Therefore, we determined reverse T3 in subjects with low free T4 and normal or subnormal TSH levels to assess its utility in distinguishing between central hypothyroidism and euthyroid sick syndrome in adult subjects. However, the data regarding reverse T3 concentration in central hypothyroidism especially is sparse in children and none in adults. Simultaneous elevation of reverse T3 is also well documented in euthyroid sick syndrome. Low free T4 and normal or subnormal levels are also frequently encountered in outpatients during screening for thyroid dysfunction and may indicate presence of central hypothalamic or hypopituitary hypothyroidism. The patterns include low T3 and free T3 with both normal or subnormal T4 during the initial stage of an illness and variable thyroid-stimulating hormone levels ranging from subnormal to elevated depending on outcome of the illness including death or recovery respectively. Abnormal concentrations of thyroid hormone and Thyroid stimulating hormone are attributed to altered thyroid hormone metabolism in peripheral tissues as well as probable inhibition of hypothalamic-pituitary-thyroid axis. Conclusion: Reverse T3 is a reliable laboratory test differentiating between Central Hypothyroidism and “Euthyroid Sick Syndrome” in subjects with low free T4 and low/normal TSH levels.Įuthyroid sick syndrome, also known as non thyroidal illness refers to changes seen in in vitro thyroid function tests in presence of acute or chronic illness as well as during starvation and carbohydrate deprivation. On reassessment after 3 - 6 weeks, free T4, free T3, TSH and reverse T3 normalized in group with normal or elevated reverse T3 indicating recovery from “Euthyroid Sick Syndrome” whereas free T4 and reverse T3 remained subnormal in the other group suggesting presence of Central Hypothyroidism. Free T3 concentrations were subnormal or normal, 1.6 - 2.9 in individuals amongst both groups. Results: Reverse T3 established two distinct groups: 1) subnormal concentrations, 8.31 ± 0.52 2) supernormal levels 32 ± 4. Statistical analyses for comparisons were conducted between groups. Free T4, free T3, TSH and reverse T3 levels were also determined in age-matched 35 healthy volunteers and reassessed in study group. Subjects and Methods: Free T3 and Reverse T3 were determined as “add on” tests using previously drawn blood samples of 78 consecutive adults showing low free T4, 0.80 ± 0.02 and low/normal TSH, 1.29 ± 0.40. Objective: Evaluation of reverse T3 to differentiate between “Euthyroid Sick Syndrome” and Central Hypothyroidism. Repeated determination of these tests may help differentiate between these disorders. However, accurate diagnosis is difficult even with determination of free T3 being low/normal in both. Background: Low free T4 and normal/low TSH concentrations are often noted in clinical practice and denote presence of “Euthyroid Sick Syndrome” or Central Hypothyroidism.
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