Function of leptin is-
**Core Concept**
Leptin is a hormone produced by fat cells (adipocytes) that plays a crucial role in energy balance and metabolism. It acts as a key regulator of appetite, satiety, and body weight by interacting with the hypothalamus in the brain.
**Why the Correct Answer is Right**
Leptin's primary function is to signal the body about its energy status, particularly fat reserves. When leptin levels are high, it inhibits appetite and increases metabolism, indicating that the body has sufficient energy stores. Conversely, low leptin levels stimulate appetite and decrease metabolism, prompting the body to seek energy sources. Leptin acts through the leptin receptor (LEPR) in the hypothalamus, activating the JAK-STAT signaling pathway, which ultimately influences the expression of genes involved in energy homeostasis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the primary function of leptin.
**Option B:** This option is incorrect because leptin is not primarily involved in the regulation of blood pressure.
**Option C:** This option is incorrect because leptin is not directly involved in the regulation of thyroid hormone levels.
**Clinical Pearl / High-Yield Fact**
Leptin deficiency or resistance is associated with obesity, particularly visceral obesity, which is linked to an increased risk of metabolic syndrome, type 2 diabetes, and cardiovascular disease.
**Correct Answer: C. Regulation of energy balance and body weight through appetite and metabolism.**