This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology metabolism, Subject name: Physiology
Cell surface receptors are used by which hormone- 
Select and explain. 
A. Thyroxine, B. Testosterone, C. Glucagon, D. Cortisol
C: Glucagon
Answer: C: Glucagon 
Explanation: Ans. is 'c'i.e., Glucagon Type of receptorso All hormones act through specific receptors present inside the cell (intracellular) or on the surface of cells (membrane receptors).A. Membrane receptorso Present on the cell membrane.o Their drug/hormone binding domain is extracellular and effector domain is intracellular.These are:1. G protein coupled receptors - It may act through.a) Adenylyl cyclase| cAMP - TSH, FSH, LH, ACTH, glucagon, PTH, adrenaline, calcitonin, vasopressin (V2).| cAM P - PRIH (Dopamine)b) IP3-DAG (Ca2+ and protein kinase 'c') -Vasopressin (V1), oxytocin.c) Channel regulation (Ca+2, K+ Na+)2. Receptor with Intrinsic ion channels - (Na+, K+, Ca+2 or C1-)3. Enzyme linked receptorsa) Intrinsic enzyme receptors (tyrosine kinase receptors) - Insulin.b) JAK-STAT kinase binding receptors - Growth hormone, Prolactin.B. Intracellular receptors (transcription factors)o Present inside the cell and induce synthesis of specific protein by increasing the expression of specific gene.1. Cytoplasmic - Glucocorticoids, Mineralocorticoids, Androgens, Progestins.2. Nuclear - Thyroxine, Triiodothyronine, Estrogen, retinoic acid, Vit D.