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Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism.
Ann Intern Med. 1992 Dec 15; 117(12):1010-3.AIM

Abstract

OBJECTIVE

To determine whether simultaneous ingestion of ferrous sulfate and thyroxine reduces the efficacy of thyroid hormone in patients with primary hypothyroidism.

DESIGN

Uncontrolled clinical trial.

SETTING

Outpatient research clinic of a tertiary care center.

PATIENTS

Fourteen patients with established primary hypothyroidism on stable thyroxine replacement.

INTERVENTION

All patients were instructed to ingest simultaneously, a 300-mg ferrous sulfate tablet and their usual thyroxine dose every day for 12 weeks.

RESULTS

After 12 weeks of ferrous sulfate ingestion with thyroxine, the mean level of serum thyrotropin (thyroid stimulating hormone, TSH) rose from 1.6 +/- 0.4 to 5.4 +/- 2.8 mU/L (P < 0.01), but the free thyroxine index did not change significantly. Subjective evaluation using a clinical score showed that nine patients had an increase in symptoms and signs of hypothyroidism; the mean score for the 14 patients changed from 0 to 1.3 +/- 0.4 (P = 0.011). When iron and thyroxine were mixed together in vitro, a poorly soluble purple complex appeared that indicated the binding of iron to thyroxine.

CONCLUSIONS

Simultaneous ingestion of ferrous sulfate and thyroxine causes a variable reduction in thyroxine efficacy that is clinically significant in some patients. The interaction is probably caused by the binding of iron to thyroxine.

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Authors+Show Affiliations

Campbell NR
Department of Medicine, Faculty of Medicine, University of Calgary, Alberta, Canada.
Hasinoff BB
No affiliation info available
Stalts H
No affiliation info available
Rao B
No affiliation info available
Wong NC
No affiliation info available

MeSH

AdultAgedFemaleFerrous CompoundsHumansHypothyroidismMaleMiddle AgedPatient ComplianceSpectrophotometryThyrotropinThyroxine

Pub Type(s)

Clinical Trial
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

1443969

Citation

Campbell, N R., et al. "Ferrous Sulfate Reduces Thyroxine Efficacy in Patients With Hypothyroidism." Annals of Internal Medicine, vol. 117, no. 12, 1992, pp. 1010-3.
Campbell NR, Hasinoff BB, Stalts H, et al. Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism. Ann Intern Med. 1992;117(12):1010-3.
Campbell, N. R., Hasinoff, B. B., Stalts, H., Rao, B., & Wong, N. C. (1992). Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism. Annals of Internal Medicine, 117(12), 1010-3.
Campbell NR, et al. Ferrous Sulfate Reduces Thyroxine Efficacy in Patients With Hypothyroidism. Ann Intern Med. 1992 Dec 15;117(12):1010-3. PubMed PMID: 1443969.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism. AU - Campbell,N R, AU - Hasinoff,B B, AU - Stalts,H, AU - Rao,B, AU - Wong,N C, PY - 1992/12/15/pubmed PY - 1992/12/15/medline PY - 1992/12/15/entrez SP - 1010 EP - 3 JF - Annals of internal medicine JO - Ann Intern Med VL - 117 IS - 12 N2 - OBJECTIVE: To determine whether simultaneous ingestion of ferrous sulfate and thyroxine reduces the efficacy of thyroid hormone in patients with primary hypothyroidism. DESIGN: Uncontrolled clinical trial. SETTING: Outpatient research clinic of a tertiary care center. PATIENTS: Fourteen patients with established primary hypothyroidism on stable thyroxine replacement. INTERVENTION: All patients were instructed to ingest simultaneously, a 300-mg ferrous sulfate tablet and their usual thyroxine dose every day for 12 weeks. RESULTS: After 12 weeks of ferrous sulfate ingestion with thyroxine, the mean level of serum thyrotropin (thyroid stimulating hormone, TSH) rose from 1.6 +/- 0.4 to 5.4 +/- 2.8 mU/L (P < 0.01), but the free thyroxine index did not change significantly. Subjective evaluation using a clinical score showed that nine patients had an increase in symptoms and signs of hypothyroidism; the mean score for the 14 patients changed from 0 to 1.3 +/- 0.4 (P = 0.011). When iron and thyroxine were mixed together in vitro, a poorly soluble purple complex appeared that indicated the binding of iron to thyroxine. CONCLUSIONS: Simultaneous ingestion of ferrous sulfate and thyroxine causes a variable reduction in thyroxine efficacy that is clinically significant in some patients. The interaction is probably caused by the binding of iron to thyroxine. SN - 0003-4819 UR - https://www.unboundmedicine.com/medline/citation/1443969/full_citation L2 - https://www.acpjournals.org/doi/10.7326/0003-4819-117-12-1010?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -