FERROUS SULFATE-INDUCED INCREASE IN REQUIREMENT FOR THYROXINE IN A PATIENT WITH PRIMARY HYPOTHYROIDISM

Recent studies have shown that under experimental conditions ferrous s ulfate may reduce the gastrointestinal absorption of orally administer ed levothyroxine sodium in patients with primary hypothyroidism. We de scribe a patient who became hypothyroid while taking ferrous sulfate. The hypothyroid status was corrected by increasing the dose of levothy roxine, Subsequently, when ferrous sulfate was discontinued, the patie nt 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 patien ts treated concurrently with ferrous sulfate and L-thyroxine.