Endo 3 Flashcards
What percentage of thyroid hormones is T3?
7%
What percentage of thyroid hormone is T4?
93%
Is T3 or T4 more potent?
T3
What does calcitonin do to calcium levels?
decrease calcium levels
What do thyroid hormones do to catecholamines?
have a permissive action
(action is greater than the sum of the two parts)
Where is calcitonin secreted from?
parafollicular cells
Where is thyroglobin stored?
in the colloid of the thyroid follicle
What element is required for the formation of thyroid hormones?
iodine
What helps to increase the intracellular concentrations of iodine?:
Na/I symporters
What is the anion exchanger that allows iodine to exit the thyrocyte to access the colloid?
pendrin (Cl/I exchanger)
Where are T3 and T4 made?
in the colloid
What enzyme is required for the formation of thyroid hormones?
peroxidase
What do T3 and T4 bind to?
thyroglobin
What are the steps of T3 and T4 secretions into the blood?:
- colloid is internalized by endocytosis
- vesicles fuse with lysosomes in the cell
- proteases cleave T3 and T4 from TG
- T3 and T4 diffuse out of the cell and into capillaries
What are plasma proteins that T3 and T4 bind to?
thyroxin binding globulin, transthyretin, and albumin
Does T3 or T4 have a longer half life?
T4
What converts T4 to T3?
deiodinase
How can individual cell types regulate amounts of active thyroid hormone?
regulating deiodinase activity
What is unique about deiodinases?
they have selenocysteines that contain selenium in place of sulfur
What are some things that can inhibit deiodinase activity?
selenium deficiency, burns, trauma, advanced cancer, cirrhosis, chronic kidney disease, MI and febrile states, fasting, and stress
What would deiodoninase insufficiency appear similar to?
signs of hypothyroidism
Does T3 or T4 actions occur sooner?
T3
What are the cardiovascular effects of thyroid hormones?
increase cardiac output, tissue blood flow, heart rate, heart strength, and respiration
What are the metabolic effects of thyroid hormones?
increase mitochondria, Na/K ATPase, O2 consumption, glucose absorption, gluconeogenesis, glycogenolysis, lipolysis, protein synthesis, and BMR
Where does negative feedback of thyroid hormone occur?
in the anterior pituitary
What is the main circulating form of thyroid hormone?
T4
What type of release is thyroid hormone?
pulsatile
-output starts to raise at 9pm
-peaks at midnight
-declines during the day
How does thyroid hormone stimulate carbohydrate metabolism?
-cause uptake of glucose by cells
-enhance glycolysis and gluconeogenesis
-increase rates of CHO absorption from GI tract
How does thyroid hormone stimulate fat metabolism?
-increase lipid mobilization and oxidation of fatty acids by the cells
-required to convert beta carotene to vitamin A
-decreases circulating cholesterol levels
How do thyroid hormones effect the nervous system?
-required for normal development
-impact reflex time
-muscle tremors due to increased reactivity of neuronal synapses
-feeling of tiredness, but difficulty sleeping
-anxiety, worry, and paranoia
How do thyroid hormones effect the cardiovascular system?
-increased expression of beta adrenergic receptors
-increased blood flow, heart rate, and heart contractility
How do thyroid hormones effect the endocrine system?
-activation of bone formation causes a need for increase PTH secretion
How do thyroid hormones effect the GI system?
-increased appetite and food intake
-increased rate of secretion and motility of GI tract
What does hypothyroidism do with poop?
constipation
What does hyperthyroidism do with poop?
diarrhea
What is goiter?
enlarged thyroid that does indicate functional status
What causes goiter?
excessive amounts of TSH secretion
-die to increase TSH bound to thyroglobin in the colloid of the follicles
What is a disease associated with hyperthyroidism?
Graves disease
What is Grave’s disease?
autoimmune disease that has thyroid stimulating immunoglobins that stimulate the thyroid gland to secrete excess thyroid hormones
What are the levels of the hormones in Grave’s disease?
decreased TRH, decreased TSH, and increased T3 and T4
What are the treatments of hyperthyroidism?
radioactive I for thyroid ablation
-propanolol as a beta blocker to suppress the sympathetic response caused by thyroid hormones
-L-thyroxine is given to replace the thyroid hormones that can not be made anymore
What are the oral symptoms of hyperthyroidism?
burning mouth syndrome, gum disease, excessive salivation, weakening of mandible, increased caries risk
What is thyroid storm?
elevated thyroid hormone with stressful events or seriousillness
What are symptoms of thyroid storm?
fever, tachycardia, elevated BP, nausea, vomiting, diarrhea, breathing problems
What should you avoid if a person is experiencing thyroid storm?
epinephrine
What is Hashimoto’s thyroiditis?
disease associated with hypothyroidsm
-autoimmune reaction against thyroid gland destroys gland rather than stimulating it
What is the treatment of hashimotos?
