What is the role of psychiatric illness in the development of euthyroid sick syndrome?

Updated: Aug 28, 2020
  • Author: Serhat Aytug, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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The alterations in thyroid function test results are varied and confusing. The factors that cause alterations in thyroid function test results, such as the specific psychiatric illness, age of the patient, stage of the patient's illness, concomitant medications, and the presence of other thyroidal illnesses and NTIs, are variable. In primary depression, total T4 can be elevated or unchanged, free T4 can be elevated or unchanged, total T3 is unchanged, free T3 is unchanged, rT3 is elevated, basal TSH is unchanged, and TSH response to TRH is decreased. One of the most common abnormality in thyroid function test findings in acute psychiatric admissions is an elevation of FTI (7-9% of patients). This is secondary to a transient increase in T4, which is rare in other diseases. Elevated total T4 and FTI normalize after treatment.

The TRH response is blunted in depression but not in schizophrenia. In a 2006 study, out of 250 subjects with major psychiatric depression, 6.4% exhibited low T3 syndrome and these were not ascribed to malnutrition or any other illness and the metabolic parameters were all normal. [28]

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