Nx Endocrine

GOOD AFTERNOON

ENDOCRINE SYSTEM BY : Jeanette C. Sy, MD

For the body to function normally, homeostasis is very important. HOMEOSTASIS depends upon the precise regulation of the organs and the organ systems of the body. The NERVOUS and ENDOCRINE SYSTEMS are the two major systems responsible for that regulation

Nervous and Endocrine System - Together they regulate and coordinate the activity of nearly all other body structures - When these systems fail to function properly homeostasis is not maintained - Any malfunction of either system results to diseases

REGULATORY FUNCTIONS NERVOUS 1. Controls the activity of tissues by sending action potentials along axons, which release chemical signals at their ends

ENDOCRINE 1. Releases chemical signals into the circulatory system, which carries them to all parts of the body

NERVOUS

ENDOCRINE

2. Acts more quickly

2. Acts more slowly

3. Short-term effects

3. Longer lasting effects

4. Controls a specific tissue or organ

4. Stimulates several tissues or organs

FUNCTIONS OF THE ENDOCRINE SYSTEM The main regulatory function of the endocrine system include : 3. Water balance - By controlling the solute concentration of the blood

2. Uterine contractions and milk release - Regulates uterine contractions during delivery of newborn - Stimulates milk release from the breasts in lactating females 3. Ion regulation - Regulates Na+, K+, and Ca 2+ concentrations in the blood

4. Growth, metabolism and tissue maturation - Regulates growth of many tissues such as bone and muscle, and the rate of metabolism of many tissues (Maintain a normal body temp and mental functions) - Maturation of tissues, which result in the development of adult features and behaviors

5. Heart rate and BP regulation - Ex. Epinephrine and norepinephrine 4. Blood glucose control - Ex. Insulin and glucagon 7. Immune system regulation - Helps control the production and functions of the immune system

2. Reproductive functions control - Controls the development and the functions of the reproductive systems in males and females

CHEMICAL SIGNALS - Are molecules released from one location that move to another location to produce as response - Types : 1. Intracellular chemical signals - produced in one part of the cell and act on another part of the SAME cell

2. Intercellular chemical signals - released from one cell, are carried in the intercellular fluid and brought to ANOTHER cell

Functional Classification of Intercellular Chemical Signals 1. AUTOCRINE - Secreted by cells in a local area and influence the activity of the SAME CELL TYPE from which it was secreted - Ex. Eicosanoids (prostaglandins, thromboxanes, prostacyclins, leukotrienes)

2. PARACRINE - Secreted into tissue spaces - usually has a localized effect on other tissues - Ex. Histamine

3. HORMONE - Secreted into the blood - Travels some distance to target tissues - Influences specific activities - Ex. Thyroid hormones, GH, insulin, epinephrine, estrogen, progesterone, testosterone

1. NEUROHORMONE - Produced by neurons and functions like hormones - Ex. Oxytocin, ADH

1. NEUROTRANSMITTER - Or Neuromodulator - Produced by neurons and secreted into extracellular spaces by presynaptic nerve terminals and influences postsynaptic cells

1. PHEROMONE - Are chemicals emitted by living organisms to send messages to individuals of the same species - Modifies physiology and behavior of individuals - Have direct effects on sexual habits - “Aphrodisiacs” or “Secret seducers”

RECEPTORS - Are proteins or glycoproteins - Chemical signals bind to receptors to produce a response - RECEPTOR SITE is the portion of the receptor where a chemical signal binds - Only a specific type of chemical binds to a specific type of receptor = SPECIFICITY

TYPES OF RECEPTOR 1. 3. -

MEMBRANE-BOUND RECEPTORS located in the cell membrane INTRACELLULAR RECEPTORS Located in either the cytoplasm or nucleus of the cell

MEMBRANE-BOUND RECEPTOR RESPONSES 1. Receptors that directly alter membrane permeability 2. Receptors and G proteins (GTP) - open and close membrane channels to produce a response - activate enzymes that produce intracellular chemical signals

