This assay has been designated to minimize interference from heterophilic antibodies.In: Klee. GG, ed. Clinics in Laboratory Medicine: Pathophysiology of Thyroid Disease. Philadelphia, PA: W.B. Saunders Company;. Ross DS. Subclinical hyperthyroidism: possible danger for overzealous thyroxine replacement therapy. Mayo Clin Proc.
Substance Test Concentration SI Units Carbamazepine 12 mg/dL 508 mol/L Furosemide 2 mg/dL 61 mol/L. Ibuprophen 10 mg/dL 484 mol/L Phenytoin 10 mg/dL 396 mol/L Salicylic acid 50 g/mL 3.62 mmol/L Valproic acid 50 mg/dL 3467 mol/L Patient samples may contain heterophilic antibodies that could react in immunoassays to give falsely elevated or depressed results.Romijn JA, Wiersinga WM. Decreased nocturnal surge of thyrotropin in nonthyroidal illness. J Clin Endocrinol Metab. 1990;. Chopra IJ. Nonthyroidal illness syndrome or euthyroid sick syndrome? Endocr Pract. 1996;.
Clin Chem. 1996;. Faglia G, Beck-Peccoz P, Piscitelli G, et al. Inappropriate secretion of thyrotropin by the pituitary. Horm Res. 1987;. Ohzeki T, Hanaki K, Motozumi H, et al. Refractoriness at peripheral and pituitary receptors in general and pituitary types of thyroid hormone resistance.Clin Chem. 1996;. Uy HL, Reasner CA, Samuels MH. Pattern of recovery of the hypothalamic-pituitary-thyroid axis following radioactive iodine therapy in patients with Graves disease. Am J Med. 1995;. Davis JRE, Black EG, Sheppard MC.
1998;. Lamberg BA, Helenius T, Liewendahl K. Assessment of thyroxine suppression in thyroid carcinoma patients with a sensitive immunoradiometric TSH assay. Clin Endocrinol. 1986;. Braverman LE. Evaluation of thyroid status in patients with thyrotoxicosis.It regulates the bodys rate of metabolism and is necessary for normal growth and development. Clinical Significance: High values are usually due to excessive T4 production, called hyperthyroidism. Low values usually indicate too little T4 is being produced by the thyroid gland, called hypothyroidism.
Reference Range: Stability: Temperatures. Period Room Temperature 24 Hours Refrigerated (2-8 C) 14 Days Frozen (-20 C) 30 Days Avoid repeated freezing and thawing. Use: Thyroxine (T4) is the primary hormone secreted by the thyroid gland.Am J Med. 1986;. Hamblin PS, Dyer SA, Mohr VS, et al. Relationship between thyrotropin and thyroxine changes during recovery from severe hypothyroxinemia of critical illness. J Clin Endocrinol Metab. 1986;.
Clin Chem. 1996;. Ridgway EC. Modern concepts of primary thyroid gland failure. Clin Chem. 1996;. Nicoloff JT, Spencer CA. The use and misuse of the sensitive thyrotropin assays. J Clin Endocrinol Metab.In subjects aged 13-18 years the mean fT4 concentration was higher and the mean fT3 concentration lower than in children aged 0-12 years. The reasons for these differences are not known, but the data obtained provide a useful guide to the interpretation of serum free thyroid hormone measurements in children.
Horm Metab Res. 1992;. Refetoff S, Weiss RE, Usala SJ. The syndromes of resistance to thyroid hormone. Endocr Rev. 1993;. Brent GA, Hershman JM, Braunstein GD. Patients with severe nonthyroidal illness and serum thyrotropin concentrations in the hypothyroid range.Treatment is often thyroid medication. Causes for Rejection: Citrate plasma specimen; improper labeling. Interfering Substances : The following substances can cause elevated FT4 results by releasing T4 from serum binding protein.
