This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
The best marker to diagnose thyroid related disorders is- 
Select and explain. 
A. T3, B. T4, C. TSH, D. Thyroglobulin
C: TSH
Answer: C: TSH 
Explanation: Answer is option 3 TSH The enhanced sensitivity and specificity of TSH assays have greatly improved laboratory assessment of thyroid function. Normal TSH excludes primary abnormalities of thyroid mostly. Ref Harrison 19e /p2283