**Core Concept**
Peptide hormones are a class of hormones that are composed of short chains of amino acids, typically consisting of 2-50 amino acid residues. These hormones are synthesized as preprohormones, which are then processed into prohormones, and eventually into mature peptide hormones. They are secreted by various glands and organs, including the pancreas, pituitary, thyroid, and adrenal glands.

**Why the Correct Answer is Right**
The correct answer is a peptide hormone because it is composed of a short chain of amino acids and plays a crucial role in regulating various physiological processes. For example, insulin, a peptide hormone produced by the pancreas, regulates glucose metabolism by facilitating the uptake of glucose by cells. It acts by binding to the insulin receptor, which triggers a cascade of intracellular signaling events that ultimately lead to the uptake of glucose by cells. Other examples of peptide hormones include growth hormone, adrenocorticotropic hormone (ACTH), and follicle-stimulating hormone (FSH).

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a steroid hormone, which is a class of hormones that are derived from cholesterol and play a crucial role in regulating various physiological processes, including metabolism, growth, and development.
**Option B:** This option is incorrect because it is a catecholamine, which is a class of hormones that are synthesized from the amino acid tyrosine and play a crucial role in regulating the body's "fight or flight" response.
**Option C:** This option is incorrect because it is a thyroid hormone, which is a type of hormone that is synthesized from the amino acid tyrosine and plays a crucial role in regulating metabolism.

**Clinical Pearl / High-Yield Fact**
Peptide hormones are often referred to as "trophic" hormones because they regulate the growth and development of various tissues and organs. For example, growth hormone stimulates the growth and development of bones, muscles, and other tissues, while insulin-like growth factor-1 (IGF-1) plays a crucial role in regulating the growth and development of bones and other tissues.

**Correct Answer: D. Growth hormone**