Abnormal TSH with normal thyroid hormone

Subclinical hypothyroidism

• ↑TSH, normal fT4/3
• Risk of progression to overt hypothyroidism
• Higher risk if strongly TPO antibody positive
• Treatment generally advised if TSH > 10
• Always treat in pregnancy to maintain normal TSH

Subclinical hyperthyroidism

• ↓TSH, normal fT4/3
• Risk of progression to overt hyperthyroidism
• Often seen in multi-nodular goitre
• Association with osteoporosis and atrial fibrillation
• Treatment generally advised if TSH <0.1% (or if co-existing osteoporosis/fracture or AF)