Changes In Free T4 Research Articles

Evaluation of Thyroid Function in Patients Treated with Continuous Ambulatory Peritoneal Dialysis (CAPD)

Abnormal thyroid function has been described in chronic renal insufficiency, and further changes occur with increasing time on hemodialysis. This study on two groups of patients was done to determine whether treatment with CAPD induces changes in thyroid function. Group A included 16 patients with an average duration of treatment of 2.1 ± 1.1 months; group B included 12 patients with 8.1 ± 2 months. We measured total T4 and T3, free T4, TBG, RT3U, FTI, T4/T3 and basal TSH, and TSH induced by TRH stimulation in plasma, and total and free T4 in dialysate. The results showed a significant decrease in total T4 and T3 in plasma, but no change in free T4 or TSH and no appreciable amounts of the hormones in the dialysate. We believe the decrease in total T4 and T3 is secondary to alterations in transport proteins while thyroid function is maintained by normal free T4 and TSH levels more dependable parameters for the interpretation of thyroid function in chronic diseases.

A comparison of free T4 and the ratio of total T4 to T4-binding globulin in serum through pregnancy.

Serum free T4 concentrations have been variously reported as either constant or falling in pregnancy. In this study, 122 serum samples from apparently normal pregnancies were used to derive euthyroid ranges throughout pregnancy for T4 and free T4 (measured by the Amerlex kits) and for T4-binding globulin (TBG). The mean free T4 concentration fell with increasing gestational age, the range of values in the third trimester being narrower than the non-pregnant normal range. Evidence is reviewed which shows that the Amerlex free T4 assay is unaffected by the elevation of TBG in non-pregnant subjects. The decline in mean free T4 as pregnancy proceeds is in good agreement with the change in free T4 predicted by the falling T4/TBG ratio.