Secretory capacity of the thyroid

The secretion capacity of the thyroid gland ( G _T , also known as incretion capacity or, if calculated from hormone levels, referred to as SPINA-GT) defines the maximum stimulated amount of thyroxine that the thyroid can release into the bloodstream in one second .

detection

The secretion performance can be determined experimentally by measuring the T4 production of the thyroid gland after stimulation with a high TSH concentration (for example in the form of rhTSH , ie recombinant human TSH). In the past, secretion performance was also estimated by measuring the serum concentration of the protein-bound iodine isotope ¹³¹ I after administration of radioiodine . Due to the associated high radiation exposure , this procedure is no longer used in routine examinations.

In vivo , SPINA-GT can also with

${\displaystyle {\hat {G}}_{T}={{\beta _{T}(D_{T}+[TSH])(1+K_{41}[TBG]+K_{42}[TBPA])[FT_{4}]} \over {\alpha _{T}[TSH]}}}$

or

${\displaystyle {\hat {G}}_{T}={{\beta _{T}(D_{T}+[TSH])[TT_{4}]} \over {\alpha _{T}[TSH]}}}$

can be calculated from serum levels of TSH and free or total thyroxine . This physiologically based equation is the most widely used standard method for determining the secretion capacity of the thyroid gland today.

Constant parameters of the equations are:

${\displaystyle \alpha _{T}}$: Dilution factor for T4 (reciprocal of the apparent volume of distribution , 0.1 l ⁻¹ ) : clearance exponent for T4 (1.1e-6 sec ⁻¹ ) K ₄₁ : dissociation constant T4- TBG (2e10 l / mol) K ₄₂ : dissociation constant T4 - TBPA (2e8 l / mol) D _T : EC ₅₀ for TSH (2.75 mU / l)
${\displaystyle \beta _{T}}$

The quotient of SPINA-GT and thyroid volume determined sonographically is called the specific secretion capacity (SPINA-GTs).

Reference ranges

Lower limit	Upper limit	Unit of measurement
1.41	8.67	pmol / 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

SPINA-GT is increased in the case of primary hyperthyroidism and reduced in the case of primary hypothyroidism . The secretion performance correlates with the sonographically determined thyroid volume and showed in a longitudinal study a higher reliability than TSH , FT4 or FT3 . A negative correlation between GT and creatinine clearance was observed in one study . In the initial phase of a non-thyroidal illness syndrome , SPINA-GT passager can be slightly elevated. On the other hand, SPINA-GT may be reduced in certain chronic diseases such as chronic fatigue syndrome .

In men with hypothyroidism , both SPINA-GT and SPINA-GD correlate negatively with erectile function and sexual satisfaction. In women with thyrotoxicosis , increased secretion rates predict sexual dysfunction and a higher degree of depression .

In people with autoimmune thyroid disease and a borderline low vitamin D supply, the secretion performance increases under therapy with 25-hydroxycholecalciferol . Therapy with selenomethionine seems to increase this effect. An adequate supply of vitamin D is also necessary for the effect that statins have on secretion performance.

The specific secretion capacity (SPINA-GTs) is increased in obesity and autoimmune thyroiditis .

See also

• Total activity of peripheral deiodinases
• 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. ↑ ^{a b c d e f g} Dietrich, JW: The pituitary-thyroid control circuit . Logos-Verlag Berlin, Berlin 2002, ISBN 978-3-89722-850-4 .
2. ↑ 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).
3. ↑ JR Bierich: Endocrinology. In: H. Wiesener: Introduction to the developmental physiology of the child . Springer, [Sl] 1964, ISBN 978-3-642-86507-7 , p. 310.
4. ↑ Dietrich JW, Stachon A, Antic B, Klein HH, Hering S: 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 . In: BMC Endocr Disord . 8, No. 1, Oct 2008, p. 13. doi : 10.1186 / 1472-6823-8-13 . PMID 18851740 . PMC 2576461 (free full text).
5. ↑ ^{a b} 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 .
6. ↑ Dietrich, J., M. Fischer, J. Jauch, E. Pantke, R. Gärtner and CR Pickardt (1999). "SPINA-THYR: A Novel Systems Theoretic Approach to Determine the Secretion Capacity of the Thyroid Gland." European Journal of Internal Medicine 10, Suppl. 1 (5/1999): S34.
7. ↑ Dietrich JW. Thyrotoxic crisis. Med Klin Intensivmed Notfmed. 2012 Sep; 107 (6): 448-53. Epub 2012 Aug 11. German. PMID 22878518
8. ^ X Wang, H Liu, J Chen, Y Huang, L Li, S Rampersad, S Qu: Metabolic Characteristics in Obese Patients Complicated by Mild Thyroid Hormone Deficiency. . In: Hormone and Metabolic Research . April 21, 2016. PMID 27101096 .
9. ↑ 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 .
10. ↑ Rosolowska-Huszcz D, Kozlowska L, Rydzewski A. Influence of low protein diet on nonthyroidal illness syndrome in chronic renal failure. Endocrine. 2005 Aug; 27 (3): 283-8. PMID 16230785 .
11. ↑ 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? . In: J Clin Gastroenterol. . 47, No. 2, 2013, pp. 153-9. doi : 10.1097 / MCG.0b013e318254ea8a . PMID 22874844 .
12. ↑ 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 .
13. ↑ R Krysiak, K Kowalcze, B Okopień: sexual function and depressive symptoms in young women with overt hyperthyroidism. . In: European journal of obstetrics, gynecology, and reproductive biology . 234, January 9, 2019, pp. 43-48. doi : 10.1016 / j.ejogrb.2018.12.035 . PMID 30654201 .
14. ↑ ^{a b} 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 .
15. ↑ ^{a b} 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 .
16. ↑ R Krysiak, W Szkróbka, B Okopień: The Relationship Between Statin Action On Thyroid Autoimmunity And Vitamin D Status: A Pilot Study. . In: Experimental and clinical endocrinology & diabetes: official journal, German Society of Endocrinology [and] German Diabetes Association . 127, No. 1, August 27, 2018, pp. 23-28. doi : 10.1055 / a-0669-9309 . PMID 30149415 .
17. ^ Rudolf Hoermann, John EM Midgley, Rolf Larisch, Johannes W. Dietrich: Relational Stability of Thyroid Hormones in Euthyroid Subjects and Patients with Autoimmune Thyroid Disease . In: European Thyroid Journal . August 18, 2016. doi : 10.1159 / 000447967 . PMID 27843807 .