Assessment of the thyroid function of patients undergoing regular haemodialysis.

Thyroid function has been assessed in 36 clinically euthyroid patients undergoing regular haemodialysis. The influence of erythropoietin administration on the thyroid function tests has been determined. Thyroid-stimulating hormone (TSH) has been found to be elevated in 8% of the patients. Free tri-iodothyronine was below the normal range in 67% of the population. Free tyroxine (FT4) was low in 67% of the patients when tested by an analogue method. FT4 tested by a 2-stage method in a subgroup of 22 patients was abnormally low in only 23% of the patients. Erythropoietin did not seem to improve these thyroid abnormalities despite a partial correction of the anaemia. A rise in FT4 was also observed after haemodialysis without a concomitant change in TSH concentration. This FT4 elevation was attributed to the effect of heparin.