The reported incidence of thyroid dysfunction associated with interferon-α (IFNα) treatment for hepatitis C infection varies widely between countries.1 To our knowledge the spectrum of thyroid dysfunction in IFNα-treated Irish patients has not been described outside of an anti-D-related, hepatitis C-infected cohort.
We reviewed thyroid function tests (TFTs) from all Hepatitis C positive patients undergoing IFNα treatment over a 2 year period. 64 patients were included (41 males, 23 females). The majority of patients were Irish (48), the remainder were Eastern European (12), Italian (2), Mongolian (2).
Of 11 patients (17.2%) developed abnormal TFTs (9 female, 6 Irish). The mean age was 35 years (range 2060). The incidence of thyroid dysfunction was 12.5% for Irish patients, 33% for Eastern Europeans. Mean treatment duration at time of diagnosis of thyroid dysfunction was 18 weeks.
Transient subclinical hypothyroidism occurred in 3 patients; TSH levels ranged from 4.3 to 7.1 mIU/l (RR 0.34.0 mIU/l) and none required treatment. Two patients developed hypothyroidism requiring eltroxin, one of whom was profoundly hypothyroid (TSH 83.6 mIU/l, FT4 7.9 pmol/l, TPO Ab positive). Two developed transient hypo- and hyperthyroidism respectively, which spontaneously resolved. Two patients developed thyrotoxicosis due to destructive thyroiditis (TSH <0.1 mIU/l, FT4 1826 pmol/l, TPO Ab positive) with subsequent transient hypothyroidism, requiring temporary eltroxin treatment. The remaining two patients developed transient hyperthyroidism, later reverting to permanent hypothyroidism requiring eltroxin.
We detected clinically relevant thyroid dysfunction at a frequency similar to previous studies. Thyroid dysfunction was more common in female patients and those of Eastern European origin. All patients continued IFNα treatment and euthyroid status was achieved with medical intervention. These data suggest that frequency of TFT testing could possibly be reduced in male patients and may need to be increased in Eastern European patients. Those who develop thyroid dysfunction can be managed without discontinuation of IFNα therapy.