Subclinical hyperthyroidism

• This advice advice relates to a finding of subclinical hyperthyroidism with a normal free T4 and a partially suppressed TSH (i.e. 0.1-0.35 mU/L).
• Transient subclinical hyperthyroidism can occur due to non-specific physical or psychiatric illness, drugs or pituitary causes and only requires specialist evaluation if persistent.
• We recommend repeating thyroid functions (TSH, TT3 and fT4) in 2-3 months and if the subclinical hyperthyroidism persists it would be useful to also check thyroid peroxidise (TPO) as well as thyrotropin receptor (TRAB) antibodies at that stage
• If TSH is persistently low then the patient has subclinical hyperthyroidism.
• The risk of progression to overt hyperthyroidism is very low at 0.6% over 7 years with 25-50% of levels normalising with long-term follow-up.

If the patient is 65 years of age or over AND they have any the following features please make a routine referral:

• Symptomatic of hyperthyroidism
• Have established atrial fibrillation or risk factors for atrial fibrillation (coronary or valvular heart disease, stroke etc.)
• History of osteoporosis

Treatment of people under 65 years of age is generally not recommended.

If the patient does not fall into any of the above categories then thyroid functions should be checked 6-12 monthly to ensure things have not progressed. We would not recommend review in clinic for this group.

• This advice relates to the finding of subclinical hyperthyroidism with a fully suppressed TSH (i.e. TSH<0.1mU/L) and normal FT4.
• Transient subclinical hyperthyroidism can occur due to non-specific physical or psychiatric illness, drugs or pituitary causes and only requires specialist evaluation if persistent.
• We would recommend re-checking thyroid functions in 2-3 months (TSH, TT3 and free T4). It would be useful to also check thyroid peroxidise (TPO) as well as thyrotropin receptor (TRAB) antibodies at that stage.
• If subclinical hyperthyroidism persists with a fully suppressed TSH then please refer to the endocrine team. The risk of progression to overt hyperthyroidism is increased with full TSH suppression, at 5-8% per year.
• Treatment will be considered in those with suggestive symptoms, those aged over 65 years and for those at risk of atrial fibrillation or low bone mineral density