differentials for raised tsh and raised t4

For elevated thyroid-stimulating hormone (TSH) levels in conjunction with elevated thyroxine (T4) levels, key differential diagnoses include resistance to thyroid hormone and TSH assay interference ³. These possibilities are typically considered when a person has a persistently raised TSH despite adequate or escalating levothyroxine (LT4) treatment doses, and other underlying causes have been excluded or managed ³. An endocrinologist may arrange additional blood testing to exclude TSH assay interference or resistance to thyroid hormone ³. Other factors that can lead to persistently abnormal thyroid function tests despite LT4 treatment, potentially contributing to a complex picture, include non-compliance with prescribed LT4 treatment, drug interactions that may reduce LT4 absorption or increase LT4 requirements, and gastrointestinal conditions causing malabsorption ³.