Total activity of peripheral deiodinases

The total activity of peripheral deiodinases ( G _D , also SPINA-GD) defines the maximum amount of triiodothyronine that can be formed from thyroxine in the entire organism under conditions of substrate saturation . It is an approximate value for the activity of 5'-deiodinases (“step-up deiodinases”) outside the CNS .

determination

In cell culture systems , the deiodination performance can be determined by measuring the T3 production or iodine release under substrate saturation with T4.

In vivo , SPINA-GD is used with

${\displaystyle {\hat {G}}_{D}={{\beta _{31}(K_{M1}+[FT_{4}])(1+K_{30}[TBG])[FT_{3}]} \over {\alpha _{31}[FT_{4}]}}}$

or

${\displaystyle {\hat {G}}_{D}={{\beta _{31}(K_{M1}+[FT_{4}])[TT_{3}]} \over {\alpha _{31}[FT_{4}]}}}$

calculated from the serum concentrations of TSH , free thyroxine and free or bound triiodothyronine .

Constant parameters of the equation are:

${\displaystyle \alpha _{31}}$: Dilution factor for T3 (reciprocal value of the apparent volume of distribution , 0.026 l ⁻¹ ) : clearance exponent for T3 (8e-6 sec ⁻¹ ) K _{M 1} : dissociation constant of type 1 deiodinase (5e-7 mol / l) K ₃₀ : Dissociation constant T3-TBG (2e9 l / mol)
${\displaystyle \beta _{31}}$

Reference ranges

Lower limit	Upper limit	Unit of measurement
20th	40	nmol / s

The equations and their parameters are calibrated for adults with a body mass of 70 kg or a plasma volume of approx. 2.5 l.

Clinical significance

In healthy people, SPINA-GD correlates with the body mass index and the TSH level. It is reduced in the case of non-thyroidal illness syndrome with hypodiodination . SPINA-GD is also reduced in certain chronic diseases such as chronic fatigue syndrome .

In men with hyperthyroidism , both SPINA-GT and SPINA-GD correlate negatively with erectile function and sexual satisfaction.

Substitution therapy with selenomethionine leads to an increase in step-up deiodination performance in people with autoimmune thyroid disease .

In a study of over 300 patients who were treated substitutively with levothyroxine , the deiodination performance also proved to be an independent predictor of the substitution dose.

See also

• Secretory capacity of the thyroid
• TSH index
• Thyroid function test

Web links

• SPINA Thyr: Open source software for calculating GT and GD
• Package " SPINA " for the statistical environment R

