The thyroid gland is subdivided by capsular septa into lobules containing follicles. Guidelines for thyroid function testing in primary care. Thyroid function tests are used to check whether your thyroid is working normally. In the patients with obvious features of hypothyroidism or hyperthyroidism thyroid function tests only confirm the diagnosis. We propose that if assays for thyrotropin, free t3, and free t4 are all done, knowledge of these patterns coupled with clinical details and simple additional tests allow a diagnosis to be made in almost all cases. Classification of tests based on functions of thyroid tests measuring blood levels of thyroid hormones. Uk guidelines for the use of thyroid function tests. One way to evaluate the performance of the thyroid is through blood testing. Interpretation is a topic covered in the harriet lane handbook to view the entire topic, please sign in or purchase a subscription the harriet lane handbook app and website provides pediatric diagnosis and treatment, pediatric management algorithms, and pediatric drug formulary from experts at johns hopkins university. To help an individual interpret their thyroid lab tests and to recommend what thyroid labs they should have tested in the future. Tsh stimulates the thyroid gland to produce and release the thyroid hormones thyroxine t4 and triiodothyronine t3. Jul 02, 2011 interpretation of laboratory thyroid function tests 1. In most cases, interpretation of thyroid function tests with free hormone assays and tsh is straightforward. Hussam elmouzi clinical pathologist al borg laboratory.
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. American thyroid association thyroid function tests what is the thyroid gland. Tsh is a very sensitive marker of primary thyroid disease. Tsh is the key hormone for diag nosing hyperthyroidism and hypothyroidism. Treatment for subclinical hypothyroidism is recommended when. Interpretation of laboratory thyroid function tests the hidden health problem dr. Thyroid function tests drnehamahajan md pathology 2. The test is believed to be the most comprehensive panel clinically available to identify mutations associated with four gene markers indicated by the american thyroid association for the clinical management of indeterminate thyroid biopsies. Interpretation of thyroid function tests tfts is generally straight forward. T4 is the main form of thyroid hormone circulating in. Tsh is most common screening test ultrasound of thyroid thyroid scan. Jul 01, 2012 thyroid diseases are common and in most cases the interpretation of thyroid function tests is straightforward.
Thyroid function tests american thyroid association. Knowledge of this thyroid physiology is important in knowing what thyroid test or tests are needed to diagnose different diseases. Interpretation of laboratory thyroid function tests. 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 thyroidsuppression or hormone replacement therapy. The following test panels are used to evaluate the overall health of your thyroid by determining related hormone levels. Amiodarone interferes both with the synthesis of tsh, with iodine uptake by the thyroid gland and with conversion of t4 to t3. Laboratory evaluation of thyroid function shashank r joshi department of endocrinology, grant medical college and sir jj group of hospitals, endocrinologist, lilavati and bhatia hospital, mumbai. The assessment of thyroid function in newborns, especially premature infants, is challenging as are the interpretation of thyroid function tests in infancy through childhood.
Interpretation of laboratory thyroid function tests authorstream. Hence before interpreting a result as abnormal, compare it with ageappropriate normal range. Understanding thyroid function tests and normal ranges. The results of thyroid function tests tfts must always be interpreted in light of the clinical status of the. Brent wisse, md, board certified in metabolismendocrinology, seattle, wa. Tsh is above the upper reference interval limit, but. These may also be signs of poor adrenal function, so talk with your healthcare professional to decide whether a thyroid or an adrenal function test is best for you. The patented thyroflex is a noninvasive state of the art system to test, diagnose, titrate, and manage thyroid conditions. These septa also serve as conduits for blood vessels. Serum total t4 and total t3 steadily increase during pregnancy to approximately 1. A high tsh level indicates that the thyroid gland is not making enough thyroid hormone.
Aug 03, 2015 pdf version interpretation of thyroid function tests dr. Thyroid hormones help the body use energy, stay warm and keep the brain, heart, muscles, and other. The introduction of sensitive thyrotropin assays and free thyroid hormone measurements has simplified the interpretation of thyroid function tests. It may be impossible to interpret tfts in isolation and decisions may need to be taken on clinical grounds or on the pattern of change in tfts over a period of time. Interpretation of thyroid tests common tests to examine. About 5% to 15% of thyroid nodules detected in the united states. Tbg in pregnancy vfree t34 vtbg in cirrhosis and steroid. Pth is typically ordered to investigate hyperor hypocalcemia, but it.
