**Core Concept**
Normal growth in children is a complex process involving the coordinated efforts of multiple hormones and growth factors. The growth hormone (GH) secreted by the pituitary gland plays a crucial role in regulating growth and development by stimulating the production of insulin-like growth factor-1 (IGF-1) in the liver and other tissues.

**Why the Correct Answer is Right**
The correct answer is related to the regulation of growth hormone secretion. GH is produced by the somatotrophs in the anterior pituitary gland and is released in a pulsatile manner throughout the day. The growth hormone-releasing hormone (GHRH) from the hypothalamus stimulates the release of GH, while the somatostatin inhibits its release. IGF-1, produced in response to GH, mediates many of its effects on growth and development.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify a factor required for normal growth.
* **Option B:** This option is incorrect because it is not directly related to the regulation of growth hormone secretion.
* **Option C:** This option is incorrect because it is not a hormone involved in the regulation of growth.

**Clinical Pearl / High-Yield Fact**
The growth hormone secretion is regulated by a negative feedback loop, where IGF-1 produced in response to GH inhibits the release of GHRH, thereby reducing GH production.

**Correct Answer:** D.