Hypothyroidism / Hashimato's Disease Panel

Thyroid Stimulating Hormone (TSH) test measures the amount of TSH in your blood which helps to find out if the thyroid gland is working normally or not. Low TSH levels indicate hyperthyroidism and high TSH levels indicate hypothyroidism.

In case of hyperthyroidism, the thyroid gland produces very high amounts of thyroid hormones (T3 and T4) and you may experience symptoms of weight loss, rapid heartbeat, tremors, sweating, anxiety, increased sensitivity towards heat, etc. In case of Hypothyroidism, there is a decrease in the production of thyroid hormones (T3 and T4) which may cause weight gain, fatigue, slow heart rate, increased sensitivity towards cold, depression, dry and thin hair, etc.

There is a feedback system in the body to maintain stable amounts of the thyroid hormones (T3 and T4) in the blood. TSH signals the thyroid gland to make and release the thyroid hormones (T3 & T4) into the blood when the level of thyroid hormones is low and can also signal the thyroid gland to lower the production of thyroid hormones when the level of thyroid hormones is very high. So, when the thyroid hormone (T3 and T4) levels decrease, the pituitary gland is stimulated to release TSH and this high TSH level, in turn, stimulates thyroid gland to release more thyroid hormone (T3 & T4) from the thyroid gland and the vice-versa happens when the thyroid hormone levels are very high.

TPO is also known as thyroid peroxidase or iodide peroxidase which is an enzyme mainly expressed in the thyroid gland. The thyroid gland is positioned at the lower part of the neck. TPO is found in the cells of the thyroid follicle where it helps in the production of the thyroid hormones. Its basic function is to oxidize iodide ions to form iodine atoms which assist in the production of thyroxine (T4) or triiodothyronine (T3), the thyroid hormones. TPO is an antigenic determinant of autoantibodies in diseases like autoimmune disorders of the thyroid. These antibodies are called as anti-TPO antibodies (anti-Thyroid peroxidase antibodies) which activates complement and might be associated with dysfunction of thyroid and its pathogenesis. To assess these antibodies, Anti-TPO antibody test is carried out.

The thyroid gland secretes the following hormones:

• Triiodothyronine (T3)

• Thyroxine (T4)

Thyroid Stimulating Hormone (TSH) is a hormone secreted into the blood by the pituitary gland (a gland present in the brain) which tells your thyroid gland to make and release the thyroid hormones (T3 & T4) into your blood. The thyroid gland uses the iodine gained from food to make the thyroid hormones.

The thyroid hormones are essential for growth and metabolism. If the thyroid gland produces very high amounts of T3 and T4 hormones, you may experience symptoms like weight loss, rapid heartbeat, tremors, sweating, anxiety, increased sensitivity to heat, etc. This is known as hyperthyroidism.

The decreased production of thyroid hormones (T3 and T4) results in hypothyroidism which may cause weight gain, fatigue, slow heart rate, increased sensitivity to cold, depression, dry and thin hair, etc.

There is a feedback system in the body to maintain stable amounts of the thyroid hormones (T3 and T4) in the blood. When the levels of thyroid hormones decrease, the pituitary gland is stimulated to release TSH. High TSH, in turn, increases the release of thyroid hormones (T3 & T4) from the thyroid gland and vice-versa.

T4 hormone constitutes about 90% of thyroid hormones and circulates in the blood in two forms:

1) Bound form - It is bound to the proteins present in the blood and this prevents it from entering the body tissues. The three main proteins in the blood that the T4 hormone is bound to are albumin, transthyretin and Thyroxine-binding globulin (TBG), also called Thyroid hormone binding globulin (THBG).

2) Free form - This is the active form which enters the body tissues where it's needed. Free Thyroxine (FT4) constitutes only 0.3% of the total T3 hormone.

Hence, the T4 hormone can be measured as Free T4 or Total T4. Total T4 includes both the bound and the free forms, circulating in the blood and can be affected by the amount of protein available in the blood to bind to them. Therefore, Thyroxine (T4) Free Test is a useful indicator of the T4 levels in the blood when binding proteins are increased or decreased.

Thyroxine (T4) Free Test is also done as a part of the Thyroid Profile Free Test which includes two more tests: Thyroid Stimulating Hormone (TSH) and Triiodothyronine (T3) Total.