In a situation where P450 enzymes are regulated by GH, how would an absence of GH affect drug metabolism?

• A. Enhance metabolic rate
• B. Inhibit drug metabolism
• C. No effect on metabolism
• D. Increase drug potency

Answer: (B)

The correct answer is that the absence of growth hormone (GH) would inhibit drug metabolism. P450 enzymes, also known as cytochrome P450 enzymes, are crucial for the metabolism of a wide variety of drugs and other xenobiotics in the liver. These enzymes are regulated by several factors, one of which is GH.

GH promotes the expression and activity of certain P450 enzymes, which facilitates the breakdown and elimination of drugs from the body. Therefore, when GH levels are low or absent, the expression and activity of these enzymes are diminished, leading to a reduced metabolic rate for drugs. This results in slower clearance of medications and can increase the potential for drug accumulation and toxicity.

In this context, a decrease in drug metabolism can lead to prolonged drug action and potentially harmful side effects due to higher plasma concentrations of the drug over time. Thus, the absence of GH directly inhibits the normal metabolic processes mediated by P450 enzymes.