This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and Reproduction, Subject name: Physiology
[{'content': 'Which is true about Sex hormone-binding globulin (SHBG): \nSelect and explain. \nA. Binds testosterone with a higher affinity than estradiol, B. Reduces the total amount of circulating testosterone, C. Decreases the half-life of testosterone, D. Stimulates the secretion of inhibin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: And. A. Binds testosterone with a higher affinity than estradiolSex hormone-binding globulin binds to both testosterone and estradiol, but it binds with higher affinity to testosterone. The bioactivity of testosterone is reduced by SHBG because testosterone cannot bind to its receptor when bound by SHBG. SHBG increases the circulating half-life of testosterone by slowing the clearance and metabolism of testosterone. SHBG does not alter the secretion of inhibin or androgen-binding protein, area', 'role': 'assistant'}]