Subclinical hypothyroidism
In medicine, subclinical hypothyroidism is an elevated thyrotropin (TSH) concentration can maintain a normal or near normal thyroxine (T4) concentration.[1][2]
Prognosis
"Subclinical hypothyroidism is associated with an increased risk of CHD events and CHD mortality in those with higher TSH levels, particularly in those with a TSH concentration of 10 mIU/L or greater" according to a individual patient data meta-analysis. [3]
Thyrotropin level
| Follow-up TSH value | ||
|---|---|---|
| TSH > 10 | TSH < 10 | |
| TSH > 10 | 35% | 64% |
| TSH 5.5 - 10 | 3% | 97% |
The thyrotropin level helps predict progression to overt hypothyroidism.[4]
Antithyroid peroxidase antibodies
Antithyroid peroxidase (also called antithyroid microsomal) antibodies my help predict progression to overt hypothyroidism.[5][6][7]
Diagnostic accuracy for predicting over hypothyroidism has been reported.
Diez et al found that among patients with TSH > 5, antibodies > 20 U/ml were significant predictors of hypothyrodism after 3.5 years of follow-up in which 26% developed overt hypothyroidism, but not after controlling for initial thyrotropin level.[7]
- Sensitivity 93%
- Specificity 30%
- Positive predictive value 32%
- Negative predictive value 92%
Walsh et al found that among patients with TSH> 4, antibodies > 35 U/ml were significant predictors of hypothyrodism after 13 years of follow-up in which 31% developed overt hypothyroidism, but not after controlling for initial thyrotropin level.[5]
- Sensitivity 84%
- Specificity 30%
- Positive predictive value 60%
- Negative predictive value 60%
Treatment
"In current RCTs, levothyroxine replacement therapy for subclinical hypothyroidism did not result in improved survival or decreased cardiovascular morbidity" according to a meta-analysis by the Cochrane Collaboration. [8] Subsequent randomized controlled trials have been positive using 100 microg T4 orally per day[9] and negative using 25 microg T4 orally per day[10].
Screening
The US Preventive Services Task Force states:[11]
- "t is uncertain whether treatment will improve quality of life in otherwise healthy patients who have abnormal TSH levels and normal free thyroxine levels."
References
- ↑ Surks MI, Ortiz E, Daniels GH, Sawin CT, Col NF, Cobin RH et al. (2004). "Subclinical thyroid disease: scientific review and guidelines for diagnosis and management.". JAMA 291 (2): 228-38. DOI:10.1001/jama.291.2.228. PMID 14722150. Research Blogging.
- ↑ Cooper DS, Biondi B (2012). "Subclinical thyroid disease.". Lancet 379 (9821): 1142-54. DOI:10.1016/S0140-6736(11)60276-6. PMID 22273398. Research Blogging.
- ↑ Rodondi N, den Elzen WP, Bauer DC, Cappola AR, Razvi S, Walsh JP et al. (2010). "Subclinical hypothyroidism and the risk of coronary heart disease and mortality.". JAMA 304 (12): 1365-74. DOI:10.1001/jama.2010.1361. PMID 20858880. Research Blogging. Review in: Evid Based Med. 2011 Feb;16(1):31-2
- ↑ 4.0 4.1 Meyerovitch J, Rotman-Pikielny P, Sherf M, Battat E, Levy Y, Surks MI (2007). "Serum thyrotropin measurements in the community: five-year follow-up in a large network of primary care physicians.". Arch Intern Med 167 (14): 1533-8. DOI:10.1001/archinte.167.14.1533. PMID 17646608. Research Blogging.
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<ref>tag; name "pmid17646608" defined multiple times with different content - ↑ 5.0 5.1 Walsh JP, Bremner AP, Feddema P, Leedman PJ, Brown SJ, O'Leary P (2010). "Thyrotropin and thyroid antibodies as predictors of hypothyroidism: a 13-year, longitudinal study of a community-based cohort using current immunoassay techniques.". J Clin Endocrinol Metab 95 (3): 1095-104. DOI:10.1210/jc.2009-1977. PMID 20097710. Research Blogging.
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<ref>tag; name "pmid20097710" defined multiple times with different content - ↑ Li Y, Teng D, Shan Z, Teng X, Guan H, Yu X et al. (2008). "Antithyroperoxidase and antithyroglobulin antibodies in a five-year follow-up survey of populations with different iodine intakes.". J Clin Endocrinol Metab 93 (5): 1751-7. DOI:10.1210/jc.2007-2368. PMID 18270254. Research Blogging.
- ↑ 7.0 7.1 Díez JJ, Iglesias P (2004). "Spontaneous subclinical hypothyroidism in patients older than 55 years: an analysis of natural course and risk factors for the development of overt thyroid failure.". J Clin Endocrinol Metab 89 (10): 4890-7. DOI:10.1210/jc.2003-032061. PMID 15472181. Research Blogging.
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<ref>tag; name "pmid15472181" defined multiple times with different content - ↑ Villar HC, Saconato H, Valente O, Atallah AN (2007). "Thyroid hormone replacement for subclinical hypothyroidism.". Cochrane Database Syst Rev (3): CD003419. DOI:10.1002/14651858.CD003419.pub2. PMID 17636722. Research Blogging. Review in: ACP J Club. 2008 Jan-Feb;148(1):7 Review in: ACP J Club. 2008 Jan-Feb;148(1):6 Review in: Evid Based Med. 2008 Feb;13(1):22
- ↑ Razvi S, Ingoe L, Keeka G, Oates C, McMillan C, Weaver JU (2007). "The beneficial effect of L-thyroxine on cardiovascular risk factors, endothelial function, and quality of life in subclinical hypothyroidism: randomized, crossover trial.". J Clin Endocrinol Metab 92 (5): 1715-23. DOI:10.1210/jc.2006-1869. PMID 17299073. Research Blogging.
- ↑ Parle J, Roberts L, Wilson S, Pattison H, Roalfe A, Haque MS et al. (2010). "A randomized controlled trial of the effect of thyroxine replacement on cognitive function in community-living elderly subjects with subclinical hypothyroidism: the Birmingham Elderly Thyroid study.". J Clin Endocrinol Metab 95 (8): 3623-32. DOI:10.1210/jc.2009-2571. PMID 20501682. Research Blogging.
- ↑ Helfand M, U.S. Preventive Services Task Force (2004). "Screening for subclinical thyroid dysfunction in nonpregnant adults: a summary of the evidence for the U.S. Preventive Services Task Force.". Ann Intern Med 140 (2): 128-41. PMID 14734337. [e]