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Sum activity of deiodinases

The sum activity of deiodinases, abbreviated GD (for "gain of deiodinases"), also referred to as total deiodination capacity, denotes the maximum amount of T3 that is produced from T4 by periperal deiodinases in a given time unit (e.g. one second).[1]

GD can be calculated by means of a structure parameter inference approach (SPINA) from equilibrium levels of FT4 and FT3 or TT3. Calculated GD was demonstrated to correlate with body mass index[1][2][3] and thyrotropin levels,[4] and it is reduced in hypodeiodination states of nonthyroidal illness.[5][3][2]

1 Calculation

GD is obtained with

GD = beta31 (KM1 + [FT4]) (1 + K30 [TBG])[FT3]) / (alpha31 [FT4])


GD = beta31 (KM1 + [FT4]) [TT3]) / (alpha31 [FT4])

from levels of FT4 and FT3 or TT3, respectively, and, optionally, the binding protein TBG.

alpha31: Dilution factor for T3 (reciprocal of apparent volume of distribution, 0.026 l-1)
beta31: Clearance exponent for T3 (8e-6 sec-1)
KM1: Dissociation constant of type-1-deiodinase (5e-7 mol/l)
K30: Dissociation constant T3-TBG (2e9 l/mol)[1][6]

2 Reference range

Lower limit Upper limit Unit
20[1] 40[1] nmol/s

3 See also

4 Web Link

SPINA Thyr: Open source software for calculating GT and GD

5 References

  1. ISBN 9783897228504
  2. 2.0 2.1 Liu S, Ren J, Zhao Y, Han G, Hong Z, Yan D, Chen J, Gu G, Wang G, Wang X, Fan C, Li J. Nonthyroidal illness syndrome: is it far away from Crohn's disease? J Clin Gastroenterol. 2013 Feb;47(2):153-9. doi: 10.1097/MCG.0b013e318254ea8a. PMID 22874844.
  3. 3.0 3.1 Dietrich JW, Landgrafe, G, Fotiadou, EH. TSH and Thyrotropic Agonists: Key Actors in Thyroid Homeostasis Journal of Thyroid Research, vol. 2012, Article ID 351864, 29 pages, 2012. doi:10.1155/2012/351864. PMID 23365787.
  4. Hoermann R, Midgley JE, Larisch R, Dietrich JW. Is pituitary TSH an adequate measure of thyroid hormone-controlled homoeostasis during thyroxine treatment? Eur J Endocrinol. 2013;168(2):271-80. doi:10.1530/EJE-12-0819. PMID 23184912.
  5. Rosolowska-Huszcz D, Kozlowska L, Rydzewski A (2005). Influence of low protein diet on nonthyroidal illness syndrome in chronic renal failure. Endocrine. 27(3):283-8. PMID 16230785
  6. Dietrich, J. W., A. Stachon, B. Antic, H. H. Klein, and S. Hering (2008). "The AQUA-FONTIS Study: Protocol of a multidisciplinary, cross-sectional and prospective longitudinal study for developing standardized diagnostics and classification of non-thyroidal illness syndrome." BMC Endocrine Disorders 8 (13). PMID 18851740.

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