A patient with viral hepatitis C who is treated with interferon alpha may develop a thyroiditis.


Mechanisms for thyroid dysfunction in these patients:

(1) autoimmune thyroiditis

(2) hepatitis C infection of follicular cells

(3) nonimmune thyroiditis secondary to a direct toxic effect


The patient may be hypothyroid, euthyroid or hyperthyroid.


The patient should be screened for thyroid disease prior to starting interferon therapy.


Risk factors for interferon-induced thyroiditis:

(1) presence of thyroid antibodies (thyroid peroxidase-Ab, thyroglobulin-Ab) prior to starting therapy

(2) female gender

(3) older age

(4) history of interferon-induced thryoiditis in the past

(5) Asian or other susceptible ethnic group


The patient should be monitored for thyroid disease during interferon therapy:

(1) weight

(2) pulse

(3) heat and cold intolerance

(4) sweating

(5) level of fatigue

(6) muscle strength

(7) TSH

(8) free T3 and free T4 if the TSH is abnormal


Signs and symptoms of thyroid dysfunction may be ascribed to the viral hepatitis, the interferon or other comorbid conditions. The diagnosis may be easily overlooked unless it is specifically looked for.


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