Genetic Variants in Thyroid Hormone Pathway Genes
Genetic variants in thyroid hormone pathway genes (ie, deiodinases or thyroid hormone transporters) are linked to small changes in serum thyroid levels; however, the clinical relevance of these effects remain unknown in patients taking thyroid replacement therapy. While data do suggest that polymorphisms of the type 2 deiodinase gene may be associated with successful response to combination therapy with synthetic triiodothyronine and levothyroxine therapy, controlled studies are needed for confirm these findings. Thus, the ATA does not recommend genetic testing to guide treatment decisions regarding combination therapy.
Synthetic Combination Therapy
The ATA recommends against the routine use of combination therapy with levothyroxine plus liothyronine in patients with primary hypothyroidism due to conflicting findings in the literature and lack of long-term outcomes. This combination therapy also is not recommended for routine use in patients with residual symptoms during treatment with levothyroxine monotherapy, again because of a lack of long-term studies.
While short-term studies suggest that synthetic liothyronine may have beneficial effects on weight, lipid levels, and depression in hypothyroid patients, long-term controlled clinical trials using a longer acting form of triiodothyronine are needed before this treatment can be recommended for routine clinical use. The ATA does not recommend liothyronine as monotherapy for treatment of hypothyroidism. In addition, the ATA recommends against use of this agent for treating obesity in euthyroid patients.
The ATA recommends against the routine use of compounded thyroid hormones due to safety and potency concerns as well as lack of conclusive data suggesting that compounded thyroid hormones are superior to standard preparations. The ATA states that compounded products may be considered in certain circumstances, such as in patients with suspected allergy to a component of standard preparations.
Dietary Supplements and Over-the-Counter Products
The ATA recommends against use of dietary supplements, neutraceuticals, or over-the-counter products in the treatment of hypothyroidism or for people who are euthyroid. The ATA warns specifically that pharmacologic doses of iodine may cause thyrotoxicosis or hypothyroidism in patients with underlying thyroid pathology.
Wilson’s Temperature Syndrome is the presence of clinical symptoms of hypothyroidism accompanied by a normal thyroid-stimulating hormone (TSH) level. However, the ATA notes a lack of scientific evidence to support the diagnosis of Wilson’s Syndrome or Wilson’s Temperature Syndrome and, thus, recommends against the use of triiodothyronine escalation therapy for this syndrome.
March 12, 2015
American Thyroid Association Hypothyroidism Guideline Summary Continues at:
Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the Treatment of Hypothyroidism. Thyroid. 2014 Sep 29. [Epub ahead of print] http://online.liebertpub.com/doi/abs/10.1089/thy.2014.0028. Accessed March 12, 2015.