Endocrine System: Katy Colindres

Endocrine System: Katy Colindres - Period 6

Major Endocrine Glands/Organs and Their Functions

Major Functions of the Endocrine System

Steroid VS. Non-Steroid

Diseases Associated with the Endocrine System

Homeostatic Mechanisms of Hormone Regulation

acts with nervous system to coordinate and integrate activity of body cells

influences metabolic activities via hormones transported in blood

controls and integrates:

reproduction

growth and development

maintenance of electrolyte, water, and nutrient balance of blood

regulation of cellular metabolism and energy balance

mobilization of body defenses

endocrine glands (produce hormones; lack ducts)

pituitary

thyroid

parathyroid

adrenal

pineal

pancreas

gonads

hypothalamus

thymus

steroid

non-steroid (amino acid-based)

amino acid derivatives, peptides, and proteins

synthesized from cholesterol

gonadal and adrenocortical hormones

lipid-soluble

connected to pituitary gland (hypophysis) via stalk called infundibulum

secretes at least eight major hormones

two major lobes:

posterior pituitary:

anterior pituitary:

made up of neural tissue that secretes neurohormones

(adenohypophysis) consists of glandular tissue

posterior lobe, along with infundibulum, make up the neurohypophysis

ovary (female)

testis (male)

blood level of hormones

controlled by negative feedback

increased hormone effects on target organs can inhibit further release of hormones

vary only within narrow, desirable range

posterior lobe

secretes two neurohormones (oxytocin and ADH)

hormones stored in axon terminals in posterior pituitary and are released into blood when neurons fire

secretes releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion

diabetes insipidus

ADH deficiency due to damage to hypothalamus or posterior pituitary

must keep well hydrated

oxytocin

ADH

strong stimulant of uterine contractions released during childbirth

acts as hormonal trigger for milk ejection

acts as neurotransmitter in brain

positive feedback mech

hypothalamus contains osmoreceptors that monitor solute concentrations

if concentration too high, posterior pituitary triggered to secrete ADH

targets kidney tubules to reabsorb more water to inhibit or prevent urine formation

release also triggered by pain, low blood pressure, and drugs

inhibited by alcohol, diuretics

high concentrations cause vasoconstriction, also called vasopressin

positive feedback mech

growth hormone (GH)

thyroid stim hormone (TSH)

adrenocorticotropic hormone (ACTH)

follicle stim hormone (FSH)

luteinizing hormone (LH)

prolactin (PRL)

direct actions on metabolism and indirect growth-promoting actions

hypersecretion of GH is usually caused by anterior pituitary tumor

in children results in gigantism, can reach heights of 8 feet

in adults results in acromegaly, overgrowth of hands, feet, and face

hyposecretion of GH

in children results in pituitary dwarfism, may reach height of only 4 feet

in adults usually causes no problems

stim normal development and secretory activity of thyroid

inhibited by rising blood levels of thyroid hormones

stim adrenal cortex to release corticosteroids

secreted by gonadotropic cells

stim production of gametes (egg or sperm)

promotes production of gonadal hormones

in females, helps mature follicles of egg, triggers ovulation and release of estrogen and progesterone

in males, stim production of testosterone

absent from blood in prepubertal boys and girls

stim milk production in females

role in males not well understood

butterfly shaped gland in anterior neck on trachea, just inferior to larynx

thyroid hormone

major metabolic hormone; affects virtually every cell in body

thyroxine

triiodothyronine

triggers transcription of various metabolic genes

increases basal metabolic rate and heat production

regulates tissue growth and development

maintains blood pressure

TH release is regulated by negative feedback

falling TH levels provide negative feedback inhibition on TSH

TSH can also be inhibited by GHIH, dopamine, and increased levels of cortisol and iodide

hyposecretion of TH in adults can lead to myxedema

low metabolic rate, thick and/or dry skin, puffy eyes, feeling chilled, constipation, edema, mental sluggishness, lethargy

if due to lack of iodine, a goiter may develop

lack of iodine decreases TH levels, which triggers increased TSH secretion, triggering thyroid to make more and more unusable thyroglobulin

thyroid enlarges

congenital hypothyroidism is usually caused by poor development of thyroid gland

pituitary problems or maternal medications may sometimes rarely affect baby's ability to make TH

may be asymptomatic or present with weak cry, poor feeding, constipation or prolonged jaundice

TH replacement is crucial and is usually lifelong

hypersecretion of TH: most common type of Graves' disease

autoimmune disease: body makes abnormal antibodies directed against thyroid follicular cells

antibodies mimic TSH, stimulating TH release

symptoms include elevated metabolic rate, sweating, rapid and irregular heartbeats, nervousness, and weight loss

exophthalmos may result: eyes protrude as tissue behind eyes becomes edematous and fibrous

treatments:

surgical removal of thyroid or radioactive iodine to destroy active thyroid cells

four to eight tiny yellow brown glands embedded in posterior aspect of thyroid

secrete parathyroid hormone, or parathormone

most important hormone in Ca2+ homeostasis

secreted in response to low blood levels of calcium

inhibited by rising levels of calcium

target organs are skeleton, kidneys, and intestine

stim osteoclasts to digest bone matrix and release calcium to blood

enhances reabsorption of calcium and secretion of phosphate by kidneys

promotes activation of vitamin D by kidneys, which leads to increased absorption of calcium

