A Study Evaluation the Safety and Efficacy of Hormone Replacement Therapy With North Star Compared to Levothyroxine in Patients With Primary Hypothyroidism

Inclusion Criteria:

• Diagnosed with primary hypothyroidism

• On continuous thyroid replacement therapy for at least 6 months before Study Entry

• On a stable daily dose of LT4 for a minimum of 12 weeks prior to Screening

• Agree to practice a method of contraception

• Female patients not pregnant or lactating at Screening

• Agree to practice a method of contraception of greater than 90% reliability

• Willing to give written informed consent for the Study

• Provide written authorization for use and disclosure of protected health information

Exclusion Criteria:

• Any clinical condition or previous surgery that might affect the absorption,distribution, biotransformation or excretion of North Star or levothyroxine

• Hospitalization for a major illness within 4 weeks prior to Screening

• Anticipated initiation or change in concomitant medications

• Concomitant use of prohibited medications or supplements

• Participated in another investigational new drug study within 30 days or 5half-lives of the IMP, whichever is longer, prior to the first study drugadministration.

• For female subjects, be pregnant, nursing or planning to become pregnant during thestudy