The endocrine system, made up of hormone-secreting glands, also affects communication inside the body. Hormones are chemicals that help to regulate bodily functions. The glands produce hormones and dump them into the bloodstream, through which the hormones travel to various parts of the body. Hormones act more slowly than neurotransmitters, but their effects tend to be longer lasting.
The pituitary gland, which lies close to the hypothalamus of the brain, is often called the master gland of the endocrine system. When stimulated by the hypothalamus, the pituitary gland releases various hormones that control other glands in the body. The chart below summarizes the better known hormones along with some of their functions.
|Hormone||Produced by||Involved in regulating|
|Thyroxine||Thyroid gland||Metabolic rate|
|Insulin||Pancreas||Level of blood sugar|
|Melatonin||Pineal gland||Biological rhythms, sleep|
|Cortisol, Norepinephrine, Epinephrine, Adrenaline||Adrenal glands||Bodily functions during stressful and emotional states|
|Androgens||Testes (and ovaries and adrenal glands to a lesser extent)||Male secondary sex characteristics, sexual arousal in males and females|
|Estrogens||Ovaries (and testes and adrenal glands to a lesser extent)||Breast development and menarche in females|
|Progesterone||Ovaries (and testes and adrenal glands to a lesser extent)||Preparation of uterus for implantation of fertilized egg|