No one single laboratory test is 100% accurate in diagnosing all types of thyroid disease. The enhanced sensitivity and specificity of tsh assays have greatly improved the assessment. An overview of the synthesis, regulation, and function of thyroid hormones, as well as the interpretation of thyroid function tests. O confirmation of normal thyroid function o evaluation of thyroid hormone suppression and replacement therapy o detection of subclinical thyroid disease o detection of cases of inappropriate secretion of tsh thyroid hormone resistance, tsh secreting pituitary tumours tsh 0. Reference values of laboratory tests of thyroid function. Tsh tests the best way to initially test thyroid function is to measure the tsh level in a blood sample. Usually the free or active portion of t4 and t3 is measured i. Thyroid function tests what is a thyroid function test.
Hussam elmouzi clinical pathologist al borg laboratory 2. However, there remain a few situations in which the results of tsh, free t4, and free t3 assays tend to point in different directions, as well as cases in whom thyroid. Topic in focus interpretation of thyroid function tests. Tsh testing should not be used in the presence of nti, pituitary disease or tshsuppressing drugs. Abnormal tft results guidance abnormal thyroid function tests. Pdf interpretation of puzzling thyroid function tests. Thyroid diseases are common and in most cases the interpretation of thyroid function tests is straightforward. Lots of basic information about the thyroid gland can be found in the separate leaflet called thyroid and parathyroid glands. These hormones are essential for normal growth, development and metabolic function. Pitfalls in the measurement and interpretation of thyroid function tests. The tsh test has been used for triage in the diagnosis of thyroid dysfunction, especially in cases of minimal thyroid failure subclinical hypothyroidism.
Is it possible to have a normal test result and still have thyroid disease. American thyroid association thyroid function tests what is the thyroid gland. A common pitfall in the interpretation of thyroid function tests is to overlook the confounding effects of nonthyroidal illness nti. Challenges in interpretation of thyroid function tests in. The thyroid gland is a butterflyshaped endocrine gland that is normally located in the lower front of the neck. They are mainly used to detect an underactive thyroid gland hypothyroidism and an overactive thyroid gland hyperthyroidism. Interpretation of laboratory thyroid function tests. Changes in tsh can serve as an early warning system often occurring before the actual level of thyroid hormones in the body becomes too high or too low. Diagnosing maternal thyroid dysfunction during all stages of pregnancy is very important for the outcome for both mother and foetus 1, 2. In many laboratories, a highly sensitive tsh assay second or third generation, with a limit of detection hyperthyroidism thyroid function tests only confirm the diagnosis. Screening for thyroid diseases especially those at high risk is cost effective as up to 20% of those with subclinical thyroid disease may turn to clinical thyroid disease timing and choosing the right thyroid test is the best approach in understanding the meaning of the results.
Disorders of thyroid function are common estimated uk prevalence is 14%. Thyroid hormones and thyroid function tests youtube. Aug 03, 2015 thyroid dysfunction can result in a wide range of symptoms and thyroid function tests tft are therefore one of the most common endocrine tests ordered in general practice. Interpretation of thyroid function tests semantic scholar. In most healthy individuals, a normal tsh value means that the thyroid is functioning properly. Due to its diverse clinical presentation physicians has to rely on thyroid function test. The interpretation of tft results however, can often be challenging. Thyroid tests decoding your thyroid tests and results wondering about your thyroid test results.
Thyroid testing interpretation cornell university college. Knowledge of this thyroid physiology is important in knowing what thyroid test or tests are needed to diagnose different diseases. Tsh testing is recommended every five years in subjects over 35 years old 1 d. Thus physicians must be aware of the conditions affect the normal value of thyro id hormone. Page 1 name of test optimal range 1 thyroid stimulating hormone tsh 0. Also, evaluation of thyroid function in hospitalized patients can be complicated by other illnesses and medications. Interpretation of the results of thyroid function tests is facilitated by an understanding of thyroid hormone physiology, especially the normal inverse relationship between free t 4 and tsh concentrations. Routine tsh testing in pregnant women is also recommended because undetected hy. A high tsh level indicates that the thyroid gland is not making enough thyroid hormone. Pitfalls in the measurement and interpretation of thyroid. The tsh test can detect tsh blood levels as low as 0.
Nti or sick euthyroid syndrome is a relatively common finding following any acute or chronic illness, and is defined by the absence of an intrinsic abnormality of hpt function rather it is. Thyroid function ordering algorithm nonhospitalized patients without known or suspected pituitary disease begin evaluation by ordering either the cascade approach thscm thyroid function cascade, serum all appropriate tests are performed automatically or order each test individually, beginning with. This guidance is to assist gps in decision making and is not intended to replace clinical judgment. Tests to evaluate thyroid function include the following. Thyroid dysfunction can result in a wide range of symptoms and thyroid function tests tft are therefore one of the most common endocrine tests ordered in general practice. Interpretation of thyroid tests common tests to examine.
