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subclinical hyperthyroidism

Etiology: 1) toxic multinodular goiter (most common) [1] 2) associated conditions a) old age b) early in pregnancy c) acute psychiatric illness d) systemic illness (transient) 3) pharmaceutical agents a) dopamine b) corticosteroids Clinical manifestations: - patients are asymptomatic Laboratory: 1) normal levels of serum free T4, serum free T3 2) diminished levels of serum TSH 3) repeat serum TSH & serum free T4 - in 4-6 months if serum TSH > 0.1 mIU/mL & asymptomatic [1] - in 6-8 weeks if serum TSH > 0.1 mIU/mL or symptomatic & treated Radiology: - increased radioactive iodine uptake - hyperfunctioning nodules may be observed Complications: 1) three fold increased risk of developing atrial fibrillation 2) tachycardia 3) cardiomegaly 4) loss of bone mineral density in postmenopausal women - increased risk of hip fracture in men (HR=3.3), but not omen [4] - increased risk of fracture, including hip fracture in both men & women (RR=1.2-1.3) [7] - risk of fracture higher at lower serum TSH [7] 5) increased cardiovascular risk & risk of mortality [5] 6) no increased risk of cognitive impairment [12] 7) no increased risk of fractures [13] Management: 1) decision to treat is controversial [1] 2) USPSTF recommendations [2] a) NO treatment if serum TSH > 0.1 mIU/mL [2] b) if serum TSH < 0.1 mIU/mL 1] good evidence of risk for progression to overt hyperthyroidism & atrial fibrillation 2] treatment if serum TSH < 0.1 mIU/mL & cardiac risk factors, heart disease, high risk for osteoporosis or symptoms [1] 3] no data to support treatment to prevent these outcomes c) low serum TSH normalizes within 5 years after initial testing in most children [3] d) is transient in up to 50% of patients [11] 3) no treatment indicated unless persistent (> 4-6 months) & serum TSH < 0.1 uIU/mL & symptoms, cardiovascular disease , osteoporosis, or postmenopausal women not taking bisphosphonate or estrogen replacement therapy [1] - treatment of toxic multinodular goiter is with methimazole prior to radioactive I-131 ablation of thyroid [1] - refer to endocrinologist for treatment [1] 4) low serum TSH normalizes in 50% without intervention [11]

Related

euthyroid sick syndrome; nonthyroidal illness syndrome; low T3 syndrome (ESS) subclinical hypothyroidism

General

hyperthyroidism subclinical thyroid disease

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 17, 18, 19. American College of Physicians, Philadelphia 1998, 2006, 2015, 2018, 2022. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  2. Journal Watch 24(5):41, 2004 US Preventive Services Task Force (USPSTF), Ann Intern Med 140:125, 2004 http://www.ahrq.gov/clinic/3rduspstf/thyroid/thyrrs.htm Helfand M, Ann Intern Med 140:128 PMID: 14734337 http://www.endo-society.org/education/evidence-report.cfm - Surks MI et al Subclinical thyroid disease: scientific review and guidelines for diagnosis and management. JAMA 291:228, 2004 PMID: 14722150
  3. Lazar L et al Natural history of thyroid function tests over 5 years in a large pediatric cohort. J Clin Endocrinol Metab 2009 May; 94:1678 PMID: 19240148
  4. Lee JS et al. Subclinical thyroid dysfunction and incident hip fracture in older adults. Arch Intern Med 2010 Nov 22; 170:1876 PMID: 21098345
  5. Collet T-H et al Subclinical Hyperthyroidism and the Risk of Coronary Heart Disease and Mortality Arch Intern Med. Published online April 23, 2012 PMID: 22529182 http://archinte.ama-assn.org/cgi/content/full/archinternmed.2012.402 - Burman KD What Is the Clinical Importance of Subclinical Hyperthyroidism? Arch Intern Med. Published online April 23, 2012 PMID: 22529181 http://archinte.ama-assn.org/cgi/content/short/archinternmed.2012.1114
  6. Donangelo I1, Braunstein GD. Update on subclinical hyperthyroidism. Am Fam Physician. 2011 Apr 15;83(8):933-8. PMID: 21524033
  7. Blum MR et al Subclinical Thyroid Dysfunction and Fracture RiskA Meta-analysis. JAMA. 2015;313(20):2055-2065 PMID: 26010634 http://jama.jamanetwork.com/article.aspx?articleid=2297170
  8. Biondi B Natural history, diagnosis and management of subclinical thyroid dysfunction. Best Pract Res Clin Endocrinol Metab. 2012 Aug;26(4):431-46. PMID: 22863386
  9. Cooper DS, Biondi B. Subclinical thyroid disease. Lancet. 2012 Mar 24;379(9821):1142-54. Review. PMID: 22273398
  10. Vadiveloo T, Donnan PT, Cochrane L, Leese GP The Thyroid Epidemiology, Audit, and Research Study (TEARS): the natural history of endogenous subclinical hyperthyroidism. J Clin Endocrinol Metab. 2011 Jan;96(1):E1-8. PMID: 20926532
  11. Rothaus C NEJM Resident 360. June 2018 https://resident360.nejm.org/content_items/subclinical-hyperthyroidism
  12. van Vliet NA, van Heemst D, Almeida OP et al. Association of thyroid dysfunction with cognitive function: An individual participant data analysis. JAMA Intern Med 2021 Sep 7; [e-pub]. PMID: 34491268 PMCID: PMC8424529 Free PMC article https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2783799
  13. Daya NR et al. Association between subclinical thyroid dysfunction and fracture risk. JAMA Netw Open 2022 Nov 8; 5:e2240823. PMID: 36346629 Free article. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2798206