Abstract
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. However, accurate diagnosis is difficult even with determination of free T3 being low/normal in both. Repeated determination of these tests may help differentiate between these disorders. Objective: Evaluation of reverse T3 to differentiate between “Euthyroid Sick Syndrome” and Central Hypothyroidism. 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 [normal ranges, 0.89 - 1.70 mcg/dl; 0.45 - 4.67 uU/ml]. Free T4, free T3, TSH and reverse T3 levels were also determined in age-matched 35 healthy volunteers and reassessed in study group. Statistical analyses for comparisons were conducted between groups. All data are reported as Mean ± SEM. Results: Reverse T3 established two distinct groups: 1) subnormal concentrations, 8.31 ± 0.52 [range, 11 - 14 ng/dl]; 2) supernormal levels; 32 ± 4 [normal Range 12 - 26]. Free T3 concentrations were subnormal or normal, 1.6 - 2.9 [normal range, 2.3 - 4.2 ng/ml] in individuals amongst both groups. 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. 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.
Highlights
Euthyroid sick syndrome, 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 [1]-[15]
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
On reassessment after 3 - 6 weeks, free T4, free T3, TSH and reverse T3 levels normalized in the group with elevated reverse T3 indicative of recovery from “Euthyroid Sick Syndrome”
Summary
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 [1]-[15]. 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. Low free T4 and normal/low TSH concentrations are often noted in clinical practice and denote presence of “Euthyroid Sick Syndrome” or Central Hypothyroidism. 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. 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
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.