Desiccated Thyroid Extract Versus Synthetic T3/T4 Combination (ThyrolarTM) Versus L-T4 Alone in the Therapy of Primary Hypothyroidism With Special Attention to the Gene Polymorphism

The proposed study design is a prospective, randomized, double-blind, crossover study. After informed consent is obtained, patients will be randomized to receive either desiccated thyroid in capsules, or L-T4/L-T3 (ThyrolarTM) in capsules, or L-T4 alone capsules. All study participants, physician investigators, those administering the neurocognitive tests and those analyzing test results will be blinded throughout the study.

Subjects will undergo memory testing, a disease specific symptom questionnaire, a general mental health assessment, a complete physical examination, baseline EKG, and biochemical testing consisting of serum TSH, free T4, total T4, total T3, free T3, T3 resin uptake, reverse T3, sex hormone binding globulin (SHBG), serum iodine, a lipid panel, insulin, glucose and leptin. This testing and DXA scan of body composition will be performed at baseline and after each 3 month treatment period. Deiodinase type 2 (DIO2) polymorphisms analyses - will also be performed at the beginning of the study and the results will be blinded to the investigators performing the memory testing.

After 5-6 weeks on the study medication, TSH levels will be checked and the medication adjusted to maintain TSH level between 0.46-4.68 mIU/L. Once the TSH level is in the desired range, subjects will continue the medication for an additional 6 weeks. Subjects will then be crossed-over to the other treatment arm for 3 months. Again, testing will be performed after each treatment period. Finally the subjects will again switched over to the 3rd arm and testing will be performed after treatment period.

A cross-over design is preferred because we are assessing subjective symptoms such as clinical well-being and other parameters. Therefore, we will be able to evaluate the effectiveness of L-T4/T3 (ThyrolarTM) vs DTE vs T4 alone in the same patientssubjects. This is also supported by the previous study by Escobar-Morreale et al.

Additionally, the Wechsler memory scale, DEXA for body composition, measurment of reverse T3, insulin, leptin, and DIO2 polymorphisms analysis will be included for the research portion of this study. Further, the frequency of serum blood draws, for research purposes, will be at intervals of 0, 6, 12, 18, 24, 30 and 36 weeks.