<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 35-year-old woman comes to the physician because of a 3-month history of headache, palpitations, diarrhea, and weight loss. She takes no medications. Her pulse is 110min and blood pressure is 12570 mm Hg. Examination shows warm, moist skin and diffuse hyperreflexia. An MRI of the brain shows a sellar mass. The underlying cause of this patients condition is best explained by binding of a ligand to which of the following?? A: Intracytosolic nuclear receptor, B: Receptor tyrosine kinase, C: G protein-coupled receptors, D: Membrane-bound guanylate cyclase, E: Nonreceptor tyrosine kinase,  <response>: This is a clinical vignette describing a patient with symptoms of headache, palpitations, diarrhea, weight loss, tachycardia, and hypertension. The key finding is a sellar mass on MRI of the brain, which indicates a pituitary tumor. The question asks about the underlying cause being explained by binding of a ligand to a specific receptor type. Based on the clinical presentation, this is most consistent with hypersecretion of hormones from the pituitary tumor. The options describe different receptor types. Receptor tyrosine kinases B and nonreceptor tyrosine kinases E are not typically involved in pituitary hormone secretion. Intracytosolic nuclear receptors A and membrane-bound guanylate cyclases D also do not fit with the clinical scenario. G protein-coupled receptors C activate second messenger systems and are involved in the mechanism of action of many pituitary hormones. This is the most likely receptor type involved in the underlying pathology.C: G protein-coupled receptors 