What work up do you recommend for persistent subclinical hyperthyroidism with decreased RAI uptake and negative thyroid antibody tests?  

If the RAIU is very low, then this may be subacute thyroiditis. Lymphocytic or silent has no biochemical confirmatory tests. If there is pain, this suggest pseudogranulomatis subacute thyroiditis associated with a high URI and a recent viral infection. The other choice is they have some nodular thyr...