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Subclinical hypothyroidism – Quick review card

Subclinical hypothyroidism is elevated serum thyroid stimulating hormone ( TSH ) levels combined with normal levels of serum free thyroid hormone

 

a biochemical diagnosis – mostly picked on routine testing incidence between 3 % & 15 % ( Nazma et al report a prevalence of 3% to 8 % in the general population , this can be up to 15 % to 18 % in women > 60 ) incidence increases with age incidence of SCH varies by sex , age , race / ethnicity and geographic location higher rates of SCH are reported for women & older individuals it may be a transient phenomena ( change in TSH without thyroid disease ) it is not clear how SCH impacts general health ( for e.g relationship between SCH and adverse cardiac events or cardiac dysfunction , cognitive impairment , depression and the risk of fractures )

 

rate of progression for women with + ve TPO antibodies & a baseline TSH between 2.5 and 4 mIUl/ml is about 1 % other papers quote a rate of progression to clinically overt hypothyroidism at 2.6 % if TPO antibodies absent and 4.3 % if they are present rate of progression is significantly higher if TSH > 10 mIU/L

 

NICE recommends measuring TPOAbs ( thyroid peroxidase antibodies ) for adults with TSH above the reference range Do not repeat TPOAbs TPOAbs can be detected in 80 % of patients with SCH 80 % of patients with SCH have a TSH of < 10 mIU/l Considerable number of SCH cases may be transient or reversible in nature

 

patients with SCH have few or no symptoms or signs of thyroid dysfunction features that may suggest underlying thyroid disease ( hypothyroidism ) previous radioiodine treatment or thyroid surgery raised levels of thyroid autoantibodies transient SCH may occur after episodes of post partum , silent , and granulomatous throiditis

 

consider treatment if TSH is 10 mIU / l or higher on
 2 separate occasions 3 months apart 
○ aim to maintain TSH within the reference range
○ for people who had very high TSH before treatment started , it may take up to 6 months for the TSH to return to reference range

 

On 2 separate occasions, 3 months apart and they have symptoms of hypothyroidism

consider a 6 month trial in adults under 65

 

If symptoms do not improve re-check TSH and if raised adjust the dose TSH within range and symptoms persist – consider stopping and look at monitoring untreated SC hypothyroidism & monitoring after stopping treatment

 

TSH once a year if they have features of thyroid disease , h/o previous thyroid surgery or raised TPO antibodies OR once every 2-3 yrs if no features to suggest thyroid disease

REFERENCES

  1. Thyroid disease: assessment and management NICE guideline NG 145 Recommendations | Thyroid disease: assessment and management | Guidance | NICE
  2. Subclinical Hypothyroidism: Prevalence, Health Impact, and Treatment Landscape
    Won Sang Yoo, Hyun Kyung Chung Division of Endocrinology and Metabolism, Department of Internal Medicine, Dankook University College of Medicine, Cheonan, Korea *enm-2021-1066.pdf (e-enm.org)
  3. Akter, Nazma & Qureshi, Nazmul & Ferdous, Hossain. (2017). Subclinical Hypothyroidism: A Review on Clinical Consequences and Management Strategies. Journal of Medicine. 18. 30. 10.3329/jom.v18i1.31174.

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