Compared to both healthy volunteers and subjects with hypothyroidism and hyperthyroidism, SPINA-GD is reduced in subacute thyroiditis. In this condition, it has a higher specificity,  positive and negative likelihood ratio than serum concentrations of thyrotropin, free T4 or free T3. These measures of diagnostic utility are also high in nodular goitre, where SPINA-GD is elevated. Among subjects with subclinical thyrotoxicosis, calculated deiodinase activity is significantly lower in exogenous thyrotoxicosis (resulting from therapy with levothyroxine) than in true hyperthyroidism (ensuing from toxic adenoma, toxic multinodular goitre or Graves' disease). SPINA-GD may therefore be an effective biomarker for the differential diagnosis of thyrotoxicosis.
Compared to healthy subjects, SPINA-GD is significantly reduced in euthyroid sick syndrome.