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
Which hormone receptor has 4 subunits and 2 units for tyrosine kinase receptor binding? 
Select and explain. 
A. Insulin, B. Glucagon, C. T3, D. ADH
A: Insulin
Answer: A: Insulin 
Explanation: Ans. A InsulinRef: Ganong, 25th ed. pg. 434Insulin receptor is a tetramer made of two alpha and two beta glycoprotein proteins. The alpha subunits bind insulin and are extracellular while beta subunits have tyrosine kinase activity. The growth promoting anabolic effects of insulin are mediated by phosphatidyl inositol kinase pathway.