Clinical Aspects of Thyrotropin Circadian Variability
We retrospectively analyzed the results of measurements of serum TSH concentrations perfomed in 14760 outpatients since October 2008 till October 2009 (n = 14760) in Federal Endocrinological Research Center. Data have been parted on two groups. Results of measurements of serum TSH concentrations between 8.00 and 11.00 h have been included in the first group (n = 14397), between 15.00 and 17.00 h – in the second group (n = 363). The median of TSH concentrations of the first group was 1,58 mU/l, the second group – 1,1 mU/l (р <0,05). According to the present TSH reference ranges (0,4–4,0 mU/l), prevalence of a hypothyroidism in the first group was 13%, in the second group was 6% (р <0.0001). Also smaller prevalence of TSH 2,5–4,0 mU/l has been defined in the second group (р <0,0001). Prevalence of TSH 0,4–2,5 mU/l has been calculated as 60% in the first group and as 69% – in the second. Тhus thyrotropin circadian variability are necessary for considering at discussion of changes in TSH reference range.