Virus C genotype predisposes to primary hypothyroidism during interferon-α treatment for chronic hepatitis C

The treatment of the chronic hepatitis C (HCV) with α-interferon is associated with thyroid dysfunction (TD). The aim of this study was to evaluate thyroid function outcome among patients with chronic HCV under treatment with conventional interferon (IFN) or peguilated interferon (PEG-IFN) in association with ribavirin.

We studied 293 patients with chronic HCV, submitted to drug therapy for 24 or 48 weeks. Initially, we evaluated FT4, TSH, TPOAb, TgAb, and continued to monitor FT4 and TSH every three months during therapy and six months thereafter.

At baseline, TD prevalence was 6.82% (n = 20); 6.14% hypothyroidism; 0.68% hyperthyroidism. TPOAb was present in 5.46% of euthyroid patients. Out of 273 euthyroid patients at baseline, 19% developed TD: 17.2% hypothyroidism; 1.8% hyperthyroidism; 5.1% destructive thyroiditis (DT). 90% of TPOAb-positive patients at baseline developed hypothyroidism vs 14.5% of TPOAb-negative patients (p < 0.001). On average, TD occurred after 25.8 ± 15.5 weeks of treatment. 87.2% of patients who developed hypothyroidism did so during the first therapeutic cycle (p = 0.004; OR = 3.52; 95% CI = 1.36-9.65). Patients infected with genotype 1 virus were 2.13 times more likely to develop hypothyroidism (p = 0.036; 95% CI = 1.04-4.38). Hypothyroid and DT patients presented higher TSH levels before-treatment than patients who had remained euthyroid (p < 0.001; p = 0.002, respectively). DT patients presented lower qALT (p = 0.012) than euthyroid patients.

Hypothyroidism was the most frequent TD, especially during the first cycle of α-interferon. Genotype 1 virus was associated with a risk two times higher for developing the illness. There was no need to interrupt or to change HCV treatment. Therefore, approximately 34% of TD was transient.