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At least 19 recordsLinked to original sources
PubMed1979

Abnormal thyroid function tests in devere non-thyroidal illness: diagnostic and pathophysiologic aspects.

In vitro thyroid function tests were studied in twenty-three patients with serious non-thyroidal illness. All had reduced protein binding of serum thyroxine (T4) and serum triiodothyronine (T3) as reflected in increased T4 and T3 uptake tests. The mean T4-binding prealbumin (TBPA) capacity and concentration were about one third the normal levels, whereas the decrease in R4-binding globulin (TBG) was much smaller. Increased serum free fatty acids and reverse T3 were frequently observed, but in vitro displacement of thyroid hormones from their binding sites was achieved only with much high concentrations of these compounds. Other still unrecognized substances significantly inhibiting binding of thyroid hormones might, however, occur in sera of severely ill patients. Evidence in favour of this possibility was the disproportionately high serum T4 by TBG-binding assay relative to T4 by radioimmunoassay. In most of the patients the dual-stage free T4 was elevated, whereas the single-stage free T4 index (CT4I) was within the reference interval. However, neither of these indices reflected the moderately increased dialysable free T4 concentration very accurately. The free T3 index was depressed in most of the patients, whereas the dialysable free T3 concentration was not affected. For practical purposes the combination of normal serum T4 and CT4I in a severely ill patient indicates absence of an associated thyrometabolic disorders.

Adult↗
PubMed1978

[Sex hormone binding globulin (SHBG), a new metabolic in vitro thyroid function test].

SHBG (sex hormone binding globulin) is a carrier protein for the sex hormones testosterone and estradiol with a molecular weight of about 95000 dalton. It can be used as a metabolic test of thyroid function. SHBG was measured by the adsorption method of Mickelson and Petra; the SHBG contained in serum is incubated with 3H-5alpha-dihydrotestosterone and adsorbed to a cellulose filter. Thirty-eight female patients with hyperthyroidism before treatment had markedly elevated levels of SHBG (x +/- SD: 4.85 +/- 2.4 microgram DHT/100 ml) compared with normal controls (1.50 +/- 0.57; p is less than 0.001). A good correlation between the thyroid hormones and SHBG could be domonstrated which was better for T3 than for T4:r =0.76 (p is less than 0.001) for T3 and r= 0.65 (p is less than 0.001) for T4. This agrees with the clinical finding that the circulating T3 level is a better index of the metabolic severity of thyrotoxicosis than T4. After radioiodine treatment SHBG returns to normal values in euthyroid patients (1.38 +/- 0.8; n = 15) and remains elevated in persistent hyperthyroidism (3.99 +/-1,6; n = 67). Even in patients with persistent biochemical hyperthyroidism who are completely euthyroid on clinical examination, SHBG remains high. Despite lack of evidence of clinical hyperthyroidism, this metabolic test demonstrates the biologic significance of merely biochemical hyperthyroidism. Estimation of SHBG as a metabolic thyroid function test in vitro is of special value for the evaluation of patients showing discrepancies between the clinical and biochemical states and for borderline hyperthyroidism.

Carrier Proteins↗
PubMed1979

Simple, rapid thyroid function testing with 99mTc-pertechnetate thyroid uptake ratio and neck/thigh ratio.

To avoid the technical difficulties and errors inherent in the measurement of early thyroid uptake of 99mTcO4-,techniques which are independent of absolute uptake, neck extrathyroidal background and dose standards were evaluated in a series of 108 patients. After intravenous injection of 2 mCi 99mTcO4-, radioactivity was recorded over the neck and thigh. Thyroid uptake ratios were calculated as the ratios of activity over the neck at two times. A neck/thigh ratio was calculated from the recorded activities at 15 min after injection. Examination of these parameters showed that a combination of the 15 min neck/thigh ratio and the 10'/2' thyroid uptake ratio best served to discriminate thyroid function: 92% of hyperthyroid cases were correctly identified by a neck/thigh ratio above 4.7 and 95% of hypothyroid cases were identified by the combination of a neck/thigh ratio below 3 and a 10'/2' thyroid uptake ratio below 1. Correct classification of euthyroidism was 84% but with the exclusion of patients previously treated with 131I, this rose to 91%. The accuracy of the 99mTc procedure is comparable to that of the standard 24 hr 131I uptake run concurrently in this series and duplicates the accuracy of computer assisted determinations of absolute thyroid 99mTcO4- uptakes. The procedure provides a convenient method for the evaluation of thyroid function as an accompaniment to 99mTcO4- thyroid imaging.

