H ORMONES

W HAT IS A H ORMONE A hormone is a chemical substance released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism.

T HE E NDOCRINE S YSTEM I NTRODUCTION The endocrine system is made up of glands that produce and secrete hormones. These hormones regulate the body's growth, metabolism (the physical and chemical processes of the body), and sexual development and function.metabolism The hormones are released into the bloodstream and may affect one or several organs throughout the body.

T HE E NDOCRINE S YSTEM I NTRODUCTION The major glands of the endocrine system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, and the reproductive organs (ovaries and testes). The pancreas is also a part of this system; it has a role in hormone production as well as in digestion. The endocrine system is regulated by feedback.

H YPOTHALAMUS The hypothalamus is located in the lower central part of the brain.brain This part of the brain is important in regulation of satiety, metabolism, and body temperature. In addition, it secretes hormones that stimulate or suppress the release of hormones in the pituitary gland.

2- P ITUITARY G LAND The pituitary gland is located at the base of the brain beneath the hypothalamus and is no larger than a pea. It is often considered the most important part of the endocrine system because it produces hormones that control many functions of other endocrine glands. When the pituitary gland does not produce one or more of its hormones or not enough of them, it is called hypopituitarism. The pituitary gland is divided into two parts: the anterior lobe and the posterior lobe.

The anterior lobe produces the following hormones, which are regulated by the hypothalamus: 1. Growth hormone - Stimulates growth of bone and tissue (growth hormone deficiency in children results in growth failure. Growth hormone deficiency in adults results in problems in maintaining proper amounts of body fat and muscle and bone mass.) 2. Thyroid-stimulating hormone (TSH) - Stimulates the thyroid gland to produce thyroid hormones (A lack of thyroid hormones either is called hypothyroidism.)

3. Adrenocorticotropin hormone (ACTH) - Stimulates the adrenal gland to produce several related steroid hormones. 4. Luteinizing hormone (LH) and follicle- stimulating hormone (FSH) - Hormones that control sexual function and production of the sex steroids, estrogen and progesterone in females or testosterone in males. 5. Prolactin 5. Prolactin - Hormone that stimulates milk production in females.

T HE POSTERIOR LOBE PRODUCES THE FOLLOWING HORMONES, WHICH ARE NOT REGULATED BY THE HYPOTHALAMUS : 1. Antidiuretic hormone (vasopressin) - Controls water loss by the kidneys. Antidiuretic hormonevasopressin 2. Oxytocin - Contracts the uterus during childbirth and stimulates milk production. Oxytocin

3- T HYROID G LAND The thyroid gland is located in the lower front part of the neck. 90% T 4 and 10% T 3 Affect growth and maturation of tissues, cell metabolism, heat production, oxygen consumption, also plays a role in bone growth and development of the brain and nervous system in children, also help maintain normal blood pressure, heart rate, digestion, muscle tone, and reproductive functions.

4- P ARATHYROID G LANDS The parathyroid glands are two pairs of small glands embedded in the surface of the thyroid gland, one pair on each side. They release parathyroid hormone, which plays a role in regulating calcium levels in the blood and bone metabolism.parathyroid hormone

5- A DRENAL G LANDS The adrenal glands are triangular-shaped glands located on top of each kidney. The adrenal glands are made up of two parts. The outer part is called the adrenal cortex, and the inner part is called the adrenal medulla. The outer part produces hormones called corticosteroids, which regulate the body's metabolism, the balance of salt and water in the body, the immune system, and sexual function. The inner part, produces hormones called catecholamines (for example, adrenaline). These hormones help the body cope with physical and emotional stress by increasing the heart rate and blood pressure.

6- P INEAL B ODY The pineal body, or pineal gland, is located in the middle of the brain. It secretes a hormone called melatonin, which may help regulate the wake-sleep cycle of the body.

7- R EPRODUCTIVE G LANDS The reproductive glands are the main source of sex hormones. In males, the testes, located in the scrotum, secrete hormones called androgens; the most important of which is testosterone. In females, the ovaries, located on both sides of the uterus, produce estrogen and progesterone as well as eggs.

8- P ANCREAS The pancreas is an elongated organ located toward the back of the abdomen behind the stomach.organ abdomenstomach The pancreas has digestive and hormonal functions. One part of the pancreas, the exocrine pancreas, secretes digestive enzymes. The other part of the pancreas, the endocrine pancreas, secretes hormones called insulin and glucagon. These hormones regulate the level of glucose (sugar) in the blood. glucose Alpha—glucagon Beta—insulin

E NDOCRINE D ISORDERS

A CROMEGALY An enlargement of the bones of the hands, feet, and jaws Is a syndrome that results when the pituitary gland produces excess growth hormone.

Condition resulting from a congenital deficiency of thyroid secretion or hypothyroidism Cretinism

From an acquired or inherited decrease in the antidiuretic hormone secreted by the pituitary Diabetes insipidus

Diabetes mellitus A disorder of carbohydrate, fat, and protein metabolism resulting from insufficient insulin production by the pancreas Dwarfism Results from hypo secretion of the growth hormone of the pituitary gland, which has been caused by a tumor, infection, genetic factors, or trauma Gigantism An excessive growth of the long bones caused by hyper secretion of the somatotropic hormone ( pituitary gland )

Graves’ disease Is an autoimmune disease where the thyroid is overactive (hyperthyroidism), producing an excessive amount of thyroid hormones Hyperparathyroidism Causes hypercalcemia, an increased calcium blood level Hypoparathyroidism A decreased secretion of parathyroid hormone that causes tetany Hypoglycemia Results from increased insulin production by the pancreas

Hypothyroidism Also called Hashimoto's disease, results from an insufficient production of thyroxine Virilism Results from increased secretion in the adrenal glands. The presence of male secondary sexual characteristics in a female.