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Thyroid function tests in patients undergoing maintenance dialysis: characterization of the 'low-T4 syndrome' in subjects on regular hemodialysis and continuous ambulatory peritoneal dialysis.
Thyroid function tests were evaluated in 38 patients on regular hemodialysis (HD), in 36 on continuous ambulatory peritoneal dialysis (CAPD) and in 39 healthy controls. A significant reduction in total thyroxine (TT4), total triiodothyronine (TT3), reverse (rT3), and free T4 (fT4) mean levels and normal TSH, free T3, TBG and albumin concentrations was found in both HD and CAPD patients. A 'low-T4 syndrome' (serum T4 less than 5 micrograms/dl) was found in 9 CAPD (25%) and 20 HD (53%) patients, but none of them had fT4 levels below the normal laboratory range. The only striking difference between low-T4 HD and low-T4 CAPD patients was the significantly lower TBG and albumin serum levels in CAPD group. Low-T4 HD displayed normal TBG levels but enhanced fT4/TT4 and fT4/TT4 X TBG ratios. We concluded that: the abnormalities in thyroid function tests in patients on long-term dialysis (HD and CAPD) do not express the existence of a true hypothyroidism; a different pathogenesis of the low-T4 syndrome in the CAPD and HD groups may be hypothesized: in the former it could be attributed to a reduction in serum-binding capacity for thyroid hormones, in the latter the relative increase in fT4 percentage despite normal TBG levels suggests either the presence of T4-TBG-binding inhibitor(s), or structural abnormalities of thyroid-hormone-binding proteins.
Thyroid function tests in chronic liver disease: evidence for multiple abnormalities despite clinical euthyroidism.
To further evaluate thyroid function in patients with liver disease, we have measured total and free T3 and T4, thyroxine binding globulin, basal and thyrotropin releasing hormone-stimulated thyrotropin and thyroglobulin antibodies in 33 patients with liver cirrhosis, in 22 with chronic hepatitis and in 30 healthy controls. All the patients but one were clinically euthyroid. T3, FT3, T3/thyroxine binding globulin and T4/thyroxine binding globulin ratios and thyrotropin after thyrotropin releasing hormone were significantly reduced, while FT4, thyroxine binding globulin and thyrotropin were significantly increased in liver cirrhosis. In chronic hepatitis group, FT3 and T3/thyroxine binding globulin ratio were significantly lower and thyroxine binding globulin and FT4 were higher than in healthy controls. The between patients comparison revealed a significantly lower T3, FT3, T3/thyroxine binding globulin and T4/thyroxine binding globulin ratios and delta thyrotropin in cirrhotics. Thyroglobulin antibodies were present at high titre only in two patients one of whom having evidence of Hashimoto's thyroiditis with subclinical hypothyroidism. The correlation coefficient between T4/thyroxine binding globulin ratio and FT4 were lower in patients than in controls. Furthermore an abnormal thyrotropin response to thyrotropin releasing hormone was shown in 10 cirrhotics and in four patients with chronic hepatitis. Serum T3 significantly correlated with serum bilirubin, albumin, and prothrombin time in both groups of patients. The present data confirm the existence of several abnormalities of thyroid function tests in patients with chronic liver disease, although showing that euthyroidism is almost always maintained, probably as a result of low-normal FT3 and high-normal FT4. Furthermore, T3 serum levels appear to parallel the severity of liver dysfunction.
[USE OF THYROID FUNCTION TESTS IN MODERN DIAGNOSTIC PRACTICES].
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Limitations of new thyroid function tests in pregnancy.
Sensitive immunoradiometric assays (IRMA) for TSH and radioimmunoassay (RIA) kits for free thyroid hormones (fT4, fT3) are becoming increasingly used for routine thyroid investigations. We have assessed these tests in 93 euthyroid pregnant women. Mean fT4 and fT3 values decreased with gestation by 24-27% and 14-35%, respectively, using several analogue RIA kits. Some patients had free hormone values which fell below the reference range derived from non-pregnant euthyroid patients. By contrast, the fT4 concentrations measured by direct equilibrium dialysis fell by only 16% with all values within the reference range. Serum non-esterified fatty acid (NEFA) levels (non-fasting) did not correlate with fT4 and fT3 but a spurious effect of serum albumin levels on the free hormone kits was suggested. TSH results showed that the majority of subjects had lower values measured by IRMA than by RIA. Three patients had basal TSH (IRMA) below the mean detection limit of the assay; this could have been falsely interpreted as indicating hyperthyroidism. We conclude that, as with longer established thyroid function tests, special care must be taken in interpreting results of these new thyroid function tests in pregnancy.
