Low-grade systemic inflammation in subclinical hypothyroidism

Abstract

Background: Hypothyroidism is the deficiency in the production of thyroid hormones to meet the requirements of peripheral tissues. Subclinical hypothyroidism (SCH) is defined biochemically as normal serum free thyroxin concentration in the presence of an elevated serum thyroid-stimulating hormone (TSH) concentration. SCH may be associated with low-grade systemic inflammation (increased high sensitivity-C reactive protein (hs-CRP), one possible explanation may be that TSH in adipocytes promotes the release of interleukin-6 (IL-6). Studies have confirmed inflammatory biomarkers like hs-CRP and IL-6 to be a predictor of cardiovascular (CV) events. However, the treatment of SCH remains subject to debate. Conclusions: It is increasingly evident that SCH has prognostic values and crucial clinical effects, which leads to the view of SCH not being a compensated biochemical change sensu strictu. Even a modest but consistent fluctuation in the circulating thyroid hormone levels can create a response from the human heart. Well-timed treatment should be considered as a precaution to avoid the unfavourable CV diseases. The inflammatory biomarkers, namely CRP and IL-6 are exceptionally robust markers of cardiovascular risk. Thus, using these biomarkers may be helpful in assessing the cardiovascular risk in patients with subclinical hypothyroidism.

Keywords

• subclinical hypothyroidism
• low-grade inflammation
• levothyroxine treatment