyroiditis) may require no therapy or treatment with aspirin or anti-thyroid drugs.

Hypothyroidism (decreased activity of the thyroid gland) or Myxedema:

Hypothyroidism, a deficiency in normal thyroid levels is a result of either direct thyroid disease or a decrease in the hormones responsible for stimulating the thyroid gland (TSH or thyroid stimulating hormone).

Without thyroid enlargement, hypothyroidism may be of unknown origin (idiopathic) or may follow thyroid surgery, or administration of radioactive iodine.

With thyroid enlargement, hypothyroidism is associated with a specific type of thyroid inflammation known as Hashimoto's disease. Drugs and iodine deficiency in the diet are rare causes.

Signs and symptoms include fatigue, weakness, slow movement, cold intolerance, constipation, hair loss, increased menstrual flow, carpal tunnel syndrome, dry skin, swelling of face and extremities (myxedema), memory impairment, hearing loss, hoarseness and occasionally low heart rate and low body temperature (hypothermia.) Hypothyroid patients show increased sensitivity to narcotics and general anesthetic agents, and elective surgery should be avoided because dangerous respiratory depression commonly occurs.

Hypothyroidism is generally not a dangerous condition if properly controlled. However, uncontrolled or severe, chronic hypothyroidism may result in coma (myxedema coma) if the patient is exposed to cold, infections, respiratory depressants, allergic reactions or a metabolic stress.

Laboratory findings include-- in addition to low levels of thyroid hormones--low blood sugar, elevated blood cholesterol and neutral fats, and other biochemical abnormalities. Patients may also have slight anemia and decreased electrocardiographic tracings.

The treatment consists of administration of replacement thyroid hormone (Levoththyroxine or Synthroid).

Conclusion:

It is obvious then that the thyroid is a small but very powerful gland that plays a vital role in the regulation of many of our bodily functions. There are multiple derangements that can occur and they often have devastating effects if not treated in a timely manner.