The practical application of thyroid function tests.
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Humans↗
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[New methods of thyroid function tests].
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Humans↗
Combined phenytoin and salicylate effects on thyroid function tests.
To evaluate the effects of salicylates (ASA) on thyroid function tests (TFT's) in patients already taking phenytoin (DPH), 6 adults received a daily dose of DPH to achieve a steady state serum DPH. ASA was then added stepwise (325, 650, 975 mg q 4hr) at 2-day intervals. TFTs, total serum and free salivary DPH were measured. Therapeutic steady state phenytoin levels caused a significant decrease in serum free thyroxine (FT4), total T4, total T3 (TT3) and a significant but slight increase in T3RU. The TSH remained normal. When ASA was co-administered with DPH, the serum free DPH increased, the total T4, TT3, FT4 significantly decreased further, and the T3RU significantly declined toward pre-treatment levels. The decrease of FT4 was in contrast to the increase in FT4 known to occur with ASA alone. Despite the decline in total T4, TT3, and FT4, the TSH remained normal. In conclusion, when ASA is co-administered with DPH, further alterations in TFTs occur which require cautious interpretation. Our in vivo and in vitro data show that these changes are consistent with ASA-induced displacement of T4 from its binding proteins and DPH-induced clearance of FT4.
Aspirin↗
[Implication on thyroid function tests].
We tried to investigate the present problems, concerning the reference individual and interval in thyroid function tests and find the solutions for them. We are now using healthy adults for the reference individual and interval. Recently, we found the sex-difference and age-related changes for reference individual and interval in free T3 measurement. We raised the questions on whether there are any sex-differences and/or age-related changes or not. Surprisingly, there were almost no detailed data about them especially in Japan. Therefore, we examined the Europe data, and found out some kind of sex-differences and age-related changes. We propose the following examinations using many Japanese population in order to provide a precise and proper reference individual and interval: 1. Whether there are any sex-difference in thyroid function tests? 2. Whether there are age-related change in thyroid function tests, for instance, simply dividing population into the immature, adult and the aged?
Adult↗
Prevalence of thyroid disease and abnormal thyroid function test results in patients with systemic lupus erythematosus.
Although thyroid disease has been associated with other autoimmune conditions, it is not well recognized in systemic lupus erythematosus (SLE) patients. We found that in 332 SLE patients hospitalized during a 5-year period, the overall prevalence of diagnosed thyroid disease (7.5%) was similar to that in other female populations, but the prevalence of diagnosed hypothyroidism (6.6%) was unexpectedly high. There was also a high frequency of abnormal thyroid function test results in 175 SLE patients without diagnosed thyroid disease who underwent laboratory screening. More than 45% of these patients had elevated levels of thyroid-stimulating hormone, 34% had low T3 determinations, and 18% had high antimicrosomal antibody titers. When patients were categorized into "functional groups," some showed evidence of the "euthyroid sick syndrome" (15%), but many more had laboratory test results suggestive of true (5%) or incipient (39%) primary hypothyroidism. We conclude that abnormal thyroid function test results are common in patients with SLE and that hypothyroidism, especially, should be considered when evaluating symptoms and signs in SLE patients.
Adolescent↗
Prevalence of abnormal thyroid function tests in a Down's syndrome population.
As thyroid function has been documented to be of a higher prevalence in individuals with Down's syndrome, a study was set up to assess the thyroid status of these individuals. Thyroid function tests (T.F.T.s) were initially reviewed on 100 individuals with Down's syndrome in the community and on 36 individuals who were residentially based. Abnormal T.F.T.s were then reviewed 3 yr later. In total sample of 136, initially 13 percent [n = 18] of individuals with Down's syndrome had abnormal T.F.T.s, 5 percent [n = 7] were established cases of thyroid disease and 8 percent [n = 11] were newly identified cases who had abnormal T.F.T.s. Three yr later 6.5 percent [n = 9] of the group who had had abnormal T.F.T.s continued to have abnormal T.F.T.s, 5 percent [n = 7] had thyroid disease and 1.5 percent [n = 2] still had biochemical evidence of thyroid dysfunction. There was a statistically significant increase in abnormal T.F.T.s in the residential sample compared to the community sample on both occasions. The incidence of thyroid dysfunction has been found to increase with age, particularly over the age of 40, however in this study the majority were under the age of 40 with an age range between 28.3 yr and 33.8 yr. The results in this study, coupled with the variability of T.F.T.s over time, highlights the need for regular monitoring of the thyroid status of individuals with Down's syndrome.
