Thyroid function in patients with proteinuria and normal or increased serum creatinine concentration.

The thyroid function of 13 patients with proteinuria and normal serum creatinine level (Group 1) and 15 patients with proteinuria and increased creatinine level (Group 2) was investigated. The daily urinary T41- and T3 excretion was much higher in Group 1 patients than in Group 2 patients (37.1 +/- 25.9 nmol T4 vs 17.5 +/- 8.7 nmol T4, 3.3 +/- 1.6 nmol T3 vs 1.1 +/- 0.8 nmol T3, respectively) and correlated in both groups with the protein loss. None of the patients suffered from hypothyroidism as a consequence of this hormone loss. Although the mean serum T4-, T3-, FT4-, FT3-, TBG- and TBPA concentrations in both groups of patients were within the normal range, the urinary hormone loss appeared to influence these values considerably. It was striking that the rT3 concentration in the patients with the highest hormone loss was frequently less than 0.08 nmol/l, the lower limit of detectability. The basal TSH levels in serum of the nephrotic patients were similar to those of normal individuals. The thyroid function of patients with proteinuria accompanied by retention of creatinine due to renal failure was more difficult to assess because different pathological mechanisms may exert their influence on the thyroidal hormone secretion as well as on the peripheral hormone metabolism.