All of the following statements about insulin like growth factor -(IGF) are true, except(2018)
**Core Concept**
Insulin-like growth factor-1 (IGF-1) is a protein that plays a crucial role in cell proliferation, differentiation, and survival. It is a key mediator of growth hormone's (GH) effects on various tissues, including bone, cartilage, and liver.
**Why the Correct Answer is Right**
IGF-1 binds to its receptor (IGF-1R) on the cell surface, triggering a cascade of intracellular signaling pathways that promote cell growth and survival. IGF-1 also has a role in glucose and lipid metabolism, and its levels are often elevated in conditions such as acromegaly, a disorder caused by excess GH production. The liver is a primary site of IGF-1 production, and its levels are regulated by GH.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because IGF-1 is indeed involved in glucose metabolism, but its primary role is not as a glucose transporter. It can, however, modulate glucose uptake in certain tissues.
**Option B:** Incorrect because IGF-1 does have a role in lipid metabolism, particularly in the regulation of lipolysis and lipogenesis. However, its effects on lipid metabolism are more indirect than those of GH.
**Option C:** Incorrect because while IGF-1 does have a role in bone growth and development, its primary function is not to regulate bone resorption. Instead, it promotes bone formation and chondrocyte differentiation.
**Clinical Pearl / High-Yield Fact**
IGF-1 levels are often used as a biomarker for GH excess or deficiency, and its measurement can help diagnose conditions such as acromegaly or growth hormone deficiency.
**Correct Answer: B. IGF-1 does not regulate glucose transport directly.**