Adolescent↗
High prevalence of thyroid function test abnormalities in chronic schizophrenia.
The thyroid status of 249 patients with chronic schizophrenia (males = 136, females = 113) with a median age of 36 years (range: 16 to 58 years) and a median duration of hospitalisation of 10 years (range: 1 to 30 years) was assessed. Thyroid antibodies (TAb) were found in 51 patients (20%). In female patients, 32 (28%) were TAb positive compared to 13% (n = 152, p = 0.01) in healthy female blood donors. In male patients, the prevalence of TAb was 14% compared to 7% (n = 449, p = 0.01) in healthy male blood donors. Of the 183 patients who had thyroid hormone measurements, 60% had normal test, 5% had elevated TSH and 17% had low TSH. The T4, FT41 and FT31 were significantly lower in those with low or high TSH (p < 0.001) compared to those with normal TSH. Of the 143 patients with normal TSH, 33 (23%) had low T3. In conclusion, there is a spectrum of thyroid function test abnormalities in chronic schizophrenia; this may be related to an abnormality in the central regulation of the hypothalamo-pituitary thyroid axis as well as at the peripheral level. However the association between chronic schizophrenia and the presence of thyroid antibodies, and the clinical relevance of these biochemical abnormalities, are still not clear.
Adolescent↗
[Experimental and clinical evaluations of the effective thyroxine ratio by res-O-mat ETR test, a new in vitro thyroid function test].
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Evaluation Studies as Topic↗
Thyroid-stimulating immunoglobulins and thyroid function tests in two siblings with neonatal thyrotoxicosis.
Thyroid function and serum TSI levels in two siblings with neonatal thyrotoxicosis are described. The first infant was treated with exchange transfusion and potassium iodide. The second infant was treated with intrauterine propylthiouracil followed by potassium iodide. In contrast to the first infant, the second infant had no clinical sign of neonatal thyrotoxicosis. He also had lower TSI levels with a biological half-life of 5 days. Only one of three assays showed some TSI activity in breast milk.
Adult↗
Thyroid function tests in patients undergoing bone marrow transplantation.
Thyroid function was studied prospectively in 27 patients receiving bone marrow transplants to determine the effect of this procedure and its sequelae on serum thyroid hormone levels and thyrotropin secretion. Serum triiodothyronine and free triiodothyronine concentrations declined to subnormal levels in nearly all of the patients; free thyroxine concentration became subnormal in 15 patients. At the time of the nadir of the serum T3 concentration, serum thyrotropin concentration, measured by a sensitive immunoradiometric assay, declined significantly and became subnormal in nine patients. The data suggest that the reduction of serum thyroxine levels after transplantation is attributable, at least in part, to inhibition of thyrotropin secretion.
Adult↗
Thyroid physiology and thyroid function testing.
The art and science of medicine has changed so much in the last 40 years, not only in the manner that physicians treat medical diseases but also in how they diagnose them. Technological advances have made it possible to have a test for almost anything. These technological advances, however, are important contributing factors to the rising cost of healthcare. More than ever, cost containment is an important element in all aspects of patient care. Minimizing costly diagnostic imaging and laboratory tests is essential in keeping healthcare costs reasonable but these tests should not be excluded at the risk of compromising patient care. For patients with thyroid disorders, the multiplicity of tests available do not make diagnoses more accurate or treatment more effective. A single test, the sensitive thyrotropin assay, most eloquently allows an organized, streamlined approach to the diagnoses and management of patients with thyroid disease. Even the most technologically advanced tests that are available cannot replace the clinical skills of the physician. Clinical acumen combined with the judicious use of diagnostic testing is one of the most important elements in diagnosing and treating a patient.
Algorithms↗
Thyroid function tests. Selective use for cost containment.
