Interpretation of Thyroid function tests. conversion of thyroxine,. proteins resulting in lowish free T4 in the presence of normal thyroid.
Make sure you find out your lab's normal ranges and review these with your doctor.
1 Department of Pathology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada 2 Department of Medicine, University of Ottawa, Ottawa Civic Hospital, Ottawa, Ontario, Canada. Received, Accepted 10 November 1986, Available online We describe a sensitive thyrotropin (TSH) assay in the evaluation of thyroxine replacement therapy.
7 The ratio of T3 to T4 is generally higher in patients with Graves' disease versus patients with thyroiditis or iodide-induced thyrotoxicosis. 8 Moreover, a ratio of 20 ng/mg during antithyroid therapy for Graves' disease may indicate remission is less likely.
Free thyroxine (free T4). TSH and free T4 are regularly checked to assure that the right dose of thyroid hormone is being given to make TSH normal.
Diminished peripheral conversion of T4 to T3 contributes to low serum-T3 levels. T3 levels are low in only 50 of hypothyroid patients. Relatively more T3 than T4 is produced as the thyroid fails.
The levels are high in approximately 90 of hyperthyroid patients and low in approximately 85 of hypothyroid patients. 2. Measurement and Estimation of Free-T4 Level. Free - T 4 level can be estimated by several different methods.
Free Thyroxine (FT4) and Free Triiodothyronine (FT3). The hormone-analog methods were principally engineered to give normal FT4 values in high TBG states.
Thyroid-stimulating hormone testing is the preferred approach because: 1) TSH is central to the negative-feedback system; 2) small changes in serum thyroid function cause logarithmic amplification in TSH secretion; and (3) the most advanced (third-generation) chemiluminescent TSH assays can now detect both elevation and significant lowering of TSH levels, and are capable of reliably measuring.
If you had a low reading, and a high TSH, your doctor might consider that indicative of hypothyroidism. If your doctor ran a test called Total T4 or Total Thyroxine, normal range is approximately 4.5 to 12.5.
In patients with central hypothyroidism, regulation of T4 replacement may need estimations of free-T4 levels, since TSH levels may be less reliable. Total Serum T4 Level Total serum T4 level, measured by radioimmunoassay, has high sensitivity in reflecting the functional state of most patients with thyroid disease.
The main purpose of free-T4 and free-T3 assays is to distinguish reliably between thyrotoxicosis, hypothyroidism, and the euthyroid state. This objective that cannot be attained with assays of total-T4 and T3 because of hereditary and acquired variations in the concentrations of binding proteins.
Patients taking varying amounts of L-thyroxine replacement doses were studied using a thyrotropin-releasing hormone (TRH) test and a sensitive TSH assay as the indices of optimal replacement therapy. There were no differences in the mean thyroxine doses of those patients who had a normal TRH response and those who had a flat response.
Because of TBG level abnormalities, which require T3RU for clarification, many laboratories routinely check both total-T4 level and T3RU, and report the result as the FTI. 3 Many factors can increase T4 levels in the absence of a hyperthyroid state.
However, serum TSH values, as measured by a sensitive TSH3 MAIACLONE (Serono) immunoradiometric method, were subnormal in all patients with flat TRH responses. The TSH (Serono) assay provided the best single blood test of optimal thyroxine replacement.
Value of free thyroxine (FT 4 free triiodothyronine (FT 3. 7 of the 14 patients had normal FT4 values and 7 had values above the normal range).
Review your test results with the doctor. Normal range is approximately 0.5 to 5.5. (As of Spring 2003, many experts are calling for the range to be revised to.3 to 3.0) If the TSH level is at the higher end of the range, or above the range, your doctor may determine that you are hypothyroid.
Or alternative physician for further interpretation and diagnosis. Tips: Many people who have radioactive iodine treatment for hyperthyroidism/Graves' Disease, or who have sugery to remove all or part of the thyroid due to nodules or cancer, are hypothyroid.