patho unit 6 ch. 18

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  1. Hormones
    • hormones are mediator molecules that are secreted directly in the blood by endocrine glands
    • Hormone receptors are located on the plasma membrane or in the intracellular compartment of a target cell
    • Hormones operate by negative or positive feedback- most are negative feedback
  2. The Endocrine System
    Endocrine system proper (exclusively endocrine) consists of the pituitary, thyroid, parathyroid, adrenal and pineal glands
  3. What are some other organs  and tissues that secrete hormones, but are not exclusively endocrine glands?
    Hypothalamus, thymus, pancreas, gonads, kidneys, stomach, liver, small intestine, skin, heart & placenta
  4. Action of Hormones
    • Control of the composition and the volume of the internal environment 
    • Emergency control during physical and mental stress
    • Integration of growth and development
    • Reproductive control
    • Regulate metabolism and energy balance
    •   -Glucose availability and metabolic rates (Gluconeogenesis)
  5. True or False
    Hormones cause longer lasting effects than neurotransmitters
  6. Action of Hormones:
    If hormones are secreted into the blood and circulate through the body, why aren't there widespread effects from the hormone?
    • There are, but only at specific target cells (tissue)
    • They bind to specific protein or glycoprotein receptors on the target cells
    •   -For example, thyroid stimulating hormone (TSH), only effects the thyroid gland
    • Target cells have the ability to up- or down-regulate receptors
  7. Alterations of Endocrine Function
    • Inappropriate amounts of hormone delivered to target cell
    • Inappropriate response by target cell
    • Hypersecretion
    • Hyposecretion 
  8. Alteration of Endocrine Function:
    • having too much hormone or having something else act like a specific hormone
    •   -Glandular neoplasms
    •   -Ectopic hormone release
    •   -Antibody mimicking hormone
  9. Alteration of Endocrine Function:
    • lack or decrease of hormone, or lack or decrease in hormone receptors
    •   -Receptor disorders
    •   -Inadequate hormone synthesis
    •   -Degraded or inactivated hormones
    •   -Blocking antibodies
  10. Pituitary and the Hypothalamus:
    What is the major link between the nervous system and the endocrine system?
    • The Hypothalamus
    • It receives input from several regions in the brain: limbic, RAS, thalamus
    • The anterior lobe of the pituitary (adenohypophysis) is anatomically and functionally connected to the hypothalamus by blood vessels
    • The posterior lobe of the pituitary (neurohypophysis) is anatomically and functionally connected to the hypothalamus by neurosectretory neurons
  11. The Posterior Pituitary
    • Oxytocin (OT) and ADH are secreted by the posterior pituitary in response to nerve impulses from the neurosecretory neurons
    • Childbirth, suckling, and coitus stimulate oxytocin release
    • Dehydration stimulates ADH release
  12. True or False
    Diseases of the posterior pituitary are rare and are usually related abnormal oxytocin secretion
    False, abnormal ADH sectretion
  13. Pituitary Disorders
    • Antidiuretic hormone (ADH)
    •   -controls cells at the distal collecting tubule (DCT)of the kidney to prevent secretion of water
    •    -increases aquaporin (water channel protein) production by DCT cells
    •    -ADH allows water to be reabsorbed into the body
    • ADH thereby decreases the plasma osmolality (concentration)
    • it also decreases urine output (UOP)
  14. Syndrome of Inappropriate ADH (SIADH)(hypersecretion disorder)
    • In states of dehydration, releasing ADH is the right thing to do
    • SIADH occurs when ADH is secreted despite normal or even elevated levels of body water, and without the absence of normal physiologic stimuli as in thirst.
    •   -This results in an inability to excrete excess water in the urine, and reabsorption of water to the point of causing hypervolemia and hyponatremia
    • SIADH- secrete to much ADH, produce too many aquaporins, and reabsorb too much water
  15. SIADH (cont.)
    • As excess body water continues to rise serum sodium levels continue to fall, and more water is shifted intracellularly 
    •   -Cellular edema leads to headache and other neurological signs and symptoms
    •   -At the same time the body is retaining water, the urine is inappropriately concentrated 
    • (dilutes our sodium levels causing hyponatremia, causing edema)
  16. Diabetes Insipidus
    • Produces large volumes of very dilute urine (tasteless)
    • it is the opposite of SIADH: DI is caused by the insufficient release of ADH despite dehydration
    • With insufficient ADH secretion free water continues to be eliminated in the urine, even though it is needed in the body
    •   -normal urinary output is 1-1.5 L/day
    •   -With DI, urinary output is >2.5 L/day
    •    -50% of patients: 4-8 L/day
    •    -25% of patients: 8-12 L/day
  17. What are the two types of Diabetes Insipidus?
    • Neurogenic (most common), results from a lesion in the hypothalamus, pituitary, or infundibulum resulting in decreased ADH secretion (not secreting ADH)
    • Nephrogenic is a state of insensitivity of the renal tubules to ADH (doesn't respond to ADH)
  18. Hormones of the Anterior Pituitary
    • The anterior pituitary consists of groups of specific cells that each secrete a specific type of hormone
    • see. slide on p.242-243
  19. Anterior Pituitary Disorders:
    • Infarction of the gland
    • Removal/ destruction of the pituitary
    • Space-occupying pituitary adenomas 
    • Aneurysms that cause compression (limits blood supply)
  20. Anterior Pituitary Disorders:
    • Absence of all hormones
    • Treatment may consist of replacing HGH, ACTH, TSH, and sex hormones
  21. Disorder of HGH Secretion: 
    • Depends on the affected hormone
    • Pituitary dwarfism results from insuficient HGH release during an individual's growth phase.