Clinicians often obtain a variety of thyroid function tests in patients suspected of having thyroid disease when only a few are necessary to adequately establish a diagnosis and do follow-up. For hyperthyroidism and hypothyroidism, measurement of serum T4 is the best screening test. The serum T3 resin uptake test should be added with women suspected of being hyperthyroid because of the changes produced by pregnancy or estrogen-containing contraceptives. Various imaging techniques, including RAI, ultrasound, CT, and MRI, are often used for differentiating benign or cystic thyroid nodules from malignant or solid ones. Each of the available techniques has a different cost, and each is most suitable for a particular disorder. Special tests (eg, TRH testing and measurement of serum TBG) should be added to the basic screening tests only for questionable cases to differentiate diagnostic possibilities or confirm an uncertain diagnosis.
Cost Control↗
Case report: abnormal thyroid function tests in a patient and two normal volunteers treated with salsalate.
There are only three prior reports of abnormal thyroid function tests in patients who have received salsalate, the salicylate ester of salicylic acid. The authors report an elderly clinically euthyroid man who had thyroid function tests suggestive of central hypothyroidism while taking salsalate but whose thyroid tests returned to normal after the drug was discontinued. They also studied thyroid function tests, including free thyroxine (FT4) and reverse (T3), in two normal volunteers who took salsalate 750 mg twice daily for 1 week. In the normal subjects, total T4 and FT4 began to fall within 24 hours after the first dose of salsalate, and remained suppressed for at least 24 hours after the drug was discontinued. This rapidity of effect by salsalate is previously undescribed. There was also a fall in FT4, probably due to the use of diluted serum in the equilibrium dialysis FT4 assay. Because FT4 measurement using diluted serum or equilibrium dialysis may cause falsely low FT4 measurements, the authors believe ultrafiltration may be the only reliable method of measuring FT4 in these patients.
Aged↗
[Achilles tendon reflex time and a T3 test (Triosorb-Abbott) as thyroid function test criteria in endemic areas (with special reference to control findings following struma resection)].
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Achilles Tendon↗
Thyroid function tests in patients with acquired immune deficiency syndrome and healthy HIV1-positive out-patients.
The thyroid function tests as well as evidence of thyroiditis were studied in 18 male patients with acquired immune deficiency syndrome (AIDS) and 12 healthy HIV1-positive persons compared with an age-matched control group. Serum total thyroxine was not significantly different between the groups, but both serum total triiodothyronine, triiodothyronine uptake test, and free thyroid hormone indices showed significantly decreasing values from HIV1-positive healthy persons to AIDS patients compared with controls (P value from less than 0.05 to less 0.001). Serum TBG was elevated in HIV1-positive subjects and in patients with AIDS, with a significant inverse correlation with the T3-uptake test (Spearman's rho = 0.657, P less than 0.01). There was no correlation between thyroxine binding globulin and the other measured variables. The serum level of thyrotropine was not significantly different in the groups, whereas serum thyroglobulin was significantly lowered in the AIDS group. There was no correlation between thyroid function variables and survival time, hepatic function and ratio of T-helper to T-suppressor cells. No evidence of thyroiditis was observed. In conclusion thyroid tests showed an atypical outcome in HIV1-positive patients with or without AIDS compared with the pattern normally seen in non-thyroid illness, and should, therefore, caution the interpretation of the biochemical changes when diagnosing abnormal thyroid function in these patients.
Acquired Immunodeficiency Syndrome↗
Rational use of thyroid function tests.
