C-reactive Protein Levels in Patients With Autoimmune Hypothyroidism Before and After Levothyroxine Treatment

Background: Hypothyroidism is one of the most common endocrine disorders. Most patients with hypothyroidism have autoimmune thyroiditis (Hashimoto's), characterized by elevated concentrations of anti-thyroperoxidase (ATPO) antibodies. Both overt hypothyroidism (OH) and subclinical hypothyroidism (SH) have been associated with cardiovascular risk factors, including markers of inflammation. High-sensitivity C-reactive protein (hs-CRP) is a veridical marker of systemic inflammation. Even a minor increase in hs-CRP is considered a cardiovascular risk; therefore, evidence of a beneficial effect of levothyroxine treatment on hs-CRP could be an argument in favor of therapy for SH.

Aim: To assess hs-CRP levels in patients with hypothyroidism and evaluate levothyroxine treatment's effect on hs-CRP.

Study design: This is a cohort study in which patients with hypothyroidism were evaluated before and after treatment with levothyroxine.

Methods: 37 patients (17 with OH and 20 with SH) and 38 healthy controls were included in the study. hs-CRP was measured at the baseline visit, then after 2 and 4 months of levothyroxine therapy at a dose necessary to achieve euthyroidism as evidenced by a normal level of thyroid-stimulating hormone (TSH).

Results: hs-CRP was significantly increased in OH (p < 0.001) and SH (p = 0.001) at baseline as compared to controls. hs-CRP significantly decreased in SH (2.2±1.6 mg/L at baseline visit, 1.4±1.1 mg/L after 2 months of levothyroxine treatment, P = 0.017) and tended to decrease in OH (2.3±1.6 mg/L at baseline visit, 1.6±1.1 mg/L after 4 months of levothyroxine treatment, P = 0.067*).

Conclusions: Patients with hypothyroidism have increased hs-CRP levels compared to a healthy control group and, thereby, a moderately increased cardiovascular risk. Achievement of euthyroidism by levothyroxine treatment decreased the levels of hs-CRP in patients with hypothyroidism.