    •   -patient has normal face and intelligence, with normal body proportions
    •   -compare Achondroplasia-disorder of bone or cartilage development
    •     -Bone-growth disorder responsible for 70% of dwarfism.
    •     -Limbs are proportionately shorter than trunk with a larger head than average and characteristic facial features.
  22. Disorder of HGH Secretion: 
    • the most common cause of excess secretion of the hormones of the adenohypophysis is a pituitary adenoma
    •   -Giantism results from excess HGH during an individuals growth phase
    •    -This his now a fairly rare disorder because of early detection of adenomas
  23. Disorder of HGH Secretion: 
    • hypersecretion of HGH during adulthood
    • is marked by enlargement and elongation of the bones of the face, jaw, cheeks, and hands
    • the long bones of the extremities are unaffected because the growth plates are closed
    • With bony and soft tissue overgrowth, nerves can be entrapped
    •   -the patient may demonstrate muscle weakness, foot drop, and sensory changes
    •   -There is also an increase in the size and function of sebaceous and sweat glands (leading to acne and increased body odor)
  24. Thyroid Gland
    • it has two lateral lobes and is located inferior to the larynx
    • the gland stores a 100 day supply of hormones in sacs (thyroid follicles) that make up most of the gland
    •   -Two hormones are secreted: Thyroxine (T4)and Triiodothyronine (T3)
  25. What do Thyroid Hormones do?
    • Thyroid hormones:
    • Regulate oxygen use
    • Increase the basal metabolic rate (BMR)
    • Increase cellular carbohydrate and protein catabolism 
    • Increase reactivity of the nervous system
    • Along with HGH, controls tissue growth and developent
  26. Thyroid Hormones
    See slides on p. 245
  27. Thyroid Hormone Release is Controlled by a Homeostatic loop
    see p.246
  28. Thyroid Disorders:
    • An enlarged thyroid gland due to increase demand for thyroid hormones, or anything that causes and increase of TSH
    •   -Goiters can occur in states of euthyroid, hypothyroidism, and hyperthyroidism
    •    -common causes include iodine deficiency, viral or genetic disease, puberty, and pregnancy
    • If you don't have iodine you can't produce T3 and T4 hormones
  29. Thyroid Disorders:
    Graves Disease
    • A autoimmune disorder where antibodies are made against TSH receptors of thyroid cells 
    •   -The antibodies act as TSH receptor agonists (i.e. they turn on the production of thyroxin)
    • Excess thyroxin secretion leads to thyrotoxicosis (symptomatic hyperthyroidism)
    • symptoms: nervousness
    • Signs:
    •   -diminished body weight
    •   -exopthalmos (bulging eyes) due to periobital connective deposition
    •    -causes the tissue to push the eye ball forward, causes eye damage to the cornea
  30. Thyrotoxic Crisis ("Thyroid Storm")
    • A very dagerous worsening of the thyrotoxic state
    •   -Now rare, but still dangerous
    • Manifests as hyperthermia, tachycardia, nausea and vomiting, diarrhea, high-output heart failure, agitation delerium
    •   -if untreated, patients can die within 48 hours
    • Treatment- prevent the patient from becoming hyperthyroid in the first place by blocking hormone production or ablating the gland ( surgery or radiation therapy)
  31. Hypothyroidism
    • Low levels of circulation thyroid hormone is the most common abnormal thyroid finding- it can be a primary abnormality, or appear secondary to another disorder:
    •   -Primary causes include Hashimoto disease (an autoimmune destruction of the thyroid gland)
    •   -Secondary causes include Toxic Thyroiditis from a bacterial infection of the thyroid and hypothyroidism as a complication of thyroid surgery
  32. Myxedema (slippery edema)
    • a rare but serious form of severe hypothyroidism that results from prolonged insufficient thyroxin during adulthood
    •   -the "myxedema" comes from deposition of connective tissue fivers separated by excessive protein and mucopolysacharides (these bind water, causing boggy edema)
    •   -It results in dry brittle hair, dry skin due to decrease perspiration and sebaceous gland secretion, lethargy, low basal metabolic rate (low temp and heart rate); patients gain weight easily
  33. Myxedema coma
    • A CNS-cardiovascular complication of the disease presenting as hypothermia (no shivering), hypoventilation, hypotension, hypoglycemia, lactic acidosis, and a deterioration of mental status
    •   -it is a medical emergency, and if not promptly treated will result in permanent brain damage or death
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patho unit 6 ch. 18
patho unit 6 ch. 18
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