Question

Insulin-like growth factor (IGF) is secreted mainly by which organ?

• A. Liver
• B. Pituitary gland
• C. Pancreas
• D. Adrenal glands

Hint:

Growth hormone acts on this organ to make somatomedins.

Answer 1

The Correct Option is A

Step 1: Growth hormone (GH) is released by the anterior pituitary, but many of its growth-promoting actions are not direct. GH travels to the liver and stimulates it to produce small peptides called somatomedins.

Step 2: Because these somatomedins have actions similar to insulin, they are called insulin-like growth factors. The most important one is somatomedin C, also named IGF-1, which drives bone and tissue growth.

Step 3: IGF-1 binds to carrier proteins in blood, giving it a long half-life of about 20 hours versus roughly 20 minutes for GH. Its blood level tracks GH secretion.

Step 4: Since the liver is the principal site of IGF synthesis, the answer is liver. The pituitary makes GH (not IGF directly), the pancreas makes insulin, and the adrenal glands make steroids and catecholamines.