In this era of cost containment, it is necessary to efficiently select the most important laboratory investigations for diagnostic and management purposes, with patient benefit as the ultimate objective. Thyroid function tests collectively represent a very costly item for laboratory services and have tended to be unselectively overutilized virtually until the present. Tests available for thyroid function testing include both in vitro and in vivo tests. Virtually all physicians are familiar with the free thyroxine (fT4) or its equivalents (fT4E), total and free triiodothyronine (TT3 and fT3), and sensitive thyrotrophin (TSH) assays, to which may be added plasma thyroglobulin (Tg), and thyroid autoantibodies (TAb) (including thyroid stimulating antibody [TSAb]). In vitro tests include thyroidal uptakes and scans, as well as other imaging techniques (e.g., ultrasound). Other less commonly used or obsolete techniques are not discussed. For screening or case finding where there is little probability that the patient(s) has thyroid dysfunction, a sensitive TSH assay is all that is initially required. If, however, the TSH result is elevated, a fT4E and TAb should then be performed. If the TSH is subnormal, then a fT4E, TT3, and (if still necessary) TSH response to TRH would determine if that patient was truly hyperthyroid (in elderly patients, a low TSH is often not associated with hyperthyroidism!). Conversely, not all patients with elevated fT4 are truly hyperthyroid. Uptakes and scans are primarily of importance in the correct diagnosis of unusual cases of hyperthyroidism and for nodular disease. When patients already diagnosed are being followed, proper selection of testing is again important, sometimes emphasizing one test over others (e.g., TT3); for example, in patients with Graves' Disease on anti-thyroid drugs, the fT4E and TSH values may not reflect the true status of the patient. On the one hand, the TSH may remain low for months after the patient has become euthyroid, and on the other hand, the fT4E may drop even below normal, whereas the T3 remains elevated (and the patient still hyperthyroid). The many other vagaries of these tests are also mentioned.
Autoantibodies↗
The effect of diltiazem on the manifestations of hyperthyroidism and thyroid function tests.
The aim of this study is to evaluate the effect of diltiazem on the symptoms and signs of hyperthyroidism and thyroid function tests and to assess whether diltiazem can be used associated with an anti-thyroid drug, propylthiouracil. Twenty-two patients with hyperthyroidism were included in a prospective, randomized and placebo controlled study. Group 1 (n:12) patients received diltiazem, 60 mg twice a day, for 30 days. Group 2 (n:10) patients received placebo for 30 days. The patients in both groups were given propylthiouracil, 100 mg three times a day, for the last 20 days of the study period. The patients remained in the hospital during the first 10 days. A standardized hyperthyroid symptom score (HSS) and thyroid function tests including thyroid-stimulating hormone (TSH), free thyroxine (free T4), free triiodothyronine (free T3), total thyroxine (T4) and total triiodothyronine (T3) were evaluated before and after 10 and 30 days of the study period. HSS decreased from 27.80 +/- 4.54 to 22.51 +/- 4.04 after 10 days of diltiazem therapy in Group 1 (p < 0.01). But there was no change in HSS in Group 2 (p > 0.01). No significant changes in thyroid function tests have occurred in both groups after 10 days of treatment. Diltiazem can be used in patients with hyperthyroidism to alleviate adrenergic manifestations. It can also be safely combined with propylthiouracil.
Antithyroid Agents↗
Subject-based reference values in thyroid function tests.
To evaluate the diagnostic value of subject-based reference values in thyroid function tests, we compared intra-individual and inter-individual variation. Five specimens were collected over a period of 2 weeks from each of 47 normal subjects, 29 women and 18 men, aged 20-47 yrs. T4, FT4, T3, and FT3 were assayed by RIA, and TSH by a sensitive immunoradiometric assay. One-way ANOVA for each test was statistically significant for a main subject effect, indicating that the subjects differed in their personal mean values for the thyroid function tests (T4, P < 0.01; FT4, P < 0.05; T3, P < 0.01; FT3, P < 0.05; TSH, P < 0.01). The ratio value (intra- over inter-individual variation) was T4, 0.41; FT4, 0.60; T3, 0.53; FT3, 0.63; TSH 0.36. The data indicate that conventional reference values are insensitive when compared to subject-based reference intervals in assessing the thyroid status of a given subject. Reactivity of the thyroid to the stimulation of endogenous TSH was assessed by the ratio delta FT 3/delta TSH in TRH stimulation tests. A positive correlation between basal FT3 and delta FT3/delta TSH (r = 0.566, P < 0.05) indicates that the thyroid with higher reactivity to TSH secretes more daily thyroid hormone. Negative correlation between basal TSH and delta FT3/delta TSH (r = -0.536, P < 0.05) means that a subject with lower reactivity of the thyroid needs a higher basal TSH level to compensate. The thyroid reactivity to TSH may be an important determinant for the individuality of the pituitary-thyroid axis.
Adult↗