However, unusual conditions can generate common patterns of thyroid function, easily confused with more straightforward diseases panel 2, panel 5, panel 6, and unusual patterns of test results panel 3, panel 4, panel 7. The thyroid function test is a group of common tests used to evaluate how the thyroid is functioning. The thyroid s job is to make thyroid hormones, which are secreted into the blood and then carried to every tissue in the body. Blood tests for thyroid function tsh, total t4, free t3, tsi, and othersare an important part of diagnosing and treating thyroid disorders. Interpretation of thyroid function tests current medical. Illness has a significant impact on thyroid function tests and assessment in this group is described by drs. It is surrounded by a dense irregular collagenous connective tissue capsule, in which posteriorly the parathyroid glands are embedded. An imaging test typically shows uptake of radioactive iodine by normal thyroid tissue. The sensitive thyrotropin tsh assay reflects thyroid hormone feedback to the pituitary, and is diagnostic of both thyroid h mone excess as well as deficiency. Abnormal tft results guidance abnormal thyroid function. Because thyroid hormone is needed to get the bodys furnace working, low thyroid function often results in low body temperature. The thyroid is the only location in the body that takes up iodine, so when radioactively labeled iodine is given, it is taken up by the thyroid gland.
The best way to initially test thyroid function is to measure the tsh level in a blood sample. The clinical status of the patient is the most important factor that needs to be. Thyroid function tests are blood tests used to evaluate how effectively the thyroid gland is working. In most healthy individuals, a normal tsh value means that the thyroid is functioning properly. Nitin kapoor, mbbs, md,dm endo, abbm usa, post doc. Anatomy, physiology and pathology of the thyroid gland. This article aims to address these issues by discussing the variables preanalytical and analytical see table i that affect the interpretation of test results, in the hope that clinicians will have a better understanding of how to interpret discrepant test results in the clinical context. Clinical examination a comprehensive collection of clinical examination osce guides that include stepbystep images of key steps, video demonstrations and pdf mark schemes.
The most common thyroid function blood test measures the levels of thyroidstimulating hormone tsh, triiodothyronine t3 and thyroxine t4. To perform a thyroid function test, a blood sample is drawn from a vein in your arm and collected in a tube. The most common thyroid function blood test measures the levels of thyroid stimulating hormone tsh, triiodothyronine t3 and thyroxine t4. Patients newly diagnosed with hypothyroidism whilst pregnant, s hould have t4 treatment commenced immediately with a starting dose of 100 microgram daily. 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. This blood test is the most sensitive test of thyroid function available. Interpretation thyroidstimulating hormone tsh this test is used to identify primary hypothyroidism and to differentiate it from secondary pituitary and tertiary hypothalamus hypothyroidism. Learn about each test and what low, optimal, and high results may mean so you can work with your doctor to choose appropriate treatment. Total t4 the free hormone and the hormone bound to carrier proteins free t4 the main thyroid hormone in your blood a precursor for t3 tsh the hormone from the pituitary gland that stimulates the thyroid to.
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. Interpretation of thyroid function tests sciencedirect. A proportion of cases have normal t4 with suppressed tsh. If results of the tsh test are abnormal, one or more additional tests are needed to help determine the cause of the problem.
If a problem with binding proteins is suspected, docs sooner order a thyroid binding globulin tbg test. Topic in focus interpretation of thyroid function tests cmi. No one single laboratory test is 100% accurate in diagnosing all types of thyroid disease. Pdf thyroid function test and its interpretation researchgate. The number of people having thyroid function testing in australia has. Thyroid tests decoding your thyroid tests and results wondering about your thyroid test results. Thyroid dysfunction can result in a wide range of symptoms and thyroid function tests tft are therefore one of. Bmi36 kgm2 has sedentary lifestyle and very limited physical activity.
A raised t4 and t3 with suppressed tsh and an elevated tsh receptor antibody level confirms the diagnosis of graves disease. Tsh testing should not be used in the presence of nti, pituitary disease or tshsuppressing drugs. Reference values of thyroid function test test range tsh 0. Interpretation depends on whether the patient is taking thyroxine. Page 1 name of test optimal range 1 thyroid stimulating hormone tsh 0. American proficiency institute 2005 3rd test event educational commentary thyroid and parathyroid testing cont.
A further assessment of thyroid function tests should be performed after 2 weeks to ensure ft4 is ideally 16 21 pmoll. Pitfalls in the measurement and interpretation of thyroid. Tsh should be used as the firstline thyroid function test to assess thyroid hormone status. Thyroid function test, any laboratory procedure that assesses the production of the two active thyroid hormones, thyroxine t 4 and triiodothyronine t 3, by the thyroid gland and the production of thyrotropin thyroidstimulating hormone, tsh, the hormone that regulates thyroid secretion, by the pituitary gland. 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. An external file that holds a picture, illustration, etc. They are the most frequently measured endocrine tests. To educate on what each lab test represents, what are the variables involved with the each lab test, and what may influence any given lab test. Osceaid uk osceaid tips thyroid binding globulin tbg. The thyroids job is to make thyroid hormones, which are secreted into the blood and then carried to every tissue in the body. Thyroglobulin is synthesized by these thyroid cells and secreted across the apical membrane into the follicular lumen fig. Interpretation of laboratory thyroid function tests 1.
