Overview
Subclinical hypothyroidism describes an elevated thyroid-stimulating hormone (TSH) with normal free T4 (FT4) and free T3 (FT3).
Epidemiology
- More common in women
- 10% of women over 55 years may have subclinical hyperthyroidism
Diagnosis
Overview
Thyroid function tests (TFTs) show elevated TSH and normal FT4 and FT3. These should be repeated after 3 months to exclude other causes of transiently raised TSH.
Thyroid peroxidase antibody (TPOAb) testing may be considered. If positive, this can predict progression to overt hypothyroidism.
Management
Overview
As long as subclinical hypothyroidism is diagnosed as above:
- TSH >10 mU/L: consider offering levothyroxine
- TSH 5.5 – 10 mU/L:
- If <65 years old and symptoms of hypothyroidism: 6-month trial of levothyroxine
- In older people: watch and wait
- If asymptomatic: observe and repeat TFTs in 6 months
Complications
- Progression to overt hypothyroidism
- Cardiovascular disease:
- Hypercholesterolaemia
- Hypertension
- Decreased muscle strength
- Fatigue
- Cognitive impairment