Evaluation of patients with mildly abnormal thyroid function tests.
Subclinical hypothyroidism, subclinical hyperthyroidism and the sick euthyroid syndrome are three conditions that can be effectively assessed using newer tests. Subclinical hypothyroidism is defined as an elevated sensitive thyrotropin level with a normal free thyroxine level. Replacement therapy with levothyroxine is recommended for patients who have a serum thyrotropin level over 20 microU mL (20 mU per L), patients with thyroid antimicrosomal antibodies, or patients with goiter. A diagnosis of subclinical hyperthyroidism is made when a suppressed serum thyrotropin level occurs in association with normal free thyroxine and triiodothyronine levels. The optimal management of these patients is still under investigation. Close follow-up is necessary to monitor for the possible development of overt hyperthyroidism, tachyarrhythmias or osteoporosis. Critically ill patients with the sick euthyroid syndrome have a wide variety of abnormal results on thyroid function testing. These aberrations are most often related to the underlying disease rather than a primary thyroid disorder.
[Value of the thiocyanate test in the plateau curves of thyroid disorders (thyrosis and hyperthyroidism) during the thyroid function test by radioactive iodine].
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[Effect of various iodine-containing compounds on thyroid function tests. 1. 24-hour 131 I uptake of the thyroid gland].
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[Evaluation in cardiopathic patients of the diagnostic significance of the test of triiodothyronine inhibition of iodine uptake by the thyroid gland as a thyroid function test].
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Comparison of Kodak Amerlite FT4 and TSH-30 with T4 and TSH as first-line thyroid function tests.
OBJECTIVES: To evaluate the effect of test automation and a change in strategy for thyroid function tests (TFT) on personnel needs and turn-around time. The first-line TFT were changed from T4 and TSH to FT4 and TSH-30. DESIGN AND METHODS: Samples received for TFT from 357 randomly selected patients were analyzed by RIA for T4, and by IRMA for TSH as first-line tests. FT3 and TBG were requested as back-up tests when indicated. Patients were classified on the basis of these results and the clinical information received. All the samples were reanalyzed for FT4 and TSH on the Amerlite Processing Center, which is a batch, semiautomated immunoassay system. The thyroid status of the patients was compared using the two protocols and available clinical data. RESULTS: There was good correlation between TSH-IRMA and TSH-30 in the 160 patients classified as euthyroid (r = 0.956; p < 0.001) and no euthyroid patient was reclassified with the new strategy. In 21 patients with borderline raised TSH-IRMA, FT4 was found to be low in only 2. All 11 patients classified as hypothyroid had TSH results greater than 10 mU/L and all except 2 patients had FT4 less than 11 nmol/L. The status of 21 hyperthyroid as well as 40 patients on carbimazole could be determined biochemically on the basis of agreement between both the FT4 and TSH-30 results. FT3 was only required if the FT4 and TSH-30 results were not in agreement. In 42 patients on T4 therapy, adequacy of replacement was assessed better using FT4 and TSH-30. No patient required backup testing with TBG to determine thyroid status using the new testing protocol. The change in TFT protocol reduced the 95% turn-around time from 3 days to 1 day. CONCLUSION: The introduction of FT4 and TSH-30 as first-line TFT improved the turn-around time for TFT, resulted in 25% reduction in personnel requirements, 60% reduction in FT3 assays, and discontinuation of TBG assay.
A prospective critical evaluation of in vitro thyroid function tests.