Humans↗
PubMed1977

The practical use of thyroid function tests.

The diagnosis of thyroid disorders can usually be established by two tests: the serum T4 and the resin T3 uptake (RT3U). The T4 test measures both free and bound thyroxine; the RT3U reflects the number of binding sites available on thyroid-binding globulin. The values of these two tests can be used to calculate a free thyroxine index (FTI), which gives an approximation of the free T4 in the serum. Measurement of thyroid-stimulating hormone (TSH) is useful for the diagnosis of hypothyroidism, while the thyrotropin-releasing hormone (TRH) test may facilitate diagnosis of hyperthyroidism.

Female↗
PubMed1978

Thyroid function tests in adults with Down's syndrome.

Thyroid status was studied in 24 patients above the age of 40 years with Down's syndrome. Three patients had thyroid function tests indicating hypothyroidism. Eight patients had thyroid autoantibodies in serum and 8 patients had a higher than normal level of thyroid stimulating hormone in serum. None of the patients had figures indicating thyrotoxicosis. None of the patients showed any of the clinical signs usually seen in patients with hypothyroidism. It is concluded that biochemical tests indicating hypothyroidism are much more often seen in patients with Down's syndrome than in normal subjects and that thyroid status should be assessed in old patients with this disease.

Adult↗
PubMed1977

Testing thyroid function.

From the foregoing discussion, it is clear that no single test provides sufficient information to justify its use alone as a single screening test. In vitro tests have now replaced in vivo procedures in the vast majority of patients. Because of the frequency of abnormalities in TBP concentration, the estimation of total T4 should be accompanied by a T3 resin uptake to provide the free thyroxine index or alternatively, a normalized T4 test (Quantisorb or ETR) is preferable. In patients with suspected hyperthyroidism, the initial laboratory evaluation should be an estimate of free T4 and a total serum T3 determination. Whereas the majority of hyperthyroid patients exhibit elevated free T4 levels, a smaller but variable percentage will exhibit only an elevated T3 level. The diagnosis mients where equivocal tests do not provide a diagnosis. In patients with suspected hypothyroidism, estimations of T4 and T3 provide evidence of diminished thyroidal secretion. The diagnosis should be confirmed by demonstration of an elevated TSH level. Normal or low TSH levels point to a diagnosis of pituitary hypothyroidism which can be confirmed by TRH stimulation. The finding of low normal or subnormal T4, normal T3 and elevated TSH levels suggest "compensated hypothyroidism". Estimation of thyroid autoantibodies may confirm the diagnosis of autoimmune thyroiditis. It is emphasized that the approach to testing thyroid function should be an adequate clinical assessment so that selection of the appropriate test(s) currently available leads to a diagnosis of great certainty in most cases.

Autoantibodies↗
PubMed1978

Thyroid function tests in patients on long-term treatment with various anticonvulsant drugs.

Thyroid function tests were studied in patients undergoing long-term treatment with various anticonvulsant drugs. Previous reports that diphenylhydantoin induces a decrease in the serum concentrations of total and free thyroxine (T4) and triiodothyronine (T3) without a change in the TSH concentration were confirmed. Diphenylhydantoin had no effect on reverse T3. Carbamazepine was also found to decrease serum T4, the free T4 index and T3 but, with the exception of T3, the decrease was smaller than that induced by diphenylhydantoin. Dipropylacetic acid did not influence the serum thyroid hormone concentrations, and neither did primidone. This demonstrates that the interaction between anticonvulsant drugs of different chemical structure and thyroid hormone metabolism is diverse. None of the drugs tested altered serum TSH or the T3 uptake test for the estimation of unsaturated thyroid hormone binding-capacity in serum. These two tests are considered diagnostically more dependable than the measurement of thyroid hormones in serum when diphenylhydantoin and carbamazepine are administered.

Adolescent↗
PubMed1975

[Correlation studies of some thyroid function tests (author's transl)].

The results of a thyroid test based on ion exchange and column chromatographic separation and of two radiochemical T4 and three T3 tests were carried out with commercially available reagent packs ready for use, and were compared with the PBI values found in the same serum sample in each case. This also tested the analytical precision of each method. A good correlation was found between the PBI and the T4 values, while the accuracy of the T3 tests was unsatisfactory.

Autoanalysis↗