[Clinical use of the assay of the thyroxin-binding-globulin (TBG) and of the calculated index: T4/TBG (author's transl)].

The level of TBG in normal adults is 2.21 +/- 0.4 mg/100 ml, without any sex difference. TBG levels are high in the neonatal period (3.26 +/- 0.49 mg/100 ml) and in children under the age of 1 year (2.61 +/- 0.66 mg). Estrogens induce a significant increase (3.96 +/- 1.0 mg) and corticoids a significant decrease of TBG (1.44 +/- 0.32 mg). TBG is also decreased in thyrotoxicosis (1.88 +/- 0.34 mg) but normal in hypothyroidism. There is a strong correlation between T4 and TBG levels, and the T4/TBG ratio appears to be a useful index, which remains constant in normal adults, and under treatment by estrogens and corticoids.