Differential Diagnosis: Increased or Decreased Total Thyroxine
Shanna Hillsman, LVMT, University of Tennessee
M. Katherine Tolbert, DVM, PhD, DACVIM (SAIM), Texas A&M University
ArticleLast Updated September 20181 min readPeer ReviewedWeb-Exclusive
Following are differential diagnoses, listed in order of likeliness, for patients presented with increased or decreased total thyroxine (T4).
Increased Total Thyroxine
Hyperthyroidism
Functional benign adenomatous hyperplasia
Functional thyroid carcinoma
Thyroxine oversupplementation
Dietary causes
Analytical error (eg, false positive)
Decreased Total Thyroxine
Nonthyroidal illness (eg, euthyroid sick syndrome)
Hypothyroidism
Lymphocytic thyroiditis
Thyroid atrophy
Iatrogenic secondary to radioactive iodine therapy
Methimazole therapy
Thyroid neoplasia
Sulfonamides
Congenital
Hyperadrenocorticism
Drug effects
Phenobarbital
Potassium bromide
Carprofen
Clomipramine
Glucocorticoids
Propranolol
Analytical error