Introduction:
Thyroid-stimulating hormone is produced by the anterior pituitary gland and is responsible for stimulating the thyroid gland to produce thyroid hormones. Thyroid-stimulating hormone test is a simple blood examination to measure the levels of thyroid-stimulating hormone in the blood. The test is used to evaluate the proper functioning of the thyroid gland. Thyroid-stimulating hormone test is indicated in patients with symptoms like; fatigue, unusual weight loss or weight gain, increased heart rate, infertility, difficulty in sleeping, etc.
What Is Thyroid-Stimulating Hormone?
Thyroid-stimulating hormone, also referred to as TSH, is a glycoprotein hormone produced and secreted by the anterior pituitary into the bloodstream. It serves as the thyroid gland's primary stimulant for producing thyroid hormones. Additionally, it influences the growth of thyroid follicular cells. The thyroid-stimulating hormone controls the production of thyroid hormones (thyroxine and triiodothyronine). Any imbalance in the levels of the thyroid-stimulating hormone can lead to increased or decreased production of thyroid hormones which can, in turn, lead to thyroid gland disorders like hyperthyroidism (over-active thyroid) or hypothyroidism (underactive thyroid), etc.
How Is Thyroid-Stimulating Hormone Regulated?
The release of the thyroid-stimulating hormone is regulated by the hypothalamic-pituitary axis. The hypothalamus produces thyrotropin-releasing hormone (TRH), which stimulates the pituitary gland to release thyroid-stimulating hormone (TSH). The thyroid-stimulating hormone, in turn, stimulates the thyroid gland to produce thyroid hormones by controlling several processes involved in their synthesis. If the levels of the thyroid hormones are too high, these hormones have a negative effect on the pituitary gland and prevent the thyroid-stimulating hormone from being produced. Additionally, they stop the hormone thyrotropin-releasing hormone from being produced.
What Is the Thyroid-Stimulating Hormone Test?
Thyroid-stimulating hormone test is a blood test that measures the amount of thyroid-stimulating hormone present in the blood. Since the thyroid-stimulating hormone is crucial for the production of thyroid hormones by the thyroid gland, its level should be within the normal range to prevent the development of any thyroid gland disorders due to subsequent imbalances of thyroid hormones. Moreover, elevated or decreased levels of the thyroid-stimulating hormone can be an indication of thyroid gland dysfunction.
Why Is a Thyroid-Stimulating Hormone Test Done?
Thyroid-stimulating hormone test is done to determine whether the thyroid gland is functioning correctly. It can also identify thyroid conditions in the absence of symptoms. A thyroid-stimulating hormone test is also done to determine the underlying reason for abnormal thyroid hormone levels.
Common thyroid conditions diagnosed with the help of thyroid-stimulating hormone tests are:
Hypothyroidism: A condition characterized by decreased production of the thyroid hormone. Common causes of hypothyroidism include:
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Hashimoto’s Thyroiditis: The body attacks its thyroid cells due to this autoimmune disorder. The thyroid is consequently unable to produce an adequate amount of thyroid hormones.
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Thyroiditis: It is a condition characterized by inflammation of the thyroid gland. It frequently results from a viral infection or an autoimmune disorder.
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Post-partum Thyroiditis: Post-partum thyroiditis develops after childbirth and is a temporary condition that may subside after some time.
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Iodine Deficiency: Iodine is used by the thyroid gland to produce thyroid hormones. A lack of iodine can cause hypothyroidism. The condition is common in developing countries and in people with low socioeconomic status.
Hyperthyroidism: It is a thyroid gland disorder characterized by increased thyroid hormone levels. Common causes of hyperthyroidism include:
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Graves’ Disease: The thyroid enlarges and produces excessive hormones due to this condition.
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Thyroiditis: It is a condition characterized by inflammation of the thyroid gland. It frequently results from a viral infection or an autoimmune condition. It usually leads to hypothyroidism, but it may lead to hyperthyroidism for a short period.
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Excess Iodine: The thyroid may overproduce thyroid hormones if there is excessive iodine in the body. Continued usage of iodine-containing medication usually leads to excess iodine in the body.
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Thyroid Nodule: These non-cancerous tumors can occasionally develop on the thyroid. The thyroid may start producing too many hormones when these nodules begin to enlarge.
How Is a Thyroid-Stimulating Hormone Test Done?
It is crucial to prepare for the TSH test. There is no additional preparation for the TSH test. It is essential to inform the doctor if an individual is taking medication that could affect the accuracy of the TSH test.
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Amiodarone.
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Dopamine.
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Lithium.
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Potassium Iodide.
The doctor or healthcare professional may advise stopping these medications for a few days before undergoing a thyroid-stimulating hormone test. A thyroid-stimulating hormone test is done in the following steps:
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Cleaning and sterilizing the area of sampling with an antiseptic solution.
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A tourniquet (a band, rubber, or cloth) is wrapped around the arm to stop blood circulation and make the vein swell with blood, making collecting blood samples easier.
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After locating the vein, a needle is inserted into the vein, and a blood sample is collected.
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After collecting the sample, the puncture site is covered with a bandage to stop bleeding and prevent infection.
What Do the Results of Thyroid-Stimulating Hormone Test Mean?
A correct interpretation of the results is the most important part of any diagnostic procedure.
During a thyroid-stimulating hormone test, high levels of the hormone will indicate:
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The average level of thyroid-stimulating hormone is between 0.4 to 4.0 mill units per liter. If the TSH level is above 4 or 5, it is an underactive thyroid.When the thyroid gland does not produce an adequate amount of thyroid hormones, the pituitary glands produce more TSH to stimulate the thyroid gland to produce more thyroid hormones.
During a thyroid-stimulating hormone test, low levels of the hormone will indicate:
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Presence of various diseases like Graves’ disease, excess iodine in the body, and thyroid hormone replacement therapy.
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Lower-than-average readings may occur due to drugs like Steroids, Dopamine, or Opioid painkillers. Additionally, taking Biotin (a B vitamin supplement) may decrease TSH levels.
What Is the further Treatment based on the Results of a Thyroid-Stimulating Hormone Test?
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An elevated level of TSH suggests an underactive thyroid gland which means a low level of thyroid hormones in the body. This condition is easily treated by thyroid hormone replacement therapy.
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Decreased levels of TSH suggest an overactive thyroid gland, which means a high level of thyroid hormone in the body. This condition is treated by radioactive iodine therapy to slow down the thyroid gland, anti-thyroid medication, surgery to remove the thyroid, etc.
Conclusion:
Thyroid-stimulating hormone test is a simple yet useful test to measure the levels of thyroid-stimulating hormone in the blood. The average TSH level should be between 0.4 to 4.0 mU/L. However, the levels may also change in certain physiologic conditions like pregnancy. Any imbalance in the level of TSH is suggestive of the presence of some kind of thyroid disorder. Moreover, increased or decreased levels of TSH can be easily treated by thyroid hormone replacement therapy or by removing the underlying cause of the condition.
