This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrine System, Subject name: Physiology
[{'content': 'If a radioimmunoassay is properly conducted and the amount of radioactive hormone bound to antibody is low, what would this result indicate? \nSelect and explain. \nA. Plasma levels of endogenous hormone are high, B. Plasma levels of endogenous hormone are low, C. More antibody is needed, D. Less radioactive hormone is needed', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In a radioimmunoassay, there is too little antibody to completely bind the radioactively tagged hormone and the hormone in the fluid (plasma) to be assayed. Thus, there is competition between the labeled and endogenous hormone for binding sites on the antibody. Consequently, if the amount of radioactive hormone bound to antibody is low, this finding would indicate that plasma levels of endogenous hormone are high', 'role': 'assistant'}]