Uk guidelines for the use of thyroid function tests. This may happen when one reference range is quoted for all age groups in the laboratory reports. Feb 26, 2020 thyroid function tests are blood tests which help to check the function of your thyroid gland. Is the basal temperature an alternative to thyroid function testing. Tsh should be used as the firstline thyroid function test to assess thyroid hormone status. In these cases, interpretation of thyroid function tests is best done by an endocrinologist. Pdf thyroid function test and its interpretation researchgate. Abnormal tft results guidance tsh high t4 normal t3 normal. Nonthyroidal illness rarely secondary hypothyroidism. When autoplay is enabled, a suggested video will automatically. The thyroid gland secretes thyroxine t4 and triiodothyronine. Uk guidelines for the use of thyroid function tests british thyroid.
The best way to initially test thyroid function is to measure the tsh level in a blood sample. Thyroid function tests american thyroid association. Women with hypothyroidism treated insufficiently with levothyroxine high serum concentration of thyrotropin tsh or serum free thyroxine t4 in the low normal range deliver babies with significantly lower iq andor other inhibited. Thyroid function tests are used to establish the level of thyroid function e.
Thyroid function is assessed by evaluating the serum concentrations of the free hormones thyroxine t 4 and triiodothyronine t 3 and by a number of indirect methods. Blood tests for thyroid functiontsh, total t4, free t3, tsi, and othersare an important part of diagnosing and treating thyroid disorders. Thyroid dysfunction can result in a wide range of symptoms and thyroid function tests tft are therefore one of. Although most thyroid function test patterns are easy to interpret, and usually concord with clinical assessment of thyroid status, a small subset of patients exhibit results. Interpretation of laboratory thyroid function tests authorstream. Interpretation of thyroid function tests current medical. Thyroid testing interpretation canine measurement of freet4 may be useful in differentiating dogs with true hypothyroidism from dogs with reduced thyroid function due to other chronic illness e. A blood sample is taken from a vein in the arm and sent off to the laboratory for analysis. Interpretation of puzzling thyroid function tests article pdf available in journal of the korean medical association 614. Thyroid function tests tfts is a collective term for blood tests used to check the function of the thyroid tfts may be requested if a patient is thought to suffer from hyperthyroidism overactive thyroid or hypothyroidism underactive thyroid, or to monitor the effectiveness of either thyroid suppression or hormone replacement therapy. Thyroid function tests are a series of blood tests used to measure how well your thyroid gland is working. Thyroid function test interpretation tft interpretation.
Thyroid function tests an overview sciencedirect topics. The usual blood tests done for thyroid function are tsh, t4 and sometimes t3. Laboratories use reference ranges to compare blood test results with results in the. T4 is the main form of thyroid hormone circulating in the. Interpretation of laboratory thyroid function tests the hidden health problem dr. Thyroid function tests the choice of firstline thyroid function tests depends on local arrangements and laboratory protocols. American association of clinical endocrinologists aace. However, important pitfalls and difficult cases still exist. A guide to thyroid function test interpretation tft interpretation, including the common tft patterns for hypothyroidism and hyperthyroidism. Thyroid disease frequently arises from autoimmune processes that stimulate overproduction of hormones hyperthyroidism or causes gland destruction that subsequently leads to underproduction of hormones hypothyroidism.
How to interpret thyroid function tests rcp journals. Effects of age on thyroid function test population reference ranges awareness that age has an effect on tshft4 levels is important in that failure to recognise this may lead to missed or undertreated thyroid disorders. While some conclusions can be drawn from a single test, a combination of test results are usually needed to establish the full nature of your thyroid health. Aug 10, 2015 interpretation of thyroid function tests dr.
As a result, interpretation of thyroid function tests is now generally straightforward, and more than 90% of people investigated are diagnosed with normal thyroid gland function. Learn about each test and what low, optimal, and high results may mean so you can work with your doctor to choose appropriate treatment. Testing for thyroid disease is indicated by either increased or decreased metabolism. Other tests physicians also use a variety of other tests to assess thyroid function. Thyroid dysfunction is one of the most common endocrine disorder leading to obesity. In ambulatory patients with intact hypothalamic and pituitary function, a normal tsh result excludes hypo or hyperthyroidism. The thyroids job is to make thyroid hormones, which are secreted into the blood and then carried to every tissue in the body. We propose that if assays for thyrotropin, free t3, and free t4 are all done, knowledge of these. Thyroid function tests tfts are a group of tests requested to help check how the thyroid gland is working, to diagnose thyroid gland disorders and to monitor the response of thyroid disorders to treatment.
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