Serum T3 and reverse T3 concentrations: indices of metabolic control in diabetes mellitus.

Several previous studies have reported that serum T3 and reverse T3 (rT3) concentrations are altered in uncontrolled diabetes mellitus and their normalization occurs when euglycemia is achieved. Therefore, this study was undertaken to examine the usefulness of serum T3 and rT3 levels as indices of metabolic control in diabetes mellitus. Serum T3, rT3, T4, Free T4, TSH and T3 resin uptake were determined in 18 normal subjects and 35 patients with newly discovered diabetes mellitus before initiation of therapy and reassessed after normalization of glycosylated hemoglobin (HbA1) concentration. These thyroid hormone concentrations were compared to the well established parameters of metabolic control such as fasting plasma glucose (FPG), peak plasma glucose (PPG), area under the curve of the oral glucose tolerance test (sigma G), 24 hr urinary glucose level (UG), HbA1 as well as glycosylated protein (GlyPr) and glycosylated albumin (GlyAlb) concentrations. Serum T4, T3RU, Free T4 and TSH concentrations in patients with diabetes mellitus prior to treatment were not significantly different from normal subjects and were not significantly correlated with any of the parameters of diabetic control. Serum T3 was significantly lower and serum rT3, significantly higher in diabetic patients prior to treatment as compared to normal subjects and both T3 and rT3 normalized in 20 patients studied when adequate metabolic control was achieved as reflected by normalization of HbA1 (less than 8.2%). Furthermore, significant negative and positive correlations were noted between parameters of metabolic control and serum T3 and rT3 levels respectively. Therefore, this study demonstrates that serum T3 and rT3 may be reliable indices of metabolic control in diabetes mellitus.(ABSTRACT TRUNCATED AT 250 WORDS)