1st April 2022

A 42-year-old female presents with 3 months history of feeling restless

A 42-year-old female presents with 3 months history of feeling restless, like her “heart’s about t0 beat out of [her] chest”, and diarrhoea. She has a past medical history of type 1 diabetes mellitus, controlled by insulin. On examination, there is a fine tremor and clubbing in the hands, exophthalmos, and smooth goitre. 

The presence of which biomarker is most likely to give the definitive diagnosis?

Select the SINGLE most appropriate option from the list below. Select ONE option only.