Thyroid function tests are diagnostic procedures used to evaluate your thyroid gland's functioning. It can also be used to detect the cause of your thyroid disease.

Your thyroid is a small, butterfly-shaped gland in the neck just below the Adam's apple (voice box). It produces two thyroid hormones, the triiodothyronine (T₃) and thyroxine (T₄). These hormones travel through your blood and virtually have effect on every cells and tissues in your body.

Functions of Thyroid Hormones

Thyroid hormones affect your:

• metabolism
• Brain development
• Breathing
• Heart and nervous system functions
• Body temperature
• Muscle strength
• Skin dryness
• menstrual cycles in women
• Weight
• Cholesterol levels

Thyroid Hormone Production

Production of thyroid hormones is basically regulated by another hormone produced by the pituitary gland in the brain. The hormone is called the thyroid stimulating hormone (TSH). Once released, TSH travels to your thyroid where it stimulates production and release of T₃ and T₄ in your blood.

The need for thyroid function tests

Sometimes, your thyroid produces too little or too much of thyroid hormones causing abnormalities in your body functions.

Two of the most common thyroid problems are hyperthyroidism and hypothyroidism.

• Hyperthyroidism occurs when your thyroid becomes hyperactive and produces too much of its hormones leading to increased metabolic rate, high blood pressure, elevated heart rate, and weight loss, among others.
• Hypothyroidism results in too little thyroid hormones being produced causing decrease in your body function. It can lead to fatigue, weight gain, cold intolerance, and other related symptoms.

Because abnormalities in thyroid function have great effect on your body functions, it is important that tests and diagnostic procedures are done. Proper diagnosis is essential for proper treatment to commence.

Tests being done to assess thyroid function

Blood tests are used to detect the levels of thyroid hormones and TSH in the blood. Several blood tests used are the TSH test, T₄ and/or T₃ test, the Thyroid-stimulating Immunoglobulin (TSI) Test, and Antithyroid Antibody Test.

Radiologic tests, on the other hand, is either used to assess thyroid function or detect abnormalities in the thyroid gland. Common radiologic tests are the radioactive iodine uptake (RAIU) test and a thyroid scan.

More on Diagnostic Tests:

• Diagnostic Tests for Overactive Thyroid (Hyperthyroidism)
• Common Radiologic Tests for Thyroid Function

Related Topics:
Hypothyroidism
Hyperthyroidism
Thyroid Gland

Source:
Thyroid Function Tests. National Endocrine and Metabolic Diseases Information Service, NIDDK Website

Thyroid Diseases. National Library of Medicine (NLM) Website

Page Last Revised: January 18, 2011

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