Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Clinical evaluation of free thyroxine calculation from thyroxine and thyroxine binding globulin radioimmunoassays


Free T4 calculation was performed based on the equation of the law of mass action between T4 and TBG assessed by routine radioimmunoassay. To examine the validity of this calculation, sera from normal subjects, from hypo- and hyperthyroid patients, from subjects with hereditary deficiency or increase in TBG, and those from uncomplicated pregancy were included in the assay and the results were compared with those directly measured by radioimmunoassay with encapsulated antibody. Free T4 calculation on the sera described above was almost equal to the free T4 concentration measured directly and reflected clinical thyroid states. Thus, the proposed equation for the calculation of free T4 from total T4 and TBG radioimmunoassay is useful for clinical purposes as well as direct free T4 radioimmunoassay.

This is a preview of subscription content, log in to check access.


  1. Burr WA, Ramsden DB, Evans SE, Hogan T, Hoffenberg R (1977) Concentration of thyroxine-binding globulin: value of direct assay. Br Med J 1:485–488

  2. Burr WA, Evans SE, Lee J, Prince HP, Ramsden DB (1979) The ratio of thyroxine to thyroxine-binding globulin in the assessment of thyroid function. Clin Endocrinol (Oxf) 11:333–342

  3. Clark E, Horn DB (1965) Assessment of thyroid function by the combined use of the serum protein-bound iodine and resin uptake of 131I-triiodothyronine. J Clin Endocrinol Metab 25:39–45

  4. Elzinga KE, Carr EA, Beierwaltes WH (1961) Adaptation of the standard durrum-type cell for reverse-flow paper electrophoresis. Am J Clin Pathol 36:125–131

  5. Faden VB, Rodbard D (1975) Radioimmunoassay data processing, National Technical Information Service, Springfield, USA

  6. Grimm W, Buhrer E, Ziegler R, Schonberger W (1978) Die Ermittlung des FT-4-Wertes durch Rechnung oder Nomogramm, eine Alternative zur AFT-4-Bestimmung. In: Radioaktive Isotope in Klinik und Forschung 13, Band, 2 Teil, eds by Hofer et al, Verlag Eggermann, Wien

  7. Hamada S, Nakagawa T, Mori T, Torizuka K (1970) Re-evaluation of thyroxine binding and free thyroxine in human serum by paper electrophoresis and equilibrium dialysis, and a new free thyroxine index. J Clin Endocrinol Metab 31:166–179

  8. Hamada S, Kosaka T, Torizuka K (1975) Clinical evaluation of new indicators of free thyroxine concentration and thyroxinebinding globulin capacity. Clin Chim Acta 63:129–137

  9. Kaptein EM, McIntyre SS, Weiner JM, Spencer CA, Nicoloff JT (1981) Free thyroxine estimates in non-thyroidal illness: comparison of eight methods. J Clin Endocrinol Metab 52:1073–1077

  10. Lecureuil M, Crouzat-Reynes G, Besnard JC, Choffel C (1978) Correlation of free thyroxine index and thyroxine: thyroxine-binding globulin ratio with the free thyroxine concentration as measured by the thyroxine and thyroxine concentration as measured by the thyroxine and thyroxine-binding globulin radioimmunoassays. Clin Chim Acta 87:373–381

  11. Refetoff S, Robin NI, Alper CA (1972) Study of four new kindreds with inherited thyroxine binding globulin abnormaltities. Possible mutation of a single gene locus. J Clin Invest 51:848–867

  12. Shishiba Y, Shimizu T, Yoshimura S, Shizume K (1970) Free thyroxine determination by equilibrium dialysis using diluted serum. Nippon Naibunpi Gakkai Zasshi 46:20–23

  13. Shishiba Y, Umezu Y (1982) Clinical evaluation of free triiodothyronine from thyrosine, thyroxine-binding globulin and triiodothyronine radio-immunoassays. Nippon Naibunpi Gakkai Zasshi 58:1139 (Abstract)

Download references

Author information

Correspondence to Yoshimasa Shishiba.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Shishiba, Y., Umezu, Y. & Ohtsuki, N. Clinical evaluation of free thyroxine calculation from thyroxine and thyroxine binding globulin radioimmunoassays. Eur J Nucl Med 8, 1–3 (1983).

Download citation


  • Public Health
  • Nuclear Medicine
  • Clinical Evaluation
  • Hypo
  • Thyroxine