**Question:** Growth hormone has its effect on growth through

**Core Concept:** Growth hormone (GH) is a peptide hormone produced by the anterior pituitary gland, which plays a crucial role in stimulating growth, cell reproduction, and cell regeneration in humans and other mammals. GH acts on target tissues, such as the liver and cartilage, to promote the synthesis of insulin-like growth factor-1 (IGF-1), which is responsible for the growth-promoting effects of GH.

**Why the Correct Answer is Right:** Growth hormone stimulates growth primarily by acting on the liver, where it induces the production of insulin-like growth factor-1 (IGF-1). IGF-1 is a potent mitogen that promotes cell proliferation and differentiation, leading to increased tissue growth and regeneration. The correct answer (C) highlights the involvement of IGF-1 in the GH-mediated growth process, while options A, B, and D do not address the primary mechanism of GH action.

**Why Each Wrong Option is Incorrect:**

A. This option suggests that GH acts directly on growth plates to stimulate growth. While GH does have some effects on growth plates, the primary mode of action is through IGF-1 production.

B. This option incorrectly states that GH acts on the liver to increase insulin production. GH does not directly affect insulin levels but stimulates the liver to produce IGF-1.

D. This option incorrectly mentions that GH acts on the kidneys to maintain electrolyte balance. GH primarily affects growth through IGF-1, not renal electrolyte regulation.

**Clinical Pearl:** Understanding the role of IGF-1 in GH action is crucial for understanding growth and development in children and adults. A deficiency in GH or IGF-1 can lead to growth disorders, such as short stature in children and acromegaly in adults.

**Correct Answer:** C. Growth hormone acts on the liver to produce insulin-like growth factor-1 (IGF-1), which is responsible for the growth-promoting effects of GH.