ENDOCRINE SYSTEM

Endocrine Glands A gland is any organ that produces a secretion. Endocrine glands are groups of tissues which produce hormones from materials already present in the blood or lymph. Hormones act as chemical messengers. They coordinate and direct activities of target cells and organs throughout the body.

HORMONAL CONTROL Occurs through Negative Feedback a drop in the level of a hormone triggers a chain reaction that causes an increase hormones in the blood This feedback mechanism continues until the correct level of hormone is found present in the blood.

PITUITARY GLAND Divided into anterior and posterior lobes Known as the master gland because of its major influence in body’s activities

Anterior Pituitary Lobe Growth Hormone (GH) Is responsible for growth and development of bones and muscles. Also helps fat to be used for energy (this preserves glucose levels)

Anterior Pituitary Lobe Prolactin hormone (PRL) Develops breast tissue and stimulates the production of milk after childbirth. The function in males is unknown.

Anterior Pituitary Lobe Tropic Hormones Thyroid stimulating hormone (TSH) Stimulates the growth and secretion of the thyroid gland. Adrenocorticotropic hormone (ACTH) Stimulates growth and secretion of the adrenal gland.

Posterior Pituitary Lobe Stores 2 hormones produced by the hypothalamus: 1. Oxytocin Released during childbirth. Causes strong contractions of the uterus.

2. Vasopressin Changes into antidiuretic hormone (ADH) when it enters the bloodstream. Maintains a water balance by increasing the amount of water that is absorbed by the kidneys. Results in decreased urine output and increased blood volume.

THYROID GLAND Secretes 3 hormones: Triiodothyronine (T3) Thyroxin (T4) Calcitonin These hormones are produced when thyroid stimulating hormone triggers the thyroid to become active.

Triiodothyronine and Thyroxine The first 2 hormones require iodine to work properly. The iodine for these hormones comes from the diet it combines with the AA tyrosine to form T3 and T4 T 3 and T4 control the rate of cellular metabolism throughout the body.

Calcitonin Controls the calcium ion concentration in the bloodstream. High levels of calcium ions in the blood stimulate the release of calcitonin. Ca+ is then stored in bones and calcium concentrations in the blood stream decreases.

PARATHYROID GLANDS Secrete a hormone called parathormone (PTH)

Parathormone Extracts Ca+ from bones to correct low blood calcium levels. The hormone causes an increase in number and size of osteoclasts (bone- demineralizing cells) which remove calcium from bones.

THYMUS GLAND The thymus secretes a hormone called thymosin. Thymosin Stimulates the lymphoid cells which are responsible for the production of Tcells an important part of the immune system.

Epinephrine (adrenalin) Released in response to stress Epinephrine (adrenalin) Released in response to stress. Increases the heart rate and helps the liver release glucose for energy needs. Considered the “fight or flight” hormone

GONADS – sex organs Ovaries – the female sex organs. Found at the end of each Fallopian tube; produces: estrogen for female characteristics and progesterone which prepares the uterus for implantation.

Testes - male sex organ; found in the scrotum sac; produces: Testosterone for male characteristics.

PANCREAS Pancreas as an endocrine gland produces: 1. insulin - a hormone that promotes the uptake of glucose by cells 2. glucagon - a hormone that causes the liver to breakdown stored glycogen and release it as glucose into the bloodstream

PINEAL GLAND Produces the hormone melatonin

Melatonin Amount of light entering the eye affects the amount of melatonin secreted The darker it is, the more melatonin produced. The lighter it is, the less melatonin produced. Causes low body temperature & sleepiness.

Endocrine Gland Disorders

DISORDERS OF THE ENDOCRINE SYSTEM Endocrine gland disturbances may be caused by: Disease Infection Hyperactivity Hypoactivity

PITUITARY DISORDERS Hyposecretion of growth hormone during childhood will result in: Pituitary Dwarfism = body proportions are normal, but the person has max height of 4’. 2’ 5” < 2’

PITUITARY DISORDERS Hypersecretion of growth hormone during childhood, prior to the ossification of the epiphyseal growth plates, will result in: Gigantism = body proportions are normal, but the person reaches a height of 8 to 9 feet.

8’ 11.5” 8’ 1.5”

PITUITARY DISORDERS Hypersecretion of GH after the long bones have finished growing will result in: Acromegaly = the facial bones (lower jaw and ridge of brow), hands and feet enlarged tremendously.

7’2” 7’7”

THYROID DISORDERS Hyposecretion of the thyroxine due to a lack of iodine in diet. The thyroid works overtime to try to make T3 and T4 hormones. Results in: Hypothyroidism = is evidenced by the presence of a goiter.

THYROID DISORDERS Hypersecretion of thyroxine (usually results from a tumor on the thyroid gland); results in: Hyperthyroidism also known as Grave’s disease. Evidenced by rapid heartbeat, nervous or agitated behavior, and bulging eyes.

Exopthalmos = bulging eyes

THYROID DISORDERS Hyposecretion of thyroxine during childhood. Would be due to a lack TSH; results in: Cretinism = a type of dwarfism where the body retains childlike proportions (the upper body is larger than the lower body). Often results in mental retardation.

PARATHYROID DISORDERS Hyposecretion of parathormone: Low levels of calcium affects the nerves and cause uncontrollable muscle spasms known as tetany.

Hypersecretion of parathormone: Calcium is taken from the bones in excess, weakening the bones. Calcium is deposited in the kidneys resulting in kidney stones Kidney stones in the kidney in the ureter

PANCREATIC DISORDERS The decreased secretion of insulin or the ineffective use of insulin by cells. Diabetes mellitus = results in high blood glucose levels.