Question

A healthy, well-nourished 4-year-old boy whose height is that of a 2-year-old child has an increased serum growth hormone concentration and a decreased serum insulin-like growth factor-1 (IGF-1) concentration. This patient's hepatocytes most likely contain decreased phosphorylated quantities of which of the following?

A) Growth hormone receptor-linked G protein
B) Growth hormone receptor serine
C) Growth hormone receptor tyrosine
D) 1GF−1 receptor-linked G protein
E) 1GF−1 receptor serine
F) 1GF−1 receptor tyrosine

Answer 1

In the case presented, due to the increased serum growth hormone and decreased IGF-1 levels, it is likely that the hepatocytes contain decreased phosphorylated quantities of growth hormone receptor tyrosine.

Step-by-step explanation:

The patient described likely has an altered response to growth hormone (GH) due to a disruption in the GH signaling pathway. GH exerts its effects directly and indirectly, with the indirect effects mediated by insulin-like growth factor-1 (IGF-1) which is a growth-promoting protein produced by the liver.

Normally, GH binds to its receptor on the hepatocyte cell surface, causing receptor tyrosine phosphorylation, which then triggers a cascade of intracellular events leading to the production of IGF-1. If serum IGF-1 levels are low despite elevated levels of GH, this suggests a problem in the GH pathway at the liver, specifically in the GH receptor signal transduction leading to IGF-1 production. Therefore, the hepatocytes most likely contain decreased phosphorylated quantities of growth hormone receptor tyrosine (option C).