3. Receptors that directly alter the activity of enzymes

HORMONES - Endocrine derived from the Greek words endo and krino meaning “within” and “to separate” - are produced within and secreted from endocrine glands but have effects at locations that are away from the glands that secret them - Ex. Thyroid and Adrenal Glands

Exocrine glands - Secrete their products into ducts which exit the glands and carry the secretory products to an external or internal surface such as the skin or digestive tract - Ex. Sweat and the Salivary glands

ENDOCRINE SYSTEM - Consists of the endocrine glands of the body - HORMONES are the intercellular chemical signals secreted by the endocrine glands - NEUROHORMONES are hormones secreted from cells of the nervous system

HORMONES - are distributed in the blood to all parts of the body, but only certain tissues called “target tissues” respond to each type of hormone - Chemical categories : a. Protein derivatives ex. Hormones of anterior pituitary gland

b. Lipid derivatives - 1. Eicosanoids (derived from the fatty acid arachidonic acid) includes : PG, thromboxanes, prostacyclins, leukotrienes

1. Sex steroids - a. Estrogen = fr adrenal cortex & gonads = affect function and maturation of female secondary sex organs (female sexual determination) - b. Progestins = fr ovaries and placenta = mediate menstruation and maintain pregnancy

c. Androgens = or testosterone = fr adrenal cortex & gonads = affects male secondary sex organs (male sexual determination) 3. Mineralocorticoid = aldosterone 4. Glucocorticoid = cortisol

REGULATION OF HORMONE SECRETION - Controlled by : NEGATIVE-FEEDBACK MECHANISMS

Regulation of…………. cont 3 Ways of Hormone secretion regulation 1. Blood levels of chemicals ex. Insulin secretion is controlled by blood glucose levels

3 Ways……….cont. 3. Hormones - Secretion of some hormones is controlled by other hormones - Ex. Pituitary gland hormones acts on ovaries and testes, causing those organs to secrete sex hormones

3 Ways………….cont. 3. Nervous System - Secretion of some hormones is controlled by the nervous system - Ex. Epinephrine is released from the adrenal medulla as a result of nervous system stimulation

ENDOCRINE GLANDS AND THEIR HORMONES

REMEMBER : Endocrine system consists of ductless glands, which secrete hormones directly into the circulatory system

PITUITARY AND HYPOTHALAMUS - Pituitary gland or hypophysis is a small gland about the size of a pea Divided into 2 parts: a. anterior pituitary b. posterior pituitary - Hypothalamus is an important autonomic nervous system and endocrine control center of the brain

- The secretion of hormones from the anterior pituitary is controlled by RELEASING HORMONES, which are produced by the nerve cells of the hypothalamus - Releasing hormones either stimulates or inhibits release of pituitary hormones - Are transported through the capillary beds and veins called “HYPOTHALAMIC-PITUITARY PORTAL” SYSTEM

HYPOTHALAMUS Releasing hormones (hypo-pit portal system) PITUITARY GLAND Hormones (circulatory system) TARGET TISSUES (response)

HORMONES OF THE ANTERIOR PITUITARY GLAND 1. 2. 3. 4. 5. 6. 7.

Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Prolactin Melanocyte-stimulating hormone (MSH)

HORMONES OF THE ANTERIOR PITUITARY 1. GROWTH HORMONE - Stimulates growth of bones, muscles and other organs by increasing protein synthesis - Def: due to abn development of pituitary Pituitary dwarf (small & proportioned) - Excess : due to hormone secreting tumors Gigantism (abnormally tall)

REMEMBER : If excess hormone is secreted after growth in bone length is complete, growth in diameter but not in length continues, as a result facial features and hands become large

ACROMEGALY

SOMATOMEDINS - A group of protein chemical signals that partly influence the effect of GH - GH increases somatomedin secretion from tissues such as liver - Somatomedins bind to receptors on cells of tissues such as bone and cartilage and stimulate growth

