Hormones are chemicals released in cells that affect other cells in the organism, this could be plant, or in our case, animal. In terms of human hormones they cover a wide range of different functions and act a chemical messenger sending a signal from one cell to another. In the human body, hormones are transferred through the blood or circulatory system.

Hormones can effect us in many ways, including Mood swings, hunger cravings (ghrelin, orexin and PYY3-36), as well as being instrumental in the inhibition, or promotion of growth in the human body.

Thus people who are of small stature, or are lacking adequate growth hormones, may have hormone replacement therapy to treat their condition.

Hormones can also affect our immune system, and consequently help or hindrance our immune system, much as can regulate our metabolic system, either speeding it up, or slowing it down. Thus having insufficient hormones required for immune support leads some patients to require anti-biotics for simple conditions, or use hormone growth cells to compensate for their lack of the bodies creation of adequate hormones.
                              

For women, it can also affect them for their reproductive cycle, child rearing, and menopause. Thus an inadequacy of certain hormones, such as dopamine, or an abundance of other hormones can create irritability during the menstrual cycle.

Human hormones include Dopamine, which increases our blood pressure, and our heart rate and is administered by the hypothalamus. Serotonin hormones affects our mood, appetite especially women during the menses cycle, as well as our sleep patterns and our ability to fall into a deep sleep.
    
Melatonin produced by our pineal gland, which is tucked away middle of the two brain sections. Melatonin affects our sleep pattern, and is what causes us to feel  drowsy. Ghrelin, as previously mentioned can stimulate our appetite as well as act a growth hormone secreted from our pituitary gland.

The pituitary gland is considered a master gland, as it secretes various other hormones, instrumental in the correct function of the human body. It is connected to the hypothalamus, which controls our hunger, thirst, fatigue levels, as well as managing our core body temperature. The pituitary gland controls our sex organs, and thus our sex drive, human growth, - as seen from the Ghrelin hormone - as well as in women for child-bearing functions, such as contractions during childbirth.