**Core Concept**
Neuropeptide Y (NPY) is a potent stimulator of appetite and energy storage, playing a crucial role in regulating food intake and energy metabolism. It is a member of the pancreatic polypeptide family and has 36 amino acids.

**Why the Correct Answer is Right**
NPY is known to increase appetite and promote fat storage by stimulating the release of insulin and suppressing the release of glucagon. It also decreases thermogenesis, which is the process of heat production in the body, by inhibiting the activity of brown adipose tissue. This makes it a key player in the regulation of energy balance and body weight.

**Why Each Wrong Option is Incorrect**
* **Option A:** Neuropeptide Y indeed consists of 36 amino acids, making this statement true.
* **Option B:** NPY is known to decrease thermogenesis, which is the process of heat production in the body, so this statement is also true.
* **Option C:** During starvation, the levels of NPY actually increase, not decrease, as the body tries to conserve energy and promote food intake, making this statement false.
* **Option D:** Melanocorticotropin, also known as alpha-melanocyte-stimulating hormone (α-MSH), has opposite effects to NPY, as it decreases appetite and increases thermogenesis, making this statement false.

**Clinical Pearl / High-Yield Fact**
NPY is often referred to as the "hunger hormone" due to its potent stimulatory effects on appetite and food intake. This makes it a key target for the development of anti-obesity therapies.

**Correct Answer:** C. Decreased in starvation