The Endocrine System

Anterior pituitary

The anterior pituitary is the anterior lobe of the pituitary gland. The anterior lobe of the pituitary gland makes up 80% of its weight.  The anterior pituitary is essential because it produces and secretes hormones that regulate many physiological processes.  Some of these processes are stress. growth, and reproduction.  The major hormones that are secreted are as follows: adrenocorticotropic hormone, growth hormone, follicle-stimulating hormone, luteinizing hormone, prolactin, and thyroid-stimulating hormone.  adrenocorticotropic hormone targets the adrenal glands and is meant to regulate the secretion of glucocorticoids.  The growth hormone works on the Liver and the adipose tissue, or fat. As its name suggests, the job of the growth hormone is to promote growth.  The follicle-stimulating regulate the growth of the reproduction system.  This hormone targets the ovaries in women and the testes in men.  The luteinizing hormone also targets the ovaries and testes but regulates sex hormone production.  Prolactin's effect is on the secretion of the sex hormones estrogen and progesterone as well as the milk production in women.  Finally, the thyroid-stimulating hormone effects the secretion of thyroid hormones from the thyroid gland.

A disorder of the anterior pituitary is the oversecretion or undersecretion of certain hormones.  Oversecretion of the growth hormone can result in gigantism, a condition distinguished by excessive growth.  Undersecretion of the growth hormone could result in dwarfism which is a condition that is characterized by short stature.

Posterior pituitary
The posterior pituitary is the posterior lobe of the pituitary gland.  Just like the anterior pituitary, the posterior pituitary secretes peptide hormones.  It secretes them into the capillaries of the hypophyseal circulation.  Rather than a gland, the posterior pituitary is a collection of axonal projections.  The two major hormones that the posterior pituitary secretes are oxytocin and vasopressin.  Oxytocin targets the uterus and the mammary glands and regulates uterine contractions and lactation.  Vasopressin works on the kidneys and stimulates water retention and raises blood pressure.  One disorder of the posterior pituitary is undersecretion. This can cause a deficiency of vasopressin and result in central diabetes insipidus.

Hypothalamus
The hypothalamus is located in the brain just under the thalamus.  Some of the things that the hypothalamus regulates are hunger, thirst, body temperature, and circadian cycles.  It uses the pituitary gland to link the nervous and endocrine systems.  The hypothalamus creates and secretes neurohormones.  Neurohormones control the secretion of hormones from the anterior pituitary gland.  One disorder of the hypothalamus is narcolepsy.  Narcolepsy causes one to involuntarily fall asleep at any time.

Thyroid
The thyroid is a small gland located in the front of the neck just below the larynx.  The thyroid converts iodine from food into thyroid hormones.  These hormones are very important because every cell in the body depends on them.  The major hormones that are secreted by the thyroid are thyroxine, triiodothyronine, and calcitonin.  Thyroxine and triiodothyronine serve numerous purposes. Calcitonin helps to regulat calcium levels in the blood.  Toxic multinodular goitre is a disease of the thyroid.  It is caused by hyperthyroidism, or overactivity of the thyroid.  Symptoms may include intolerance to heat, weight loss, increased appetite, tremors, and irritability.

Parathyroid
The parathyroid glands are small glands in the neck.  The hormones secreted by the parathyroid help control calcium and phosphorus hemostasis and also helps in bone physiology.  Hyperparathyroidism is overactivity of the parathyroid glands, this disorder can have serious consequences.  Hyperparathyroidism can lead to hypercalcemia and osteitis fibrosa cystica.  The cure forh yperparathyroidism is the removal of the overactive gland.

Adrenal cortex
The Adrenal cortex is located along the outside of the adrenal gland.  The hormones from the adrenal cortex are made from cholesterol.  These hormones have an effect on the body's metabolism, the chemicals in the blood, and some characteristics of the body.  Some of the hormones secreted by the adrenal cortex are hydrocortisone hormone, corticosterone, and aldosterone hormone.  Hydrocortisone hormones controls the body's use of fats, proteins, and carbohydrates.  Corticosterone suppresses inflammatory reactions in the body and has an effect on the immune system.  Aldosterone hormone controls the level of sodium in urine.  Chronic adrenal insufficiency, or Addison's disease, is a condition in which the body does not produce enough of certain adrenal hormones.  Some signs of Addison's disease are weakness, irritability, nausea, vomiting, and depression.

Adrenal Medulla
The adrenal cortex is located in the center of the adrenal gland.  The adrenal medulla secretes the amino acid tyrosine into the catecholamines adrenaline and noradrenaline.  When someone is faced with a stress such as exercise or imminent danger, medullary cells release adrenaline  into the blood.  This is part of the fight or flight response.  A disorder of the adrenal medulla is pheochromocytomas.  Pheochromocytomas is when a tumor causes the over production of adrenaline and can cause high blood pressure.  This can be deadly if the blood pressure rises too far.

Pancreas
The pancreas is located below the stomach near the liver.  The pancreas produce enzymes that break down food for digestion.  Diabetes mellitus is a disease of the pancreas.  It is caused by high glucose blood sugar.  It requires medical diagnosis, treatment, and lifestyle changes.  Some signs of diabetes mellitus are increased thirst and appetite, weight loss, and fatigue.

Ovary
Ovaries are found only in females.  They are the egg-producing organs and  there are two in normal females.  The two major hormones secreted by the ovaries are activin and inhibin.  Activin is a peptide and plays a role in the regulattion of the menstrual cycle.  Inhibin is closely related and performs the same function.  Polycystic ovary syndrome is a disorder of the ovary caused by excess production of luteinizing hormone.  Symptoms of polycystic ovary syndrome include acne, a deepened voice, a decrease in breast size, and an increase in muscle size and in body hair growing in a male pattern. 

Testes
    Testes are the male generative glands.  The best known hormone secreted by the testes is testosterone, which is a steroid hormone and the primary male hormone.  Luteinizing hormone and follicle-stimulating hormone are also secreted by the testes.  Luteinizing hormone essential for reproduction.  Follicle-stimulating hormone stimulates the growth of immature Graafian follicles to maturity.  Hypogonadism is undersecretion of testosterone.  Symptoms of hypogonadism include erectile dysfunction, infertility, and decrease in muscle mass.

Pineal gland
    The pieneal gland is located near the center of the brain.  The pineal gland secretes melatonin.  Melatonin is found in all living creatures and plays rolls in the sleep-wake cycle, the immune system, and is an antioxidant.  A dysfunctioning pineal gland can have an effect on sleep and activity as well as reproduction.