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Table 2 Decision criteria

From: 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

Criterion Definition
Thyrotropic insufficiency a) Reduced levels of both TSH and free T4.
b) Thyrotroph T4 Sensitivity Index (TTSI) reduced below its reference interval.
Reduced plasma protein binding a) Reduced relative ratios of bound and free hormone levels
b) Reduced apparent dissociation constant of T3 at thyroxin binding globulin (K30)
Reduced deiodation a) Reduced level for free T3
b) diminished T3/T4-ratio
c) reduced sum activity of peripheral 5'-Dejodinase (GD^)