Thyroid Function Test and Regulation of Thyroid Hormone

    What is Thyroid?

    Thyroid is a butterfly-shaped gland in front of the neck present in our body. Through the hormones it produces, thyroid gland mainly regulates all metabolic processes in our body. There are different types of thyroid disorders which actually affect the size of the gland and its function. The thyroid uses iodine to produce vital hormones. Thyroxine, T4, is the primary hormone and in women’s body, after delivery via the bloodstream to the body’s tissues, a small portion of the T4 released from the gland is converted to triiodothyronine (T3), which is the most active hormone. When Thyroid hormones levels are low, the hypothalamus in the brain produces a hormone known as thyrotropin releasing hormone (TRH) that helps the pituitary gland to release thyroid stimulating hormone (TSH). TSH stimulates the thyroid gland to release more T4. If the pituitary gland and hypothalamus gets some disorders then also the thyroid gland can have problems.

    Thyroid Disorders Types

    • Hypothyroidism
    • Hyperthyroidism
    • Goiter
    • Thyroid nodules
    • Thyroid cancer

    Regulation of Thyroid Hormone Production

    Pituitary gland regulates that how much hormone should be present in blood, as per that it produces hormones and thus it prevents the overproduction or underproduction of thyroid hormones. If thyroid hormones get increased in the blood, then automatically production of TRH and TSH are decreased. So it is necessary that the level of thyroid hormone should be normal in the blood. If this regulatory system gets affected then it may result hyperthyroidism and hypothyroidism.

    Hypothyroidism happens when thyroid gland produces insufficient thyroid hormone. Some symptoms are:

    • Fatigue
    • Poor concentration
    • Dry skin
    • Constipation
    • Feeling cold
    • Fluid retention
    • Muscle and joint aches
    • Depression
    • Prolonged or excessive menstrual bleeding in women
    • Hashimoto’s thyroiditis

    Hyperthyroidism is a condition where excessive production of thyroid hormone happens. Some symptoms are:

    • Tremor
    • Nervousness
    • Fast heart rate
    • Fatigue
    • Intolerance for heat
    • Increase in bowel movements
    • Increased sweating
    • Concentration problems
    • Unintentional weight loss
    • Grave’s disease
    • Toxic multinodular goiter

    Thyroid Function Test

    How do thyroid disorders get diagnosed? Mainly blood tests are done to measure the levels of thyroid hormones and TSH. If patients come with any of the symptoms mentioned above, then doctors suggest to do blood tests from which it is identified the antibodies against thyroid tissue such as anti-thyroglobulin, anti-thyroperoxidase, or TSH receptor stimulating antibodies

    Imaging tests are commonly used when thyroid nodules or enlargement are present. Ultrasound can visualize the consistency of the tissue within the gland and can often reveal cysts or calcifications. Ultrasound examination cannot distinguish a benign from a malignant process.

    Thyroid scans using radioactive iodine are often performed to evaluate the function of thyroid nodules. Sometimes in case of detecting thyroid cancer, fine needle aspiration (FNA) and biopsy are done.

    Thyroid Function Test: Understand the Results

    Normal ranges

    • T3: 100-200 monograms of hormone per decilitre of blood.
    • T4: 4.6-12 ug/dl
    • TSH: Between 0.4 and 4.0 milli-international units of hormone per liter of blood (mIU/L).

    The level of T3 gets high then Grave’s disease may occur which is an autoimmune disorder associated with hyperthyroidism.

    If blood test results show the TSH reading above 2.0 mIU/L, you’re at risk for progressing to hypothyroidism.

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