Table 4 Potential causes of thyrotropin elevation in patients (thyroxine treated) with primary hypothyroidism

Suboptimal dosing, inadequate prescribed dosage, dispensing error

Non compliance

Progressive decrease in endogenous thyroxine production

Drug and supplement interactions

Co-morbidities

Malabsorption disorders

Autoimmune thyroiditis

Previous thyroid irradiation

Reduced thyroxine absorption

Other systemic illnesses