LabCorp Test

Thyroid-stimulating Hormone (TSH) Blood Test

Quick Overview

Checks thyroid gland function.

Test #004259


Availability: In stock

Also Known As Third Generation TSH; Thyrotropin; hTSH
Preparation No fasting required. Stop biotin consumption at least 72 hours prior to the collection.
Test Results 1-2 days. May take longer based on weather, holiday or lab delays.

The TSH blood test is also known as a Third-Generation TSH or Thyrotropin. Fasting is not required before taking the test and results are available within one to two days.

TSH is a thyroid function test used to assist in the diagnosis of thyroid disorders, monitor thyroid replacement therapy in patients with hypothyroidism, diagnose and/or monitor female infertility problems, and occasionally the test is used to help evaluate pituitary gland function. While the test is most often used to help diagnose thyroid disorders in adults, expert opinions vary on the benefits of screening, and at what age to begin testing.

The test investigates for low thyroxine (T4); the differential diagnosis of primary hypothyroidism from normal, and the differential diagnosis of primary hypothyroidism from pituitary/hypothalamic hypothyroidism. High TSH levels are found primarily in hypothyroidism, while low TSH occurs in hyperthyroidism. When evaluating the effectiveness of therapy for hypothyroid patients receiving thyroid hormone preparation, low TSH values are typically found in states of excessive thyroid replacement. Normal results on a sensitive TSH blood test is therefore considered acceptable evidence of adequate thyroid replacement.

Additionally, a TSH assay can be considered when testing for thyroid disease. Results within the accepted reference interval provide strong evidence for euthyroidism, or a normally functioning thyroid.

Thyroid Disorder Symptoms

One type of thyroid disorder is Hypothyroidism which means that the thyroid gland in underactive. Some symptoms that can be related to this disorder are weight gain, dry skin, constipation, a feeling of being too cold, tiredness, or frequent menstrual periods. Another type of thyroid disorder is Hyperthyroidism which means that the thyroid gland is overactive. Symptoms associated with this disorder may include weight loss, rapid heart rate, nervousness, diarrhea, a feeling of being too hot, or irregular menstrual periods.

Where does TSH come from?

TSH is produced when the hypothalamus, a portion of the brain, releases a substance called thyrotropin-releasing hormone (TRH). TRH tells the pituitary gland to release TSH. TSH is a pituitary hormone that causes the thyroid gland to produce two hormones, Tri-iodothyronine (T3) and Thyroxine (T4). T3 and T4 help to control the body’s metabolism. 

What can Influence or make a TSH Level Fluctuate?

There are many different things that can influence high or low TSH level or fluctuation in the level. When TSH makes its way to the thyroid gland the level is dependent on the amount of T3 and T4 that is in the blood. Other factors that can have an effect on a TSH level are inflammation of the thyroid gland, genetics, pregnancy, thyroid cancer, medications, or too much or too little iodine in the diet.

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