Endocrine Abstracts

Interferon use for the treatment of chronic hepatitis infection, is associated with the side effect of thyroid dysfunction. This is frequent and can be severe, particularly if not recognised. We performed a retrospective analysis of cases of interferon related thyroid dysfunction referred to our tertiary endocrinology centre. Fourteen cases were identified over the last 8 years. An analysis was carried out of demographic features, presentation, treatment and outcomes.

The mean age was 42.5 years (range 26–52). 57% were female and 43% male. 21% were smokers and 14% had positive family history of thyroid disease. 57% of patients developed hypothyroidism, 21% developed thyroiditis, 14% hyperthyroidism and one patient developed sick euthyroidism. The mean speed of onset of thyroid dysfunction was 12.3 weeks (range 7.7–21 weeks). The most prevalent symptom in patients diagnosed with hyperthyroidism or thyroiditis was sweating (100% of patients), followed by palpitations (80%), increased stool frequency and weight loss (60%). 40% of patients were asymptomatic. Hypothyroid patients presented with weight gain (63%), fatigue (50%) and cold intolerance/poor concentration (25%). Interestingly, 86% of cases had no abnormal physical signs. There were no patients with eye signs.

TPO antibody tests were found to be positive in 36% of patients (mean 620 IU/ml). 64% of patients required treatment with levothyroxine and 29% were managed conservatively. One patient each required treatment with radioactive iodine and carbimazole.

This series demonstrates the breadth of thyroid dysfunction associated with interferon treatment. A female preponderance and a lack of thyroid eye signs was seen, as in previous studies. The mean speed of onset is 12.3 weeks which supports current recommendations to test thyroid function at the start of treatment and every three months. However, the shortest speed of onset was 7.7 weeks, suggesting that earlier testing is advisable if clinical suspicion is high.