Endocrine System

Nestor T. Hilvano, M.D., M.P.H.

Learning Objectives I: Introduction and Pituitary Gland

1. Explain the mechanisms of intercellular communication and give its importance.

2. Compare the 3 structural classes of hormones.3. Discuss the mechanisms of hormonal action and

control of endocrine organs.4. Describe the structure and function of the pituitary

gland including its relations with the hypothalamus.5. Identify the hormones produced by the anterior and

posterior pituitary gland and specify hormonal functions.

6. Discuss the effects of abnormal levels of pituitary hormone production.

Mechanisms of Cell Communications

• Direct communication- across gap junction (pores) in cell membrane allow ions and molecules to move from cell to cell of the same type.

• Synaptic communication- released from neurons to travel across synapse to 2nd cell

• Paracrine communication- secreted into ECF (tissue fluid) to affect nearby cells

• Endocrine communication- chemical messengers that travel in the blood circulation

Endocrine System

• Regulate long term processes for growth, development, and reproduction.

• Uses chemical messengers to relay information called ___________.

• Chemical messengers travel thru the _______ to reach target organs.

a. hormones b. enzymes

c. intersitial fluids d. blood

3 Major Classes of Hormones• Circulate freely or bound to transport proteins1. Amino acid derivatives – biogenic amines a) tyrosine derivatives – TH, Epi, NE, dopamine b) tyrptophan derivatives - melatonin2. Peptide hormones – chains of a.a. a) glycoproteins – TSH, Gonadotrophsb) short polypeptides – ACTH, ADH, GH, MSH3. Lipid derivatives a) eicosanoids – prostaglandin• steroid hormones – estrogen, progesterone,

androgen, aldosterone, glucocorticoid

Mechanisms of Hormonal Action• Hormone interact with Receptor to affect a

target cell. • Hormone receptors are located either on the

plasma membrane or inside the nucleus.• Hydrophilic Hormones: Mode of Action- on

plasma membrane receptor• Hydrophobic Hormones: Mode of Action- on

nucleus receptor

Control of Endocrine Activity: Hypothalamus

1. Secretes regulatory hormones: Releasing, or Inhibitory

2. Acts as an endocrine organ:

a) supraoptic nucleus- produced ADH

b) paraventricular nucleus- produced Oxytocin

3. Control sympathetic output to Adrenal medulla, which secretes catecholamines (epi, nor-epi).

Pituitary Gland

• Also called _________, lodged in sella turcica.

• _____ lobe - consists of pars distalis, pars intermedia, pars tuberalis

• _____ lobe - consists of infundibulum, pars median eminence, neurohypophysis (pars nervosa)

a. Anterior lobe b. Posterior lobe c. Hypophysis d. Hypothalamus

Anterior Lobe of Pituitary Gland

• Anterior lobe of Pituitary gland secretes/releases Tropic hormones = which target other endocrine organs

Include Somatotropin (GH), Prolactin (LTH), Thyrotropin (TSH), Corticotropin (ACTH), Gonadotropin (FSH, LH), Melanotropin (MSH)

• Give the actions (effects/functions) of these hormones.

Posterior Lobe of Pituitary Gland• Also called __________________. • Consists of unmyelinated axons of hypothalamic

neurons.• Release ADH and Oxytocin to target organs

– produced in hypothalamus– transported by hypothalamo-hypophyseal tract

• ADH– targets ____________; - effects _________

• Oxytocin– targets ____________; - effects _________a. Kidneys- increase reabsorption of waterb. Uterus- contraction during labor (child birth)c. Breast- milk ejection (let-down)d. Both b and c

Clinical Correlation • Pituitary dwarfism = hyposecretion of growth

hormone• Gigantism = hypersecretion of ____________. • Acromegaly = hypersecretion of __________;

thickening of bones and soft tissues. • Diabetic insipidus = hyposecretion of _______ a. ADH b. growth hormone in childhood c. Aldosterone d. growth hormone in adult

Learning Objectives II: Thyroid, Parathyroid, Adrenal Glands

1. Describe the structure of thyroid gland and identify the hormones produced and their functions.

2. Discuss the location of the parathyroid glands and the functions of the hormone they produce.

3. Discuss the adrenal glands as to structure and functions of the hormones they produce.

4. Discuss the effects of abnormal levels of hormones production of these endocrine organs.

Thyroid Gland Anatomy

• Largest endocrine gland; high rate of blood flow

• Located just inferior to thyroid cartilage

• Two lobes connected by isthmus

• Produces T3 and T4

• Size affected by factors: age, radioactive exposure, heredity, diet

Thyroid Gland• Composed of thyroid follicles filled with colloid. • Follicular cells secrete ____.

