Abstract
To the Editor:
We are very thankful to Drs. McCowen and Garber for their enlightening considerations in response to our study (1). Our study evaluated the effects of the selective serotonin reuptake inhibitor (SSRI) antidepressants fluoxetine and sertraline on thyroid indices of patients with major depression and clinical hypothyroidism and compared these results with a control group with major depression and normal thyroid function. During the 3-month period of evaluation, hypothyroid patients were maintained on their usual levothyroxine dose. Neither patients who were taking sertraline nor those taking fluoxetine required a change in their levothyroxine dose after either of the SSRIs was introduced. Thyroid function tests were unaffected by these SSRIs not only in thyroxine-replaced hypothyroid patients but also in those with normal thyroid function. It is possible that a long-term observation period might have demonstrated slightly different results.
We agree with Dr. McCowen and Dr. Garber that there is great heterogeneity in patients with hypothyroidism. The majority of our patients were not athyreotic, because in most the cause of hypothyroidism was autoimmune thyroiditis. This is the case for the majority of hypothyroid patients encountered in day-to-day clinical practice. There are many individual aspects to be considered when SSRI therapy is started. Careful clinical follow-up is mandatory as individual responses cannot always be predicted.