This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pathology
[{'content': 'Senile cardiac amyloid associated protein is \nSelect and explain. \nA. Transthyretin, B. ANP, C. Beta 2 microglobulin, D. Gelsolin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Transthyretin (TTR) is a normal serum protein that binds and transpos thyroxine and retinol. Several distinct mutant forms of TTR (and its fragments) are deposited in a group of genetically determined disorders referred to as familial amyloid polyneuropathies. Normal TTR is also deposited in the hea of aged individuals (senile systemic amyloidosis)Reference: Robbins and Cotran Pathologic Basis of Disease; 9th edition; Chapter 6; Diseases of the Immune System', 'role': 'assistant'}]