New insights into thyroid hormone replacement therapy

It is widely accepted that thyroid hormone replacement for patients with hypothyroidism can be fully accomplished with levothyroxine monotherapy, as assessed by serum thyroid function tests. However, approximately 10% of hypothyroid patients are dissatisfied with the outcome of levothyroxine monotherapy, and physicians continue to report benefits from combined levothyroxine-triidothyronine therapy for some hypothyroid patients. Recently, a large prospective study reported that the benefit of the combined levothyroxine-triidothyronine therapy is associated with the Thr92Ala polymorphism in the type 2 deiodinase gene, which is present in about 15% of the general population. If confirmed, these findings indicate that personalized medicine is rapidly catching up with modern thyroidology.