HORMONES OF THE ANTERIOR PITUITARY GLAND • • • • • • •

Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Prolactin Melanocyte-stimulating hormone (MSH)

2. THYROID-STIMULATING HORMONE - Binds to thyroid gland cell receptors and cause the cells to produce Thyroid Hormone - TSH secretion is regulated by Thyroid Releasing Hormones (TRH) from the hypothalamus

- Too much TSH causes the thyroid gland to enlarge and secrete too much thyroid hormone - Too little TSH causes the thyroid gland to decrease in size and too little thyroid hormone is secreted

THYROID GLAND - Made up of 2 lobes connected by a narrow band called the ISTHMUS - Lobes are located on either side of the trachea, inferior to the larynx - One of the largest endocrine glands - Contains numerous THYROID FOLLICLES - PARAFOLLICULAR CELLS are the connective tissues that surrounds the follicles

THYROID ……..cont. - Cells of the thyroid follicles synthesize THYROID HORMONES which are stored in the follicles - Main function of thyroid gland is to secrete THYROID HORMONES, which regulate the rate of metabolism in the body

THYROID HORMONES 1. THYROXINE / TETRAIODOTHYRONINE - Contains 4 iodine atoms (T4) 2. TRIIODOTHYRONINE - Contains 3 iodine atoms (T3)

Thyroid gland requires IODINE to synthesize hormones Iodine is taken by the thyroid follicles in which hormone synthesis occurs Thyroid hormones are stored in combination with a protein called THYROGLOBULIN within the thyroid follicles

REMEMBER : If the quantity of iodine present is not sufficient, the production and secretion of the thyroid hormones decrease

Thyroid hormone secretion is regulated by TSH from the anterior pituitary gland. INC TSH = INC T3 / T4 synthesis DEC TSH = DEC T3 / T4 synthesis Regulated by negative feedback system

Low blood T3/T4

High blood T3/T4

Stimulates Hypothalamus Inc TSH releasing hormone

Dec TSH-Releasing Hormone

Inc TSH fr Ant Pituitary

Dec TSH from Ant Pituitary

Inc T3/T4 synthesis

Dec T3/T4 synthesis

When T3/T4 secretion is reduced below normal, TSH releasing hormone from hypothalamus and TSH from anterior pituitary increases substantially. Excess TSH causes the thyroid gland to enlarge, a condition called a GOITER

IODINE DEFICIENCY GOITERS - Develops if the iodine in the diet is too low. Less T3/T4 is synthesized. - TSH-releasing hormone and TSH increases above normal levels and cause dramatic enlargement of the thyroid gland.

A deficiency of iodine is not as common as it used to be. There are table salt with iodine (IODIZED SALT) added to it that are available nowadays.

RA 8172 An Act Promoting Salt Iodization Nationwide and for related purposes and ASIN Law providing the use of iodine in the food for healthy citizenry.

REMEMBER : Growth and development cannot proceed normally without a normal rate of thyroid hormone secretion.

HYPOTHYROIDISM - Lack of thyroid hormones - In infants, hypothyroidism can result in CRETINISM (a person is mentally retarded has a short stature with abnormally formed skeletal structures)

- In adults, it results in reduced rate of metabolism, sluggishness and a reduced ability to perform routine tasks and MYXEDEMA (accumulation of fluid and other molecules in the SQ tissue)

HYPERTHYROIDISM - Elevated rate of thyroid hormone secretion - Results in elevated rate of metabolism, extreme nervousness and chronic fatigue

GRAVE’S DISEASE - A type of hyperthyroidism resulting from the production of abnormal proteins by the immune system that are similar in structure and function to TSH - Often accompanied by bulging of the eyes known as “EXOPHTHALMIA”

In GRAVE’S DISEASE, the immune system produces a large amount of protein that is so much like TSH that it binds to cells of the thyroid gland and acts like TSH. Unlike TSH, the secretion of this protein does not respond to negative feedback system.

