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.

FUNCTION OF THE ENDOCRINE SYSTEM Hormones act as chemical messengers. They coordinate and direct activities of target cells and organs throughout the body. Major glands of endocrine system pituitary - thyroid - thymus pineal - parathyroid - adrenals pancreas - gonads

FUNCTION OF THE ENDOCRINE SYSTEM

HORMONAL CONTROL Remember Negative feedback occurs when there is a drop in the level of a hormone triggers a chain reaction of responses to increase hormones in the blood This feedback mechanism continues until the correct level of hormone is found present in the blood.

Endocrine gland disturbances may be caused by: Disease Infection Hyperactivity Hypoactivity

PITUITARY GLAND Located at the base of the brain and connected to the hypothalamus Divided into anterior and posterior lobes Known as the master gland because of its major influence in body’s activities

Hormones of the Anterior Lobe The anterior pituitary lobe is larger of the two lobes; it produces seven hormones: Growth hormone Thyroid stimulating hormone Prolactin hormone Adrenocorticotropic hormone Follicle stimulating hormone Interstitial cell-stimulating hormone Luteinizing hormone

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)

Prolactin hormone (PRL) Develops breast tissue and stimulates the production of milk after childbirth. The function in males is not known.

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.

Follicle-stimulating hormone (FSH) Stimulates the development of eggs in females. Stimulates the production of sperm in males.

Hormones of the Pituitary Gland The posterior pituitary lobe: Stores hormones produced by the hypothalamus: vasopressin oxytocin

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 urinary output and increased blood volume.

Oxytocin Released during childbirth. Causes strong contractions of the uterus.

THYROID GLAND Located in the lower portion of the anterior neck; just below the “Adam’s apple”. Secretes 3 hormones: Triiodothyronine (T3) Thyroxine (T4) Calcitonin

Remember TSH? These hormones are produced when thyroid stimulating hormone triggers the thyroid to become active.

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 controls 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 bloodstream decreases.

PARATHYROID GLANDS Four glands attached to posterior surface of the thyroid Secrete parathormone (PTH)

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

THYMUS GLAND Is located deep to the sternum. The thymus secretes a large number of hormones; the major one is thymosin.

Thymosin Stimulates the lymphoid cells which are responsible for the production of Tcells an important part of the immune system.

ADRENAL GLANDS There are two adrenal glands one is located on top of each kidney. The hormones of the adrenal glands are known as corticoids.

1. Mineralocorticoids – (aldosterone): causes Na+ and water to be absorbed into the bloodstream and increases blood pressure.

2. Glucocorticoids (cortisone and cortisol) – main job is to increase the amount of glucose in the bloodstream. step 1: Converts proteins and fats in the liver into glycogen. step 2: Breaks down glycogen into glucose as needed.

3. Epinephrine (adrenalin) Released in response to stress 3. 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 – in females, 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 Located posterior to the stomach 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 Located posterior to the diencephalon 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.

PITUITARY DISORDERS Hyposecretion of ADH (made from vasopressin) leads to: Excessive urine output called diabetes insipidus. People with this problem are continually thirsty and drink huge amounts of water.

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

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.

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

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. The calcium is deposited in the kidneys resulting in kidney stones

Kidney stones

ADRENAL DISORDERS Hyposecretion of the adrenal cortex due to adrenal insufficiency or to a lack of ACTH from the pituitary gland. Addison’s disease = skin appears “bronzed”, muscle weakness, and weight loss.

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