paired, pyramid shaped organs atop kidneys

structurally and functionally it is two glands in one

adrenal cortex: three layers of glandular tissue that synthesize and secrete several different hormones

adrenal medulla: nervous tissue that is part of sympathetic nervous system

produces over 24 different hormones collectively called corticosteroids

three layers of cortical cells produce the 3 different corticosteroids

mineralocorticoids

glucocorticoids

gonadocorticoids

regulate electrolyte concentrations

aldosterone: most potent mineralocorticoid

stim sodium reabsorption by kidneys

stim potassium elimination by kidneys

results in increased blood volume and blood pressure

effects are short lived

influence metabolism of most cells and help us resist stressors

keep blood glucose levels relatively constant

maintain blood pressure by increasing action of vasoconstrictors

hormones include:

cortisol (hydrocortisone); only glucocorticoid in significant amounts in humans

cortisone

corticosterone

regulation of secretion

cortisol released in response to ACTH

cortisol secretion cycles are governed by patterns of eating and activity

acute stress (infection, physical or emotional trauma) interrupts cortisol rhythm

causes increase in blood levels of glucose, fatty acids, and amino acids

cushing's disease

depresses cartilage/bone formation and immune system; inhibits inflammation; disrupts neural, cardiovascular, and gastrointestinal function

causes: tumor on pituitary, lungs, pancreas, kidney, or adrenal cortex; overuse of corticosteroids

cushingoid signs: "moon" face and "buffalo hump"

treatment: removal of tumor, discontinuation of drugs

addison's disease

usually involves deficits in both glucocorticoids and mineralocorticoids

decrease in plasma glucose and sodium levels

weight loss, severe dehydration, and hypotension are commont

treatment: corticosteroid replacement therapy

early sign is characteristic bronzing of skin due to high levels of ACTH which triggers melanin production in melanocytes

adrenal sex hormone

weak androgens (male sex hormones) converted to testosterone in tissue cells, some to estrogens

may contribute to:

onset of puberty and appearance of secondary sex characteristics

sex drive in women

source of estrogens in postmenopausal women

synthesize catecholamines epinephrine (80%) and norepinephrine (20%)

effects of catecholamines:

vasoconstriction

increased heart rate

increased blood glucose levels

blood diverted to brain, heart, and skeletal muscle

both have basically same effects, but:

epinephrine is more a stimulator of metabolic activities

norepinephrine has more of an influence on peripheral vasoconstriction and blood pressure

like bronchial dilation and blood flow to skeletal muscles and heart

small gland hanging from roof of third ventricle

secrete melatonin, derived from serotonin

melatonin may affect:

timing of sexual maturation and puberty

day/night cyles

physiological processes that show rhythmic variations (body temperature, sleep, appetite)

production of antioxidant and detoxification molecules in cells

triangular gland located partially behind stomach

has both exocrine and endocrine cells

pancreatic islets (islets of Langerhans) contain endocrine cells

alpha cells produce glucagon (hyperglycemic hormone)

beta cells produce insulin (hypoglycemic hormone)

secreted when blood glucose levels increase

extremely potent

raises blood glucose levels by targeting liver to:

triggered by decreased blood glucose levels, rising amino acid levels, or sympathetic nervous system

break down glycogen into glucose

synthesize glucose from lactic acid and other noncarbohydrates

release glucose into blood

insulin lowers blood glucose levels in 3 ways:

enhances membrane transport of glucose into fat and muscle cells

inhibits breakdown of glycogen to glucose

inhibits conversion of amino acids or fats to glucose

diabetes mellitus

can be due to:

hyposecretion of insulin: type 1

hypoactivity of insulin: type 2

three cardinal signs:

polyuria: huge urine output

polydipsia: excessive thirst

polyphagia: excessive hunger and food consumption

cells cannot take up glucose and are "starving"

glucose acts as osmotic diuretic

from water loss due to polyuria

when sugars cannot be used as fuel, as in DM, fats are used, causing lipidemia: high levels of fatty acids in blood

fatty acid metabolism results in formation of ketones (ketone bodies)

ketones are acidic, and their build-up in blood can cause ketoacidosis

also causes ketonuria: ketone bodies in urine

untreated ketoacidosis causes hyperpnea, disrupted heart activity and oxygen transport, and severe depression of nervous system that can possibly lead to coma and death

hyperinsulinism

excessive insulin secretion

causes hypoglycemia: low blood glucose levels

anxiety, nervousness, disorientation, unconsciousness, even death

treatment: sugar ingestion

gonads produce same steroid sex hormones as those of adrenal cortex, just lesser amounts

estrogen

progesterone

maturation of reproductive organs

appearance of secondary sexual characteristics

with estrogen, causes breast development and cyclic changes in uterine mucosa

produce testosterone

initiates maturation of male reproductive organs

causes appearance of male secondary sexual characteristics and sex drive

necessary for normal sperm production

maintains reproductive organs in functional state

placenta

secretes estrogens, progesterone, and human chorionic gonadotropin

large in infants and children; shrinks with age

thymulin, thymopoietin, and thymosins may be involved in normal development of T lymphocytes in immune response