L-thyroxine
-due to needing more thyroid homrone since the thyroid gland has been fiborisezed whateber
Does hypothryoidism with iodide or TSH deficiency cause a goiter?
iodide deficiency
Is hypothyroidism due to an iodide deficiency a primary or secondary disorder?
primary
-the iodine is added in the thyroid gland which is the last step
What are some symptoms of hypothyroidism?
coarse, dry, and brittle hair
loss of lateral eyebrows
pallor
macroglossia
weight gain
peripheral edema
lethargy and impaired memory
periorbital edema and puffy face
deep, coarse voice
diminished perspiration, cold intolerance
slow pulse, enlarged heart
gastric atrophy
constipation
menorrhegia
muscle weakness
What type of patients can experience myxedema?
severely hypothyroid patients
What causes myxedema?
increased quantities of hyaluronic acid and chondroitin sulfate bound with protein plus water accumulate in skin
What causes cretinism?
-congenital absence of thyroid gland
-iodine deficient diet (most common cause worldwide)
What does cretinism cause?
causes physical and mental retardation of neonates
-skeletal growth is more inhibited than soft tissue growth
(obese, stocky, and short with large protruding tongue)
What are the oral manifestations of hypothyroidism?
-macroglossia
-dysgeusia
-poor wound healing and increase risk of infection (decreases activity of fibroblasts)
-increases periodontal disease
-salivary gland enlargement
What type of drugs are patients with hypothyroidism sensitive to?
depressants and barbiturates
Where is the body’s phosphate stored?
-85% in bones
-14-15% in cells
-less than 1% in EC fluid
Where is the body’s calcium stored?
-0.1% in EC fluid
-1% in cells and organelles
-the rest is in the body (bones?)
What happens when the body’s calcium is too low?
neuronal hyper-excitability (tetany)
What happens when the body’s calcium is too high?
neuronal depressionW
What are the three main ways the body can maintain calcium and phosphate levels?
-absorption via intensity
-excretion via urine and feces
-temporary storage via bones
What are the three hormones that regulate the plasma calcium?
- Parathyroid hormone
- Calcitriol
- Calcitonin
What does parathyroid hormone do to the levels of calcium and phosphate?
increase plasma calcium and decrease phosphate
What does calcitriol do to the levels of calcium and phosphate?
increase plasma calcium and phosphate
What does calcitonin do to the levels of calcium and phosphate?
decrease plasma calcium and phosphate
What is the primary hormone that enhances intestinal of calcium?
calcitriol
What are the actions of PTH that change the plasma concentrations of calcium and phosphate?
-mobilize calcium from bone
-enhance renal reabsorption of calcium
-increases intestinal absorption of calcium (indirectly)
How do Vitamin D3 and PTH stimulate bone resorption>
in times of decreased calcium, osteoblasts will secrete RANKL
-RANKL binds to the osteoclasts and activate them
-osteoclasts will start to break down bone to increase plasma calcium
How does calcitonin stimulate bone deposition?
_OPG is released and binds to RANKL
-RANKL can no longer activate osteocalsts
-osteoblasts will apoptose
What are risk factors for osteoporosis?
-vitamin D deficiency
-inadequate calcium intake
-glucocortioid medications
-reduced physical activity
-estrogen deficiency
What are the treatments for osteoporosis?
-exercise
-physical therapy
-estrogen
-calcium
-vitamin D
disphosphonates
What are the parathyroid glands?
four pea sized glands on posterior surface of the thyroid gland
What secretes PTH? (cell type)
chief cells
What can cause hypertrophy of parathyroid gland?
pregnancy, rickets, lactation
What can decrease the size of the parathyroid gland?
-increased vitamin D intake
-excess quantities of calcium in the diet
-bone resportion caused by factors other the PTH
How does PTH increase plasma calcium?
-bone resorption
-reabsorption of calcium by renal tubule which reduces excretion
-make active vitamin D which causes intestinal calcium absorption
How does PTH decrease plasma phosphate?
decreases reabsorption by renal tubules leading to increased urinary secretion
What three places help to make calcitriol?
skin, liver, kidney, and intestinal epithelium
What type of hormone is calcitonin?
peptide hormone
-secreted by parafollicular cells
Is calcitonin a major controlled of Calcium in humans?
nah
What is primary hyperparathyroidism?
excess PTH secretion due to a parathyroid gland tumor
What does primary hyperparathyroidism cause?
extreme osteoclastic activity in bone
-cystic bone disease
What are some of the symptoms of primary hyperparathyroidism?
-hypercalcemia leads to polyuria and calcuria
-low phosphate due to increased renal excretion
-muscle weakness and east fatiagbilty (decrease entry of Na into the neurons)
-osteoblastic activity also increased leading to high secretions of alkaline phosphatase
What is secondary hyperparathyroidism?
high PTH levels occur as compensation for hypocalcemia not due to primary abnormalities of parathyroid glands
What are causes of secondary hyperparathyroidism?
vitamin D deficiency
chronic renal disease
-can not make vitamin D3
What does vitamin D deficiency lead to?
in children-rickets
in adults-osteomalacia
high PTH which causes bone resorption
What is primary hypoparathyroidism?
usually due to accidental surgical removal
-decreases plasma Ca levels
-increase membrane Na permeability leading to neuromuscular excitability and muscle spasms (tetany)
-spasms of laryngeal muscles obstruct respiration causing death unless appropriate treatment applied
