TABLE 6-1 Protocol for Controlled Clinical Study

General Aspects

  • Design: Double blind

  • Number of subjects: 90 healthy adults (45 men and 45 women)

Selection of Subjects

  • Only subjects with normal examination and laboratory results should be includeda

  • Subjects with 24-hr urinary iodide excretion over 500 µg to be excluded

  • Only nonpregnant women (confirmed by pregnancy testing before study) should be included; effective contraception must be used during study period

  • Subjects with high serum antithyroid antibody titers should not be excluded

Treatment Groups

  • Subjects randomly assigned to receive 1 of 2 potassium perchlorate doses or placebo for 6 months

  • Group size: placebo (15 men and 15 women), 0.04 mg/kg per day (15 men and 15 women), and 0.1 mg/kg per day (15 men and 15 women); these doses are predicted to reduce short-term 24-hr thyroid iodide uptake by about 25% and 45%, respectively

  • Potassium perchlorate and placebo administered in drinking water

Clinical Testing

  • Physical examination and measurements of serum free T4, T3, TSH, antithyroid peroxidase antibodies, and thyroglobulin; thyroid ultrasound at baseline, 1 week, 2 weeks, monthly

  • 24-hr urine collection for iodide at baseline, and 1, 3, and 6 months

  • 24-hr urinary and serum perchlorate at baseline, monthly to ensure compliance

  • 24-hr thyroid 123I uptake at baseline, 2 weeks, 3 months, 6 months

  • Serum free T4, T3, TSH, antithyroid antibodies, and thyroglobulin; thyroid ultrasound; urinary iodide; urinary and serum perchlorate 1 month after perchlorate discontinuation

  • Ultrasound studies done without examiner knowledge of treatment group

Safety Monitoring

  • Data safety monitoring board should monitor thyroid function and ultrasound data

  • Subjects should be withdrawn from study if serum TSH rises to over 10 mU/L or thyroid volume increases by 100% over baseline at any time

aDecision is based on physical examination before study with evaluation of complete blood cell count, routine chemistries, thyroid function, antithyroid peroxidase antibody titers, and pregnancy status.

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