CALCITONIN - Secreted by parafollicular cells - It is secreted if the blood concentration of Ca2+ becomes too high - Inhibits bone resorption of Ca2+ by inhibiting osteoclasts

PARATHYROID GLANDS - FOUR tiny glands are embedded in the posterior wall of the thyroid gland - Secrete PARATHYROID HORMONE (PTH) for blood Ca2+ regulation - More important that Calcitonin in Ca2+ regulation - PTH acts to raise blood Ca2+ levels to normal

PTH Calcium Regulation 1. Increases the absorption of Ca2+ from the intestine by causing an increase in active Vit D formation 2. Increases resorption (breakdown) of bone tissue to release Ca2+ into the circulatory system 3. Decreases the rate at which Ca2+ are lost in the urine

VITAMIN D - Increases absorption of Ca2+ and raises blood Ca2+ levels. - It is produced from precursors in the skin that are modified by the liver and kidneys - UV light acting on the skin is required for the 1st stage of Vit D synthesis - Can also be supplied in the diet

REMEMBER : Prolonged bone resorption (breakdown) due to decrease blood Ca2+ level results in reduced bone density. Reduced bone density causes soft, flexible bones that are easily deformed in young people and are porous, fragile bones in older people

HYPERPARATHYROIDISM - Abnormally high PTH (high Ca2+) - Can result from a tumor of parathyroid gland - Bones become soft and easily fractured - Excess Ca2+ = kidney stones - Ms and nerves become less excitable resulting to fatigue and weakness

HYPOPARATHYROIDISM - Abnormally low PTH (low Ca2+) - Can result from injury or surgical removal of the thyroid and parathyroid glands - Dec rate of bone resorption - reduced vit D formation - Ms and nerves become excitable resulting to frequent cramps and tetanus - TETANUS can affect respiratory ms = Death

HORMONES OF THE ANTERIOR PITUITARY GLAND • • • • • • •

Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Prolactin Melanocyte-stimulating hormone (MSH)

3. ADRENOCORTICOTROPIC HORMONE - Binds to the receptors on cells in the adrenal gland cortex - Increases secretion of CORTISOL (Hydrocortisone) from adrenal gland - ACTH secretion is regulated by CORTICOTROPIC RELEASING HORMONE from the hypothalamus

ADRENAL GLANDS - Known also as “SUPRARENAL GLANDS” - Are 2 small glands located superior to each kidney - 2 Parts : 1. Adrenal medulla – marrow or middle 2. Adrenal cortex – bark or outer - Adrenal medulla and cortex function separately

ADRENAL MEDULLA - Principal hormone released is EPINEPHRINE or ADRENALIN and small amounts of NOREPINEPHRINE - EPI and NE are released in response to stimulation by the SYMPATHETIC NERVOUS SYSTEM - Referred as “fight-or-flight” hormones coz of their role in preparing the body for vigorous physical activity

MAJOR EFFECTS OF EPINEPHRINE AND NE 1. Increases breakdown of glycogen to glucose in the liver, the release of glucose into the blood and the release of FA from fat cells (Glucose and fatty acids are used as energy sources to maintain the body’s increased rate of metabolism)

2. Increase in heart rate, which causes BP to increase 3. Stimulation of smooth muscle in the walls of arteries supplying the internal organs and the skin, but not those supplying skeletal muscle.

4. Increase in BP because of smooth muscle contraction in the walls of blood vessels in the internal organs and the skin 5. Increase in the metabolic rate of several tissues, esp skeletal muscle, cardiac muscle and nervous tissue

PHEOCHROMOCYTOMA - A benign tumor of the adrenal medulla - Symptoms result from the release of the large amounts of epinephrine and NE from the tumor - Sx : HPN, sweating, nervousness, pallor and tachycardia - HPN increases the chance of heart attack and stroke

ADRENAL CORTEX - 3 Classes of Steroid Hormones secreted : 1. GLUCOCORTICOIDS - help regulate blood nutrient levels in the body a.CORTISOL = major glucocorticoid b.CORTISONE = closely related to cortisol

