[Thyroid hormone level in the serum in untreated hypothyroidism and in substitution therapy]

Forty-seven patients with clinically revealed hypothyrosis were examined. Of these, 31 subjects were untreated and 16 were in a compensatory stage of the disease after the substitution treatment. All the untreated patients had lowered serum concentration of total thyroxin (TT4) and free thyroxin (FT4I) indices, their mean arithmetical values being statistically different in the mild and moderate stages of the disease. The total triiodothyronine (T3) level was within normal in 10 of 31 patients. The reverse T3 concentration was normal in patients with the mild stage of the disease and three times lower in the moderate form. T3 concentration was moderately increased in 7 treated patients, whereas 2 of them had TT4 and FT4I indices below normal. T4 deficiency is likely to be the crucial factor in the clinical manifestations of all hypothyrosis forms. Dissimilar changes in the total and reverse T3 levels in some patients are seemed to be caused by the compensatory mechanism and cannot serve as the main diagnostic criterion.