A number of 2 325 serum samples from a population of in- and outpatients were collected during a six-month period in order to evaluate the usefulness of various thyroid function tests in the clinical laboratory routine. The samples were analysed with the following thyroid function tests: total triiodothyronine (T3) (TT3), total thyroxine (T4) (TT4), free T3 index (FT3I), free T4 index (FT4I) and thyrotropin (TSH). One to two years after the primary evaluation, a follow-up was performed and the final diagnoses were checked in the patients' records. The values of these parameters in the diagnosis of hyperthyroidism were: FT3I greater than FT4I greater than TT3 greater than TT4. The corresponding results in the diagnosis of hypothyroidism were: TSH greater than FT4I greater than FT3I = TT3. No single test could detect both hyper- and hypothyroidism effectively. The only one-step strategy for thyroid evaluation in patients without apparent clinical signs of hyper- or hypothyroidism would therefore be the combined determination of T3 and TSH. The study also showed distinct differences between the reference values of the healthy population and patients without thyroid disorders.
[A critique of modern thyroid function tests].
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THYROID FUNCTION TESTS.
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Evaluation of the profile of alopecia areata and the prevalence of thyroid function test abnormalities and serum autoantibodies in Iranian patients.
BACKGROUND: The study aimed at evaluating the prevalence of thyroid function abnormalities in patients with alopecia areata (AA) and its association with other autoimmune diseases and various autoimmune antibodies. METHOD: We retrospectively analyzed medical records of 123 patients with AA. The main site of involvement, pattern, and extent of alopecia as well as presence of the similar disease in first-degree family members and serologic status of patients were recorded. RESULTS: Participating in the study were 57 males and 66 females (6 to 59 years old). In the majority of patients (69.9%) the disease was manifested in the first two decades of life. Patients with family members having alopecia were recorded in 24.4%. Thyroid function abnormalities were found in 8.9% of patients. Positive autoimmune antibodies were associated with AA in 51.4% of patients with no significant association between the severity and duration of disease and presence of these antibodies. CONCLUSION: The incidence of positive auto-immune antibodies in Iranian patients is higher than previous reports. Concerning the female:male ratio, thyroid function tests and the prevalence of alopecia in first-degree relatives, our results are compatible with previous data obtained from different ethnic populations. Previous reports documented that a greater severity and longer duration of AA were seen in the early onset forms; however our result are relatively different which could be explained by differences in genetic factors.
Abnormalities in thyroid function tests in patients admitted to medical service.
Serum thyroid hormone, thyrotropin (TSH) and thyroxine-binding globulin (TBG) concentrations, free thyroxine index values, and free thyroxine concentrations were measured at the time of admission in all 77 patients hospitalized on a medical service on four separate days. Serum thyroxine (T4) concentrations and serum free T4 index values were decreased in 19.5% and 11.7%, respectively, and increased in 3.9% and 11.7%, respectively; serum free T4 concentrations were decreased in 6.8% and increased in 5.4%. Six patients (7.8%) had increased serum TSH concentrations. Serum triiodothyronine (T3) concentrations were decreased in 26.0% and reverse triiodothyronine (rT3) concentrations were increased in 29.9%. None had manifestations of thyroid disease. These results indicate that available thyroid function tests may give misleading results in patients with nonthyroid illness and suggest that caution be exercised in diagnosing thyroid disease in hospitalized patients.
Thyroid function tests. Tests must still be done in possible thyroid dysfunction.
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[The effect of age on in vitro thyroid function tests in adult patients on a chronic hemodialysis program].
The research was designed to investigate in vitro thyroid function tests (TT4, TT3, FT4, FT3, rT3 and TBG) in 14 patients on regular haemodialysis (RHD) and 15 healthy, euthyroid subjects aged 40-59 years and in 17 patients on RHD and 14 subjects aged 60 years and more. Group of older subjects had significantly lower (p less than or equal to 0.01) levels of TT4, TT3 and TBG than group of younger, but those differences were lost between patient groups. Group of older patients had significantly lower level of FT3 than group of younger. Both groups of patients had significantly lower levels of TT3, FT4 and FT3 than both control groups and there was no significant difference in rT3 levels. Age structure markedly influenced difference in TT4 levels and there was also some influence on TBG level. Serum TT4 concentration was significantly lower in both patient groups than in younger subjects group but similar to the level in group of older subjects. The only difference in TBG levels between four groups was significantly lower (p less than or equal to 0.05) TBG level in group of younger patients than in group of younger subjects.