CORTISOL - Inc the breakdown of protein and fat and inc their conversion to source of energy - During STRESS, it aids the body in responding to stressful situations by providing energy sources for the tissues - Reduces inflammatory response

CORTISONE - A drug similar to cortisol - Is sometimes given to people who have severe allergies or extensive inflammation, or to people who suffer autoimmune dses

3 Classes Steroid Hormones………cont. 2. MINERALOCORTICOIDS - Help regulate blood volume and blood levels of K+ and Na+ a. ALDOSTERONE - major hormone of this class - binds to receptors in the kidney, intestine, sweat glands and salivary glands

ALDOSTERONE - Causes Na+ and H2O to be retained in the body - Increases rate of K+ elimination - Secretion affected by : a. directly – serum Na+ and K+ (K+ > Na+) b. indirectly – RENIN secretion

Low BP

RENIN ( fr kidneys)

ANGIOTENSINOGEN

ANGIOTENSIN I Angiotensin-converting enzyme (ACE)

ANGIOTENSIN II Smooth ms in BV to constrict ( BP)

Acts on Adrenal Cortex to inc ALDOSTERONE

3 Classes Steroid Hormones………..cont. 3. ANDROGENS - ability to stimulate the development of male sexual characteristics - Males : most are secreted by testes - Females : it influence the female sex drive

HORMONES OF THE ANTERIOR PITUITARY GLAND • • • • • • •

Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Prolactin Melanocyte-stimulating hormone (MSH)

1. GONADOTROPINS - Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH) - Binds to receptors on the cells of the gonads (ovaries and testes) - Regulate the growth, development and functions of the gonads - LH and FSH secretion is regulated by GONADOTROPIN RELEASING HORMONE from the hypothalamus

LH - IN FEMALES : Causes the ovulation of oocytes and the secretion of sex hormones ESTROGEN and PROGESTERONE from the ovaries - IN MALES : referred as INTERSTITIAL CELLSTIMULATING HORMONE (ICSH) Stimulates interstitial cells of the testes to secrete TESTOSTERONE

FSH - Stimulates the development of follicles in the ovaries and sperm cells in the testes

REMEMBER :

Without LH and FSH, the ovaries and sperm cells in the testes decrease in size, no longer produce oocytes and sperm cells, and no longer secrete hormones

TESTES AND OVARIES - Secretes hormones in addition to producing sperm cells and oocytes - Hormones produced are important in the development of the sexual characteristics

IN MALES : TESTOSTERONE - Main sex hormone in males - Responsible for growth and development of the ff : a. male reproductive structures b. muscle enlargement c. growth of body hair d. voice changes e. male sexual drive

IN FEMALES : 2 MAIN CLASSES OF SEX HORMONES ESTROGEN and PROGESTERONE - Secretion is regulated by FSH and LH - Both contribute to the development and function of the female characteristics a. breast enlargement b. fat distribution c. regulate female menstrual cycle

HORMONES OF THE ANTERIOR PITUITARY GLAND • • • • • • •

Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Prolactin Melanocyte-stimulating hormone (MSH)

5. PROLACTIN - Binds to receptors in the cells of the breast and helps promote development of the breast and milk production during pregnancy - 2 releasing hormones regulate prolactin secretion (one inc and one dec secretion)

HORMONES OF THE ANTERIOR PITUITARY GLAND • • • • • • •

Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Prolactin Melanocyte-stimulating hormone (MSH)

6. MELANOCYTE-STIMULATING HORMONE - Binds to receptors on melanocytes and causes them to synthesize MELANIN - Overproduction of melanin = skin darkening - 2 releasing hormones regulate MSH secretion (one inc and one dec MSH prod)

REMEMBER : The structure of ACTH and MSH are similar. Both hormones causes skin to darken.