literature

1. ↑ Johannes W. Dietrich, Gabi Landgrafe-Mende, Evelin Wiora, Apostolos Chatzitomaris, Harald H. Klein, John EM Midgley, Rudolf Hoermann: Calculated Parameters of Thyroid Homeostasis: Emerging Tools for Differential Diagnosis and Clinical Research . In: Frontiers in Endocrinology . 7, 9 June 2016. doi : 10.3389 / fendo.2016.00057 . PMID 27375554 . PMC 4899439 (free full text).
2. ↑ ^{a b c d e} J. W. Dietrich: The pituitary-thyroid control circuit . Logos-Verlag, Berlin 2002, ISBN 3-89722-850-5 ( openlibrary.org ).
3. ↑ ^{a b} S. Liu, J. Ren, Y. Zhao, G. Han, Z. Hong, D. Yan, J. Chen, G. Gu, G. Wang, X. Wang, C. Fan, J. Li : Nonthyroidal illness syndrome: is it far away from Crohn's disease? In: J Clin Gastroenterol. tape 47 , no. 2 , 2013, p. 153-159 , doi : 10.1097 / MCG.0b013e318254ea8a , PMID 22874844 .
4. ^ JW Dietrich, G. Landgrafe, EH Fotiadou: TSH and thyrotropic agonists: key actors in thyroid homeostasis. In: Journal of Thyroid Research. Volume 2012, 2012. doi: 10.1155 / 2012/351864 . PMID 23365787 .
5. ^ R. Hoermann, JE Midgley, R. Larisch, JW Dietrich: Is pituitary TSH an adequate measure of thyroid hormone-controlled homoeostasis during thyroxine treatment? In: Eur. J. Endocrinol. Volume 168, No. 2, 2013, pp. 271-280. doi: 10.1530 / EJE-12-0819 . PMID 23184912 .
6. ^ R. Hoermann, JE Midgley, A. Giacobino, WA Eckl, HG Wahl, JW Dietrich, R. Larisch: Homeostatic Equilibria Between Free Thyroid Hormones and Pituitary Thyrotropin Are Modulated By Various Influences Including Age, Body Mass Index and Treatment. In: Clin Endocrinol (Oxf). 23 Jun 2014 doi: 10.1111 / cen.12527 . [Epub ahead of print] PMID 24953754 .
7. ↑ D. Rosolowska-Huszcz, L. Kozlowska, A. Rydzewski: Influence of low protein diet on nonthyroidal illness syndrome in chronic renal failure . In: Endocrine . tape 27 , no. 3 , August 2005, p. 283-288 , doi : 10.1385 / ENDO: 27: 3: 283 , PMID 16230785 .
8. ↑ G. Han, J. Ren, S. Liu, G. Gu, H. Ren, D. Yan, J. Chen, G. Wang, B. Zhou, X. Wu, Y. Yuan, J. Li: Nonthyroidal illness syndrome in enterocutaneous fistulas. In: The American Journal of Surgery . 206 (3), Sep 2013, pp. 386-392 doi: 10.1016 / j.amjsurg.2012.12.011 . PMID 23809674 .
9. ↑ JW Dietrich, P. Müller et al: Nonthyroidal Illness Syndrome in Cardiac Illness Involves Elevated Concentrations of 3,5-Diiodothyronine and Correlates with Atrial Remodeling . In: European Thyroid Journal . tape 4 , 2015, p. 129-137 , doi : 10.1159 / 000381543 , PMID 26279999 , PMC 4521060 (free full text) - ( karger.com ).
10. ^ S. Fan, X. Ni, J. Wang, Y. Zhang et al .: Low Triiodothyronine Syndrome in Patients With Radiation Enteritis: Risk Factors and Clinical Outcomes an Observational Study . In: Medicine . tape 95 , no. 6 , February 2016, p. e2640 , doi : 10.1097 / MD.0000000000002640 , PMID 26871787 .
11. ↑ Begoña Ruiz-Núñez, Rabab Tarasse, Emar F. Vogelaar, DA Janneke Dijck-Brouwer, Frits AJ Muskiet: Higher Prevalence of "Low T3 Syndrome" in Patients With Chronic Fatigue Syndrome: A Case-Control Study . In: Frontiers in Endocrinology . 9, March 20, 2018. doi : 10.3389 / fendo.2018.00097 .
12. ↑ R Krysiak, B Marek, B Okopień: sexual function and depressive symptoms in young men with hypothyroidism receiving levothyroxine / liothyronine combination therapy. . In: Endokrynologia Polska . 69, No. 1, 2018, pp. 16-22. doi : 10.5603 / EP.a2018.0005 . PMID 29319127 .
13. ↑ Robert Krysiak, Witold Szkróbka, Bogusław Okopień: The effect of vitamin D and selenomethionine on thyroid antibody titers, hypothalamic-pituitary-thyroid axis activity and thyroid function tests in men with Hashimoto's thyroiditis: a pilot study . In: Pharmacological Reports . 71, No. 2, October 2018, pp. 243-7. doi : 10.1016 / j.pharep.2018.10.012 . PMID 30818086 .
14. ↑ Robert Krysiak, Karolina Kowalcze, Bogusław Okopień: Selenomethionine potentiates the impact of vitamin D on thyroid autoimmunity in euthyroid women with Hashimoto's thyroiditis and low vitamin D status . In: Pharmacological Reports . 71, No. 2, December 2018, pp. 367-73. doi : 10.1016 / j.pharep.2018.12.006 . PMID 30844687 .
15. ^ JE Midgley, R. Larisch, JW Dietrich, R. Hoermann: Variation in the Biochemical Response to L-Thyroxine Therapy and Relationship with Peripheral Thyroid Hormone Conversion . In: Endocr Connect . August 2015, p. pii: EC-15-0056 , doi : 10.1530 / EC-15-0056 , PMID 26335522 .