Bulletin board archived bulletin board about john latest ideas symptoms tests and drugs weight loss experiment hyperthyroidism hypothyroidism supplement list medical science heredity other diseases thyroid physiology deeper studies nutrients and toxics hair analysis book reports glossary table of contents. Guidelines for the use of thyroid function tests greys. This is the most common setting for thyroid function test measurement and a rational. Thyroid diseases are among the most prevalent of medical conditions. Thyroid hormone influences a wide range of processes, including growth, development, maturation of the nervous system, reproduction, metabolism, and muscle function. It uses reflexes, resting metabolic rate and symptoms to accurately determine thyroid function. Thyroid function tests are utilized by essentially all medical practitioners, across every clinical setting, in patients from newborns to the elderly. The thyroid gland is a butterflyshaped endocrine gland that is normally located in the lower front of the neck. Conclusion tsh is a good screening test to assess thyroid function in an outpatient setting. Thyroid diseases are common and in most cases the interpretation of thyroid function tests is straightforward. Topic in focus interpretation of thyroid function tests. Indications for thyroid function testing screening for thyroid dysfunction which thyroid function test.
These tests include the thyroid stimulating hormone test tsh, free and total thyroxine tests ft 4,t 4, the free and total triiodothyronine tests ft 3,t 3, the thyroxinebinding globulin test tbg, and the tuptake test. Interpretation of thyroid function tests during pregnancy. 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. Even though obsolete, i plan to continue getting a total t4 and maybe the free thyroxine index because i have results on those 2 tests going back to 1992 and 1988. Tsh is most common screening test ultrasound of thyroid thyroid scan thyroid fine needle biopsy gets a small tissue to look under microscope. Pdf version interpretation of thyroid function tests dr. As a baseline screening test tsh sampling will be done on all samples received for tfts.
Free t4 will be measured and a report issued containing both results and if. The thyroid gland is normally regulated by thyroidstimulating hormone tsh, also called thyrotropin, which is secreted by the pituitary. A common pitfall in the interpretation of thyroid function tests is to overlook the confounding effects of nonthyroidal illness nti. Feb 22, 2018 the thyroid function test is a group of common tests used to evaluate how the thyroid is functioning. It is also requested routinely in conditions linked. Thyroxinet4 this test is used to evaluate thyroid function.
These tests include the thyroidstimulating hormone test tsh, the thyroxine test t4, the triiodothyronine test t3, the thyroxinebinding globulin test tbg, the triiodothyronine resin uptake test t3ru, and the longacting thyroid stimulator test. Free t4 and t3 will be done if requested for and if warranted by the supplied brief history and on samples with abnormal tsh results. Thyroid function test interpretation tft interpretation. The best and most widely used tests are measurements of. By comparing the values of thyroid tests, a doctor can determine whether a person has. The thyroidal secretion consists of thyroxine t 4 and triiodothyronine t 3. Interference with tft interpretation due to committant drug therapy. Thyroid scans using radioactive iodine are often performed to evaluate the function of thyroid nodules. These lab tests can be used to diagnose common thyroid disorders like hashimotos thyroiditis, hyperthyroidism, and hypothyroidism. Normal changes in thyroid function tests during pregnancy include a transient suppression of thyroid stimulating hormone and stimulation of triiodothyronine.
We propose that if assays for thyrotropin, free t3. Interpretation thyroid stimulating hormone tsh this test is used to identify primary hypothyroidism and to differentiate it from secondary pituitary and tertiary hypothalamus hypothyroidism. However, important pitfalls and difficult cases still exist. Tsh is the most useful parameter in screening for thyroid dysfunction in most non critically ill patients since tsh is almost always suppressed in hyperthyroidism. The functional unit of the thyroid gland, for hormone synthesis and storage, is the thyroid follicle. Many clinical chemistry laboratories offer thyroid stimulating hormone tsh alone as a firstline test of thyroid function, and only reflex a free thyroxine ft4 test if the tsh. Aug 10, 2015 topic in focus interpretation of thyroid function tests cmi. 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. A guide to thyroid function test interpretation tft interpretation, including the common tft patterns for hypothyroidism and hyperthyroidism. Many clinical chemistry laboratories offer thyroidstimulating hormone tsh alone as a firstline test of thyroid function, and only reflex a free thyroxine ft4 test if the tsh. This blood test measures thyroid health to detect potential imbalances in thyroid hormone levels. Hussam elmouzi clinical pathologist al borg laboratory 2. Thyroid function tests leeds teaching hospitals nhs trust. Appropriate interpretation of tsh, t3, t4 values is extremely important in arriving at the correct diagnosis when newborns are screened for congenital hypothyroidism, with due.
1418 1303 272 1441 1362 86 134 1411 292 1231 4 1246 1429 560 1131 1215 835 391 431 711 113 965 73 1420 114 1012 895 57 1522 451 14 918 739 1210 959 1015 222 416 1193 1478 850