– Increase • BMR and O2 consumption

• calorigenic effect (heat production) • HR and contraction• RR• appetite and breakdown CHO, lipids and proteins

• C (clear/parafollicular) cells produce ___.

- effects: decrease blood Ca2+ , increase Ca2+ deposition and bone formation especially in children

a. Calcitonin b. Thyroid hormone (T3 and T4)

Thyroid Hormone Synthesis1. Iodide absorption and oxidation2. Thyroglobulin synthesis and secretion3. Iodine added to tyrosine of thyroglobulin4. Thyroglobulin uptake and hydrolysis5. Release of T3 (triiodothyronine) and T4

(thyroxine) into the blood

Thyroid Gland Disorders• Cretinism- Congenital hypothyroidism

– infant suffers abnormal bone development, thickened facial features, low temperature, lethargy, brain damage

• Myxedema- Adult hypothyroidism– low metabolic rate, sluggishness, sleepiness, weight

gain, constipation, dry skin and hair, cold sensitivity, blood pressure and tissue swelling

• Endemic goiter: size of gland is ______. – dietary deficiency of ________, no TH, no negative

feedback, TSH

• Toxic Goiter- also called _______________– antibodies mimic TSH, TH, exophthalmos

Parathyroid Glands

• Located at posterior surfaces of _______.• 2 cell populations: chief cells and oxyphil

cells.

• What hormone is secreted by chief cells and discuss it’s effects to target organs?a. Calcitoni b. PTH c. T4 d. Calcitriol

Parathyroid Disorders• Hypoparathyroid: Tetany

– surgical excision during thyroid surgery– results to decrease calcium secretion– fatal in 3-4 days

• Hyperparathyroid = excess calcium secretion– tumor in gland– causes soft, fragile and deformed bones blood Ca2+

– renal calculi

Adrenal GlandI - Adrenal Cortex a) zona glomerulosa- Mineralocorticoids

(Aldosterone) - promotes _____ and _____ retention and potassium excretion

b) zona fasciculata- Glucocorticoids (Cortisol, Corticosteroid)– stimulate fat and protein catabolism, gluconeogenesis

and release of fatty acids and glucose into blood– anti-inflammatory effect becomes immune with long-term

use c) zona reticularis- Sex steroids (Androgen)

- Stimulates development of pubic hair before pubertyII – Adrenal Medulla - Cathecolamines

Adrenal Medulla

• Sympathetic ganglion innervated by sympathetic preganglionic fibers – consists of modified neurons called ___________ cells– stimulation causes release of _________ hormones.

• Hormonal effect is diffuse– alertness, anxiety, or fear– ____________ BP, heart rate and air flow– ____________ metabolic rate

• inhibits insulin secretion• stimulates gluconeogenesis and glycogenolysis

Adrenal Disorders• Addison’s disease = primary adrenal

insufficiency

- results in decrease of glucocorticoids

- lethargy, weight loss, and hypoglycemia • Cushing’s syndrome

- results in increase of glucocorticoids

– hyperglycemia, hypertension, weakness, edema

– buffalo hump on the back and moon face

Homework (Self-Review) 1. Define: cushing syndrome, acromegaly, cretinism, toxic

goiter, enemic goiter, addison disease, and tetany. 2. Discuss hypothalamic- hypophyseal feedback mechanism

on regulation of thyroid hormone secretions. 3. Name the endocrine organ that produces (secretes) or

releases the following hormones and give its effect/s on their target organ/s: - oxytocin, thyroxine (T4), prolactin (lactogenic hormone), ACTH, ADH (vasopressin), growth hormone, PTH, calcitonin, aldosterone,TSH, MSH, glucocorticoids, and epineprine and nor-epinephrine.

4. Discuss the homeostatic regulation of blood calcium as to hormones and effects on target organs.

5. Give the hormone secreted by the following cells: parafollicular cell, supraoptic nucleus, follicular cell, chief cell, chromaffin cells, and paraventricular nucleus.

6. Compare and contrast mechanisms of cell communications.

Learning Objectives III: Pineal gland, Pancreas, and Other Endocrine Tissues1. Discuss the structure and hormonal functions of pineal

gland.2. Describe the endocrine portion of pancreas and

identify the hormones produced and their functions.3. Describe the functions of the hormones produced by

the kidneys, heart, thymus, testes, ovaries, and adipose tissues.

