Educationals

The thyroid gland is a small gland at the base of the neck. It has 2 lobes like the wings of a butterfly connected by a bridge called isthmus; each lobe lies on either side of the windpipe or trachea.

The thyroid gland makes, stores and secretes thyroid hormones (a general term used for secretions of thyroid gland that are released directly into the blood stream in extremely minute quantities). These thyroid hormones are called T3 (Triiodothyronine) and T4 (Thyroxine). Iodine plays an important role in the functioning of the thyroid gland. It is the chief component of the thyroid hormones and is essential for their production. Iodine is obtained from water and food.

Regulation of Thyroid Hormones Synthesis The production of thyroid hormones by the thyroid gland is controlled by another gland, the pituitary (situated in the brain), as well as a part of the brain called hypothalamus. The pituitary exercises control over the thyroid through the release of thyroid stimulating hormone (TSH). The concentration of thyroid hormones in the blood is finely regulated. The thyroid gland, pituitary gland and the hypothalamus work together to control the thyroid function. Like a thermometer in a thermostat which senses the temperature in a room, the pituitary constantly senses the amount of thyroid hormones in the blood. When there is an increase or decrease in the levels of thyroid hormones, TSH is suppressed or elevated respectively. Thus, balance is maintained in a normal person.

Thyroid hormones control many important functions in our body. The thyroid hormones influence every cell in our body and help control the body's various functions e.g. physical and mental development, metabolism, reproduction etc. They act like tuning of the engine in an automobile.

When the thyroid gland is enlarged it is called goitre. Normal thyroid gland can be felt but not seen. When the gland is enlarged, it is visible. The goitre may have normal, increased or decreased thyroid hormone levels.
The disorders of thyroid can manifest as hyperthyroidism or hypothyroidism.

If the gland produces more than the normal level of thyroid hormones, the condition is known as hyperthyroidism. This is also accompanied by low levels of TSH in the blood. Decreased level of thyroid hormones causes your body to enhance its metabolism resulting in nervousness, fast heart beats and weight loss among other symptoms.

Hypothyroidism is the result of an underactive thyroid gland which does not produce enough thyroid hormones to keep the body working normally. Consequently, in hypothyroidism the levels of thyroid hormones are decreased and TSH elevated.

In adults, the commonest cause of hypothyroidism is thyroid shrinkage and failure due to production of antibodies against the thyroid. This tendency of the body to produce antibodies against its own tissue may run in families. Hypothyroidism can also occur after treatment for hyperthyroidism. The other causes are iodine deficiency, thyroid surgery and treatment with certain drugs.
In hypothyroidism, there is slowing down of almost all functions of the body. It can occur in any age and is seen in both sexes, though reported to be more common in women than in men. Sometimes, in a very mild form of hypothyroidism, there may not be any clinical signs or symptoms. It is the early phase of the disease and may be diagnosed when routine thyroid hormone/TSH estimation is undertaken as is done in those with family history of thyroid disease.