Venlafaxine-induced Thyroiditis: A Case Report

Thyroiditis is the most common inflammatory disorder that affects thyroid gland.The diagnosis is mainly based on clinical findings, in particular the degree of pain and tenderness of thyroid. Confirmatory laboratory test includes presence of thyroid specific autoantibodies. Treatment is based on the severity of symptoms (pain and redness) and aims to restore the normal function of thyroid. Drug-induced thyroiditis has been described previously in the literature. Venlafaxine is an antidepressant agent with an efficacy similar to that of selective serotonin reuptake inhibitors. The dose of this medicine can be adjusted up to 150 mg/day one year after initiation. However, usage of venlafaxine may be limited due to the dose-dependent side effects. Here we describe a patient diagnosed with generalized anxiety disorder and migraine headache who developed venlafaxine-induced thyroiditis following dose adjustment to the maximum of 150 mg/day. The diagnosis was made based on the clinical symptoms and confirmatory laboratory tests according to the Naranjo Adverse Drug Reaction Probability Scale. Thyroiditis symptoms subsided after reducing venlafaxine dose and initiating prednisolone therapy. It should be noted that thyroid function was fully restored to normal only after cessation of venlafaxine administration.