1990;. Spencer CA, LoPresti JS, Patel A, et al. Applications of a new chemiluminometric TSH assay to subnormal assessment. J Clin Endocrinol Metab. 1990;. Kaptein EM. Clinical application of free thyroxine determinations.Evalulation of a sensitive chemiluminescent assay for TSH in the follow-up of treated thyrotoxicosis. Clin Endocrinol. 1987;. Spencer CA, Takeuchi M, Kazarosyan M. Current status and performance goals for serum thyrotropin (TSH) assays.
Serum free thyroxine (fT4) and free tri-iodothyronine (fT3) were measured in 138 normal school children, adolescents and their younger siblings, whose ages ranged from 3 months to 18 years. Mean fT4 concentration (16.8 pmol/L) was similar to the adult mean concentration of 17 pmol/L and all the values were within the adult reference range.Specimen should be free of particulate matter. To prevent the appearance of fibrin in serum samples, complete clot formation should take place before centrifugation. If clotting time is increased due to thrombolytic or anticoagulant therapy, the use of plasma specimen will allow for faster sample processing and reduce the risk of particulate matter.
Thyroxine and thyroid stimulating hormone tests may be ordered in a patient has a goiter or if a woman is experiencing infertility. The free thyroxine test is not ordered as a lone blood test.At all ages the fT3 range was considerably higher than the adult reference range and the overall mean fT3 concentration (8.3 pmol/L) was at the upper limit of normal in adults.
Free Thyroxine (FT4) CPT Code: 84439 Specimen: Serum or heparinized plasma Volume: 0.8 mL. Minimum Volume: 0.3 mL (Note: This volume does not allow for repeat testing.) Container: Red-top tube or gel-barrier tube Methodology: Immunoassay Collection: If a red-top tube is used, transfer separated serum to a plastic transport tube.Blood collected in the presence of oxalate potentially can cause clumping of chrome particles and should not be used. Frozen plasma samples with insufficient anticoagulants potentially can cause clumping of chrome particles and should not be used.
Pregnancy Trimester Two: 0.6 to 1 ng/dL or 7.7 to 12.9 pmol/L. Pregnancy Trimester Three: 0.5 to 0.8 ng/dL or 6.4 to 10.3 pmol/L Laboratory Values During Pregnancy.What is Free Thyroxine? Thyroxine blood tests are typically ordered to evaluate thyroid health. Until recently, total thyroxine levels were used to diagnose thyroid disorders like hypothyroidism or hyperthyroidism, but free thyroxine levels are unaffected by protein bonds, so the test gives doctors a more accurate idea of how well the thyroid is functioning.
Typically, doctors will order other tests to gauge thyroid or reproductive health. Normal Value Range Negative Pregnancy Adult: 0.8 to 1.7 ng/dL or 10.3 to 21.9 pmol/L. Pregnancy Trimester One: 0.8 to 1.2 ng/dL or 10.3 to 15.5 pmol/L.Nelson JC, Clark SJ, Borut DL, et al. Age related changes in serum free thyroxine during childhood and adolescence. J Pediatr. 1993;. Fisher DA. Physiological variations in thyroid hormones; physiological and pathophysiological considerations.
". Les symptmes peuvent tre des palpitations, une hypernervosit, parce qu'ils pourraient tre en hyperthyrodie. La firme a expriment cela, mais ce sont des cas trs rares. Par contre il faudra souvent rduire la dose ".Action Synthetic form of thyroxine that replaces endogenous thyroxine, increasing thyroid hormone levels. Thyroid hormones help regulate cell growth and differentiation and increase metabolism of lipids, protein, and carbohydrates. Availability Powder for injection: 200 mcg/vial in 6- and 10-ml vials, 500 mcg/vial in 6- and 10-ml vials.
Administration of levothyroxine sodium alone will result in complete physiologic thyroid replacement. Canine hypothyroidism is usually primary, i.e., due to atrophy of the thyroid gland. In the majority of cases the atrophy is associated with lymphocytic thyroiditis and in the remainder it is noninflammatory and as of yet unknown etiology.Although the pathogenesis of thyroid nodules and sporadic nontoxic multinodular goiters is poorly understood, TSH is presumed to be necessary if not sufficient and, therefore, suppression of TSH secretion might be expected to result in a decrease in nodule or goiter size or at least prevent further enlargement.