Variations in the DIO2 and MCT10 Genes and Effect of Triiodothyronine Treatment

Longtime Effect of Combination Treatment With L-thyroxine (L-T4) and Liothyronine (L-T3) in Patients With Persistent Hypothyroid Symptoms - Relation to Polymorphisms (SNP) in the DIO2 and the MCT10 Gene

Hypothesis: Variations in the deiodinase 2 gene and monocarboxylate transporter 10 gene is associated with improvement in quality of life after initiation of combination therapy with L-Thyroxine and Liothyronine in patients with persistent hypothyroid symptoms despite conventional L-thyroxine mono-therapy.

Purpose: To re-test this hypothesis in patients with continued perceived effect of Liothyronine treatment at least one year after initiation in a patient population more representing of daily clinical practice. The study will help determine whether testing of specific gene variations might predict longtime effect of combination therapy.

Inclusion Criteria:

• Patients admitted to the department of endocrinology with the diagnose hypothyroidism because of persistent hypothyroid symptoms despite treatment with L-thyroxine mono-therapy and normal and stable TSH (for at least 6 months).
• Started in combination therapy with L-thyroxine and Liothyronine in an approximately 17/1 ratio
• Exclusion of an alternative explanation for persistent hypothyroid symptoms

Exclusion Criteria:

• Initiation of L-thyroxine treatment in patients with s-TSH below upper normal limit (with assay in current use, that is TSH < 4 mU/L)
• Ongoing pregnancy
• Age below 18 years or above 80 years.
• Patients who do not read and understand information material given
• Patients who are not competent to give informed consent