The adrenal medulla produces epinephrine and norepinephrine, which cause the fight or flight response. The thyroid gland produces triiodothryonine and thyroxine, which are used for metabolism, growth, and development. The ovaries and placenta produce estrogen and progesterone, which are used for fetal/maternal development and egg production. Lastly, the stomach and small intestines produce gastrin and secretin, which are used to assist digestion and nutrient absorption.

The adrenal medulla produces epinephrine and norepinephrine, which cause the fight or flight response. The thyroid gland produces triiodothryonine and thyroxine, which are used for metabolism, growth, and development. The ovaries and placenta produce estrogen and progesterone, which are used for fetal/maternal development and egg production. Lastly, the stomach and small intestines produce gastrin and secretin, which are used to assist digestion and nutrient absorption.

Thyroid hormone is secreted by the thyroid and plays a role in bone growth, neural maturation, and the body's basal metabolic rate. It is released in response to thyroid-stimulating hormone (TSH) from the anterior pituitary, and targets cells throughout the body. Hypothyroidism is characterized by reduced synthesis of thyroid hormones, and can present as weight gain, fatigue, and sensitivity to cold.

Cortisol, a hormone secreted by the adrenal gland, functions to maintain blood pressure by upregulating the number of alpha-1 receptors on arterioles.

Steroids, when taken exogenously, diminish the production of steroids in the body. This can lead to atrophy of the adrenal glands (responsible for producing cortisol-stress steroid hormone). Thus, when patients are taking steroids for whatever reasons (sports, chemo, infection and etc) it is important for the steroids to be tapered off and not removed immediately since the body needs time to begin to reproduce the hormone again.

When thinking of hormones, it helps to remember that they are generally slow acting, indirect, and long lasting. All endocrine hormones travel through the bloodstream in order to reach their target cells. It can help to compare the activity of hormones to the activity of neurotransmitters, which are fast acting and have immediate effects on their target cell. Consider the effects of acetylcholine release at a neuromuscular junction in comparison to growth hormone release into the blood. The muscle twitch is much more transient and quick to react, whereas the effects of growth hormone can take much longer to appear.

Neural or synaptic communication occurs when a neurotransmitter (or chemical messenger) diffuses across the synaptic cleft of the presynaptic neuron and postsynaptic neuron or target cell. Examples of these neurotransmitters include acetylcholine and norepinephrine. Endocrine communication occurs when chemical messengers are released into the blood stream. These chemical messengers are called hormones.

Neural or synaptic communication occurs when a neurotransmitter (or chemical messenger) diffuses across the synaptic cleft of the presynaptic neuron and postsynaptic neuron or target cell. Examples of these neurotransmitters include acetylcholine and norepinephrine. Endocrine communication occurs when chemical messengers are released into the blood stream. These chemical messengers are called hormones.

The liver secretes angiotensinogen and insulin-like growth factors. Only angiotensinogen is responsible for increasing blood pressure by acting on blood vessels. Cortisol is released by the adrenal cortex, oxytocin is released by the posterior pituitary, and vitamin D3 is found being activated in the skin. Angiotensinogen is a zymogen that is converted into angiotensin I by renin (secreted by the kidney). Then angiotensin converting enzyme (ACE) converts angiotensin I into angiotensin II, which is a potent vasoconstrictor. Angiotensin II also promotes the release of aldosterone from the adrenal cortex, which increases sodium reabsorption. Lastly, antidiuretic hormone (ADH) is released from the posterior pituitary to act on the distal convoluted tubule and the collecting duct to increase the permeability of water via upregulation of aquaporins. Together, these hormones act to increase blood pressure.

The liver secretes angiotensinogen and insulin-like growth factors. Only angiotensinogen is responsible for increasing blood pressure by acting on blood vessels. Cortisol is released by the adrenal cortex, oxytocin is released by the posterior pituitary, and vitamin D3 is found being activated in the skin. Angiotensinogen is a zymogen that is converted into angiotensin I by renin (secreted by the kidney). Then angiotensin converting enzyme (ACE) converts angiotensin I into angiotensin II, which is a potent vasoconstrictor. Angiotensin II also promotes the release of aldosterone from the adrenal cortex, which increases sodium reabsorption. Lastly, antidiuretic hormone (ADH) is released from the posterior pituitary to act on the distal convoluted tubule and the collecting duct to increase the permeability of water via upregulation of aquaporins. Together, these hormones act to increase blood pressure.

When thinking of hormones, it helps to remember that they are generally slow acting, indirect, and long lasting. All endocrine hormones travel through the bloodstream in order to reach their target cells. It can help to compare the activity of hormones to the activity of neurotransmitters, which are fast acting and have immediate effects on their target cell. Consider the effects of acetylcholine release at a neuromuscular junction in comparison to growth hormone release into the blood. The muscle twitch is much more transient and quick to react, whereas the effects of growth hormone can take much longer to appear.