Also known as the "starvation hormone", leptin signals the hypothalamus that the body has enough fat stored to function normally. When leptin levels are high enough, appetite is inhibited. When leptin levels are low, it indicates that we need to consume more food and appetite increases.

Cortisol is released by the adrenal cortex, which is controlled by the hypothalamus and anterior pituitary. The hypothalamus releases corticotropin-releasing hormone, triggering the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary gland. ACTH stimulates the release of cortisol. Cortisol is released when the body is under long-term stress, such as malnutrition, dehydration, or prolonged mental stress.

The pineal gland secretes serotonin by day and converts it to melatonin at night. These chemicals affect mood, anxiety, and sleep. The pineal gland may also play a role in seasonal affective disorder, in which people are depressed during the darker days of winter. Selective serotonin reuptake inhibitors (SSRIs) are a class of drug that work to elevate mood by blocking the cells that breakdown serotonin, leaving it in the synapses of the nervous system for a longer period of time.

Dopamine has a neuromuscular function, as an absence is associated with Parkinson's disease. Norepinephrine has a stimulatory effect. Acetylcholine stimulates muscle cells to contract. Endorphins are the body's natural pain relievers. 

Epinephrine, also called adrenaline, is a hormone that activates the sympathetic nervous system. This triggers our "fight or flight" response, which increases heart rate, dilates the pupil, increases blood flow to skeletal muscle, and reduces digestive and reproductive activity.

The pituitary gland is considered the "master gland" of the endocrine system. Hormones secreted from the pituitary gland help regulate growth, metabolism, and numerous other bodily functions and processes. The medulla oblongata is the part of the brainstem located just above the spinal chord. 

The thymus, located in the chest, is primarily responsible for secreting hormones involved with healthy immune system development. This development happens during puberty and continues afterwards.

The endocrine system is a system of glands that secretes hormones into the circulatory system. These hormones are directed to organs that control growth and development, reproduction, and body metabolism. It is a system that links the brain to these organs. 

The endocrine system is a system of glands that secretes hormones into the circulatory system. These glands include the ovaries and testes, the pituitary gland, the thyroid, and pineal glands and many others, all of which control growth and development, reproduction, and body metabolism.

The endocrine system, in tandem with the central nervous system and immune system, plays a central role in maintaining a state of homeostasis throughout the body. Diseases of the endocrine system are, however, common and include diseases of the thyroid and diabetes mellitus. 

The ovaries, an essential part of the female reproductive system, are responsible for producing estrogen and progesterone.