A Hidden Link between Subclinical Hypothyroidism and Depression: A literature Review

Abstract

The association between Subclinical hypothyroidism and Depression is recognised. It is found that patients with Thyroid disorders are more prone to develop depressive symptoms and depression may be accompanied by various subtle thyroid abnormalities. The most commonly documented abnormalities are elevated T4 levels, Low T3, elevated rT3, a blunted TSH response to TSH, Positive anti thyroid autoantibodies and elevated CSF TRH concentrations. It is also found that thyroid hormone supplements appear to accelerate and enhance the clinical response to antidepressants. It is found out that Depression is associated with changes in Hypothalamic-pituitary axis as thyroid hormones act on the central nervous system. Mild thyroid dysfunction causes depression in younger patients (<60 years old) diagnosed by depressive scale. It was found that differences in age group may cause depressive episodes. Depressive episodes such as anxiety and the risk of committing suicide are considerable factors that differ according to the age of the individuals.SCH was found to be associated with depression in the younger adults (<60 years old). The only difference between SCH and normal thyroid function is TSH.In depressive disorder and subclinical hypothyroidism sex differences have also been recognised. Association between subclinical hypothyroidism and Depression is assessed by various depressive scores such as Beck Depression Inventory and Hamilton depression rating scale. As Subclinical hypothyroidism is associated with low mood, Serum levels of TSH, FT3, FT4 and Hamilton depression, treatment with Levothyroxine showed significant decrease is TSH levels and Hamilton scores were decreased. Since the prevalence of depressive symptoms in hypothyroidism is high TSH cut-off levels is used,TSH cut off value for hypothyroidism is based on associated symptoms,TSH cut-off value is 2.5 MIU/L is optimal.