J Korean Med Sci.  2013 Nov;28(11):1622-1626. 10.3346/jkms.2013.28.11.1622.

Prospective Observation of 5-Year Clinical Course of Subclinical Hypothyroidism in Korean Population

• Park WR
• Oh TK
• Jeon HJ

• KMID: 1777659
• DOI: http://doi.org/10.3346/jkms.2013.28.11.1622

Abstract

Subclinical hypothyroidism (SCH) is a common clinical condition, whereas it's natural course has not been identified distinctly. We evaluated the natural history of 169 SCH patients over 5-yr and the prognostic factors including thyroid autoantibodies and thyroid ultrasonographic (USG) findings related to develop overt hypothyroidism. After 5 yr, 47.3% of patients showed normalization of TSH, while 36.7% of patients remained persistence of high level of TSH, and overt hypothyroidism developed in 11.2% of patients. There were painless thyroiditis (2.9%) and hyperthyroidism (1.7%) during 5 yr follow-up. The thyroid nodule was seen in 48.6% of patients. Most of patients had 1 to 2 nodules whereas only 3% of patients with thyroid nodule had more than 6 nodules. Overt hypothyroidism patients had more heterogenous echogenecity in USG compared to patients with normalization or persistent SCH (76.5% vs 50.0% vs 35.0%, P = 0.048) and higher prevalence positive anti-thyroid peroxidase (anti-TPO Ab) and anti-thyroglobulin antibody (anti-Tg Ab) and titer of anti-TPO Ab than other two groups. The cut off values for prediction of overt hypothyroidism were TSH > 7.45 microIU/mL, free T4 < 1.09 ng/dL and Anti-TPO Ab > 560 IU/mL. SCH has various courses and initial TSH, free T4, presence of thyroid autoantibody, titer of thyroid autoantibody; and thyroid USG findings can serve as a prognostic factor for progression of overt hypothyroidism. These parameters suggest consideration to initiate thyroid hormone treatment in SCH.

Keyword

Subclinical Hypothyroidism; Natural History; Hypothyroidism

MeSH Terms

Asymptomatic Diseases/*epidemiology
Autoantibodies/blood/immunology
Disease Progression
Female
Humans
Hyperthyroidism/epidemiology
Hypothyroidism/*epidemiology
Male
Middle Aged
Prevalence
Prospective Studies
Republic of Korea/epidemiology
Thyroglobulin/immunology
Thyroid Function Tests
Thyroid Gland/immunology
Thyroid Nodule/epidemiology
Thyroiditis/epidemiology
Thyrotropin/*blood
Autoantibodies
Thyroglobulin
Thyrotropin

Figure

• 

  Fig. 1 Incidence of thyroid dysfunction. TSH, Thyroid stimulating hormone; SCH, Subclinical hypothyroidism.

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