DRUG-INDUCED THYROID-DISORDERS

Many drugs can interfere with biochemical tests of thyroid function by interfering with the synthesis, transport and metabolism of thyroid h ormones, or by altering the synthesis and secretion of thyrotrophin (t hyroid-stimulating hormone; TSH). Only rarely, however, do these effec ts cause overt, clinically apparent thyroid disease. Lithium therapy c auses overt hypothyroidism in 5 to 15% of patients, and goitre in up t o 37%. Thyroid function tests should be performed prior to initiating lithium therapy, and at 6-monthly intervals thereafter. Iodine and iod ine-containing drugs (e.g radiographic contrast media, iodinated glyce rol and amiodarone) can have profound and variable effects on thyroid function.