**1. Introduction**

Leptin is a 16 kDa non-glycosylated protein derived from adipose tissue, primarily by adipocytes. Leptin is a well-known mediator for food intake and weight loss [1]. Leptin mediates its functions mainly through the receptor located in the hypothalamus and activates signaling cascades associated with energy intake [2]. It circulates through the bloodstream, engages with normal metabolism, regulates energetic homeostasis, reproductive system, and influences the circadian cycle, lipid inflammation, and carbohydrate mechanisms. Leptin is well known for its pro-angiogenic potential and operates multiple signaling agencies through the receptor located in endothelial cells [3, 4]. Leptin is also secrets by other organs, such as the placenta, bone marrow, ovaries, stomach, and cellular structures, including mammary epithelial cells, P/D1 cells, and gastric chief cells [1]. Research has demonstrated that leptin plays a crucial role in maintaining the normal physiology of various vital systems such as the reproductive system and could balance cell proliferation (**Figure 1**). The pleiotropic hormone also could repair tissue damage and can prevent on-adipocyte lipotoxicity. Though leptin is highly acceptable for its protective mode of action, increased leptin level is often observed in several inflammatory

### **Figure 1.**

*Leptin exerts its pleiotropic impact on various organs. It maintains muscle tone and regulates cardiac function. Leptin regulates food intake and body weight management through binding with receptor located at brain. In the thyroid gland, leptin stimulates the secretion of TSH. In the female reproductive system, leptin manage menstrual cycle and supports in embryo implantation. Leptin inhibits insulin secretion and maintains blood-glucose level. Leptin induces sprouting of new vessels from existing ones and enhances ECs proliferation and migration and also it regulates bone metabolism and density.*

conditions [5]. Hence, a therapeutic approach based on leptin and receptor has become the need of the hour to balance many inflammatory diseases in the human body. The particular book chapter provides an insight into the multi-diversity properties of the pleiotropic hormone leptin.
