A person with dwarfism is found to have normal levels of circulating Growth Hormone (GH) and has fully functioning kidneys capable of producing sufficient levels of insulin-like growth factors (IGF-I, IGF-II). What is one reason why this person could still be a dwarf?
A) Prolactin deficiency
B) Non-functional GH binding receptors on the kidneys
C) Excess levels of IGF-I
D) Excess levels of IGF-II
E) Overactive hypothalamus

Question

Quizplus · Accepted Answer

The reason for dwarfism in this scenario could be non-functional GH binding receptors on the kidneys. Even if GH and IGF levels are normal, GH must bind to its receptors to exert its effects, including stimulating the production of IGFs in the liver (not kidneys as mentioned, but the principle of GH receptor functionality applies broadly). If GH receptors are non-functional, this signaling pathway is disrupted, leading to conditions affecting growth, such as dwarfism.

A Person with Dwarfism Is Found to Have Normal Levels