This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Male Reproductive System, Subject name: Physiology
Which of the following hormones is mainly responsible for skeletal maturation? 
Select and explain. 
A. Testosterone, B. Estrogen, C. Growth hormone, D. Insulin
A: Testosterone
Answer: A: Testosterone 
Explanation: Testosterone is a major factor responsible for the greater muscle mass and skeletal maturation. It has a myotrophic as well as androgenic (masculinization) action. Growth hormone increases skeletal and visceral growth. Insulin and thyroid hormones provide an additional stimulus for chondrocyte activity and growth of skeleton.