GD

Definition

G_D, also referred to as SPINA-GD, is an abbreviation for "gain of deiodinases". It is a mathematical symbol for calculated sum activity of peripheral 5' deionidases type 1 (DIO1) and type 2 (DIO2). Calculation of G_D is part of a structure-parameter inference approach, a method that is used e.g. in experimental thyroid research. The equations are derived from a mathematical model of thyrotropic feedback control.

Calculation

$\hat G_D = {{\beta _{31} (K_{M1} + [FT_4 ])(1 + K_{30} [TBG])[FT_3 ]} \over {\alpha _{31} [FT_4 ]}}$

$\hat G_D = {{\beta _{31} (K_{M1} + [FT_4 ])[TT_3 ]} \over {\alpha _{31} [FT_4 ]}}$

$\alpha _{31}$: Dilution factor for T3 (reciprocal of apparent volume of distribution, 0.026 l^-1)
$\beta _{31}$: Clearance exponent for T3 (8e-6 sec^-1)
K_M1: Dissociation constant of type-1-deiodinase (5e-7 mol/l)
K₃₀: Dissociation constant T3-TBG (2e9 l/mol)

Reference range

20 - 40 nmol/sec (in adult humans)

see also: G_T, SPINA

Web Links

• SPINA Reference
• SPINA-Thyr (Software for calculating GD)

References

1. Dietrich, J., M. Fischer, J. Jauch, E. Pantke, R. Gärtner und C. R. 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.
2. Dietrich, J. W. (2002). Der Hypophysen-Schilddrüsen-Regelkreis. Entwicklung und klinische Anwendung eines nichtlinearen Modells. Berlin, Logos-Verlag.
3. 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
4. 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.