Each subject will have blood samples taken to determine the pharmacokinetics of serum TSH at -12 hours and just prior to dosing and at various hours up to 14 days following the administration of Thyrogen or the modified release formulation. In addition, for the evaluation of pharmacodynamics, each subject will have samples of blood taken to determine serum free T4, total T4, free T3, and total T3 at -12 hours and just prior to dosing and at various hours up to 14 days following the administration of study treatments.