4. Explain how hormones interact to produce coordinated physiological response.

5. Define general adaptation syndrome and hormonal responses to stress.

Pineal Gland• Located at posterior portion of roof of 3rd ventricle• Peak secretion ages 1-5; by puberty 75% lower• ___________ cells produce hormones called

________ • Functions – inhibits reproductive functions,

protects against damage from free radicals, and sets circadian rhythms(sleep-wake cycle)

• Melatonin in SAD

a. pinealocytes b. chief cells c. PTH d. melatonin

Pancreas• Retroperitoneal • Lies between inferior border of stomach and

duodenum • Exocrine: ____________

- 99%; produce _______• Endocrine: ___________

- 1%; produce ________a. islets of Langerhans b. pancreatic acini

c. hormones d. digestive enzymes

Pancreatic Hormones• Glucagon from ________ cells

– secreted in very low carbohydrate and high protein diet or fasting– stimulates glycogenolysis, fat catabolism and promotes

absorption of amino acids for gluconeogenesis– Effects on blood glucose is ____________________

• Insulin from ___________ cells – secreted after meal with CHO– stimulates glucose and amino acid uptake– stimulates glycogen, fat and protein synthesis– Effects on blood glucose is ____________________

• Somatostatin (GH- IH) from ______ cells– secreted with rise in blood glucose and amino acids after a meal– inhibits secretion of insulin & glucagon by and cells

• Pancreatic polypeptide from ______ cells- inhibits gallbladder contractions- regulates production of pancreatic enzymes

Diabetes Mellitus• Type I- due to autoimmune deficiency of B cells;

absence of insulin; need insulin shots • Type II- due to insulin resistance; associated

with obesity and over 40 y/o; manage by diet, exercise and oral medications

• Signs and symptoms of hyposecretion of insulin– 3 P’s ____________________

____________________ ____________________

– hyperglycemia, glycosuria, ketonuria– osmotic diuresis

Thymus

• Location: __________, superior to the heart.

• Involution after puberty• Secretes hormones (thymosins) that

regulate development and later activation of T lymphocytes

a. Abdominal cavity b. Mediastinumc. Cervical region d. Cranial fossa

Ovary• Granulosa/ follicular cells produces ________• Corpus luteum produces predominantly _____,

and small amount of _____. • Hormonal Functions

_______- maturation of follicles, secondary sex characteristics_______- prepare for implantation and mammary gland secretory activity

• Both secrete inhibin: suppresses FSH secretion

a. Progesterone b. Estrogen c. FSH d. LH

Testes

• Interstitial/Leydig cells produce_______

- Describe hormonal functions.

• Sustentacular/sertoli cells

– secrete inhibin which suppresses FSH secretion

a. Testosterone b. FSH-LH

c. Gametes d. Progesterone

Endocrine Functions of Other Organs

• Adipose tissue- Leptin = stimulates sense of satiety

• Heart – Atrial Natriuretic Peptide (ANP) released with an

increase in BP Na+ and H2O loss by kidneys– Effects: _________ blood pressure

• kidneys– Erythropoietin = stimulates production of __________– Renin – angiotensinogen = stimulates reabsorption of

__________• precursor of angiotensin II

– converts vitamin D3 to Calcitriol = stimulates _______

Endocrine Functions of Other Organs

• Stomach and small intestines

- Enteric hormones coordinate digestive

motility and secretion

• Placenta– secretes estrogen, progesterone and others

• regulate pregnancy, stimulate development of fetus and mammary glands

Hormone Interactions

a) Interactive effects

- produce different but complementary results

b) Synergistic effects

- additive effects of 2

hormones

c) Permissive effects– one hormone enhances

response to a second hormone

d) Antagonistic effects

- opposing

• Identify the patterns of hormonal interactions

1. Effect of PTH and calcitonin

2. Epinephrine increases energy consumption when thyroid hormones are present.

3. Glucose sparing action of GH and glucocorticoids

4. Effect of calcitriol and PTH

Stress and Adaptation

• Stress– upsets homeostasis and threatens one’s

physical/emotional well-being

• General adaptation syndrome – way body reacts to stress– occurs in 3 stages

1.Alarm phase

2.Resistance phase

3.Exhaustion phase

Alarm Phase

• Initial response epinephrine and norepinephrine levels HR and BP; blood glucose levels

• Sodium and water retention

Resistance Phase

• After a few hours, glycogen reserves gone ACTH and cortisol levels• Fat and protein breakdown• Gluconeogenesis• Depressed immune function• Susceptibility to infection and ulcers

Exhaustion Phase

• Stress that continues until fat reserves are gone

• Protein breakdown and muscle wasting • Loss of glucose homeostasis• Hypertension and electrolyte imbalances

(loss of K+ and H+)• Hypokalemia and alkalosis leads to death

Homework (Self-Review) 1. Discuss the regulation of blood glucose

metabolism.

2. Compare and contrast Type 1 and Type 2 diabetes mellitus.

3. List the hormone/s secreted or released by the following and its effect/s to target organ/s : - leydig cell, beta pancreatic cell, delta pancreatic cell, ovarian follicular cell, pinealocytes, corpus lutein cell, thymus, adipose tissue, and kidneys.

4. Discuss the 3 stages (phases) of body’s adaptation to stress.