Which of the following is influenced by growth hormone?

• A. All of these
• B. IGF-I
• C. IGFBP-III
• D. Lipolysis

Answer: (A)

Growth hormone has multiple metabolic actions, not just one. It stimulates production of IGF-I in the liver and other tissues, which is a major mediator of GH’s growth-promoting and metabolic effects. It also increases IGF-binding protein 3 (IGFBP-III), the main carrier that regulates IGF activity and half-life in the blood. In addition, GH promotes lipolysis in adipose tissue by activating hormone-sensitive lipase, raising circulating free fatty acids for energy. Because growth hormone influences all three processes, the best answer is the one that encompasses every listed effect.