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## DefinitionEdit

GD, 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 GD 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.

## CalculationEdit

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

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

$\alpha _{31}$: Dilution factor for T3 (reciprocal of apparent volume of distribution, 0.026 l-1)
$\beta _{31}$: Clearance exponent for T3 (8e-6 sec-1)
KM1: Dissociation constant of type-1-deiodinase (5e-7 mol/l)
K30: Dissociation constant T3-TBG (2e9 l/mol)

## Reference range Edit

20 - 40 nmol/sec (in adult humans)