Radioimmunological assays for triiodothyronine(T3) or thyroxine(T4) in sera containing antibodies against the hormones
✍ Scribed by Arne Vidnes; Terje Silsand
- Book ID
- 103038523
- Publisher
- Elsevier Science
- Year
- 1981
- Tongue
- English
- Weight
- 291 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0009-9120
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✦ Synopsis
For serum samples containing antibodies in vivo against triiodothyronine or thyroxine, the radioimmunoassays in use may give highly erroneous results. We wanted to compare the effects of two different radioimmunoassay systems on such sera, and to develop a suitable extraction procedure for use before such assays. Very different results were obtained with the use of single antibody or double antibody techniques on unextracted sera. The highest recoveries of total Ta and T4 from sera were found with two successive ethanol extractions.
ABNORMAL BINDING OF THYROID HORMONES to gamma globulins was first reported in 1956 (1) in patients with thyroid carcinoma. Later, similar binding of thyroxine and triiodothyronine was reported in some cases of Hashimoto's thyroiditis (2, 3), and also in primary hypothyroidism and hyperthyroidism (8). Abnormal binding of Ta and T 4 has also been reported in other cases , and in various animal species (3-7). Binding of T 3 to immunoglobulin G has also lately been demonstrated in this laboratory (unpublished).
These reports of the binding of T 3 and T 4 seem to indicate that abnormal binding of thyroid hormones happens more often than was previously believed.
The possibly misleading values obtained by radioimmunoassays on such sera indicate the need for a reliable method that eliminates the interference caused by the antibodies during the assay. Some attempts have been made to investigate the total T 3 or T 4 concentrations when binding to gamma globulin fractions has occurred (9, 10, 11), but we found these methods difficult to reproduce.
Our intention is to show the different values obtained with antibody-containing sera against T 3 using two radioimmunoassay systems, and to investigate the ability of different procedures to extract T a before a radioimmunoassay.
MATERIALS AND M ETHODS
Methods Without Extraction
Single-antibody radioimmunoassay for T3 or T4 was performed using kits from Behringwerke AG, Radiochemical Laboratory, Germany, These kits employ the antibody in solution, and the separation of the labelled free and bound hormone is performed by adding polyethylene glycol to a final concentration of approximately 20%. The precipitates are counted after centrifugation.