HORMONES OF THE POSTERIOR PITUITARY GLAND 1. ANTIDIURETIC HORMONE (ADH) 2. OXYTOCIN

POST PIT HORMONES…….cont. 1. ANTIDIURETIC HORMONE - Also known as VASOPRESSIN - Binds to receptors and increases water reabsorption by kidney tubules - Result : Less water lost as urine - INC ADH : concentrated urine - DEC ADH : dilute urine

DIABETES INSIPIDUS (DI) - Lack of ADH or vasopressin - Results to : 1. large volume of urine output 2. inc osmolality of the body fluids and the loss of important electrolytes (Na+, K+, Ca2+) in the urine - 2 Types : 1. Central DI 2. Nephrogenic DI

CENTRAL DI - Is caused by damage of hypothalamus or pituitary gland as a result of infection, head injury, surgery or tumor - More common

NEPRHOGENIC DI - Occurs as a result of defect in parts of the kidneys that reabsorb water back into the bloodstream - Less common - Kidney problems can be due to : drug toxicity (amphothericin B, lithium) kidney disease (polycystic kidney dse)

POST PIT HORMONES…….cont. 2. OXYTOCIN - causes contraction of the smooth muscle cells of the uterus and milk ejection, or milk “let-down” from the breasts in lactating mother

DIFFERENT ENDOCRINE GLANDS • • • • • • •

Pineal body Pituitary gland Thyroid gland Thymus gland Adrenal gland Pancreas Gonads

PINEAL BODY - Is a small pinecone-shaped structure located superior and posterior to the thalamus of the brain - Produces MELATONIN - Melatonin acts to inhibit the functions of the reproductive system by decreasing LH and FSH

thalam us

THYMUS GLAND - pink-gray organ in the upper part of the mediastinum behind the sternum - Lymphocytes are processed into T-lymphocytes which is responsible for cellular immunity - Help cells to recognize and destroy invading bacteria, viruses, abnormal cell growth like cancer cells

PANCREAS - 2 PARTS : a. exocrine – secretes digestive enzymes b. endocrine – secretes hormones - made up of islets of Langerhans - Islets : Alpha cells – glucagon Beta cells - insulin

REMEMBER : It is important to maintain blood glucose levels within a normal range of values. A decline in the blood glucose level can cause the nervous system to malfunction because GLUCOSE is the main source of energy

When blood glucose decreases, fats and proteins are broken down rapidly to provide as alternative source of energy Fatty acids are converted to KETONES by the liver and are released into the circulation. Fatty acids and Ketones can cause ph to decrease causing ACIDOSIS.

If blood glucose is too high, the kidneys produce large volumes of urine output containing substantial amounts of GLUCOSE. Rapid loss of water in the form of urine results to DEHYDRATION.

INSULIN - Released fr beta cells in response to high blood glucose - Stimulated also by increased amino acids - Major target tissues : liver, adipose tissue, muscles and the area of hypothalamus that controls the appetite, called the “SATIETY CENTER”

INSULIN………..cont. - Insulin binds to receptors and cause : Inc rate of glucose and amino acid uptake in these tissues Glucose is converted to glycogen and fat Amino acids are used to synthesize protein

DIABETES MELLITUS - Result from : a. too little insulin secretion fr pancreas b. insufficient numbers of insulin receptors on target cells c. defective receptors

In DM, tissues cannot take up glucose effectively, blood glucose levels become very high “HYPERGLYCEMIA” Excess glucose in the blood is excreted in the urine. Thus urine volume becomes very high “POLYURIA” Results to dehydration and excessive thirst “POLYDIPSIA”

Despite high blood glucose, fats and proteins are broken down to provide energy source for metabolism. “POLYPHAGIA” Results to wasting of body tissues, acidosis, ketosis and lack of energy

GLUCAGON - Released from the alpha cells when blood glucose is low - Binds to receptors primarily in the liver - Result : conversion of GLYCOGEN stored GLUCOSE

SUMMARY Insulin and Glucagon regulate blood sugar High BG causes inc insulin and dec glucagon Low BG causes dec insulin and inc glucagon Epinephrine and Cortisol - Breakdown of protein and fats - Synthesis of glucose Growth hormone - Slows protein breakdown - Favors fat breakdown

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