title: Ferrous sulfate-induced increase in requirement for thyroxine in a patient with primary hypothyroidism.
abstract: Recent studies have shown that under experimental conditions ferrous sulfate may reduce the gastrointestinal absorption of orally administered levothyroxine sodium in patients with primary hypothyroidism. We describe a patient who became hypothyroid while taking ferrous sulfate. The hypothyroid status was corrected by increasing the dose of levothyroxine. Subsequently, when ferrous sulfate was discontinued, the patient became hyperthyroid while taking the higher dose of thyroid hormone preparation. Since both hypothyroidism and iron deficiency anemia may coexist, additional thyroid function testing is recommended in patients treated concurrently with ferrous sulfate and L-thyroxine.
authors.affiliation: Department of Internal Medicine, National Naval Medical Center, Bethesda, MD 20889-5600, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Shakir
authors.forename: J P
authors.initials: JP
authors.lastname: Chute
authors.forename: B S
authors.initials: BS
authors.lastname: Aprill
authors.forename: A A
authors.initials: AA
authors.lastname: Lazarus
mesh_terms: D000284:Administration, Oral; D000328:Adult; D018798:Anemia, Iron-Deficiency / Q000188:drug therapy; D004347:Drug Interactions; D005260:Female; D005296:Ferrous Compounds / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D006801:Humans; D006980:Hyperthyroidism / Q000139:chemically induced; D007037:Hypothyroidism / Q000188:drug therapy*; D007408:Intestinal Absorption / Q000187:drug effects; D013967:Thyroiditis, Autoimmune / Q000150:complications; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*
chemical_list: D005296:Ferrous Compounds; C020748:ferrous sulfate; D013972:Thyrotropin; D013974:Thyroxine