ENDO III- Thyroid and Parathyroid hormones Flashcards
1
Q
what are the percentages of active hormones secreted by the thyroid gland
A
93% T4 and 7% T3
2
Q
what are the names for T4 and T3
A
T4: thyroxine
T3: triidothyronine
3
Q
which is more potent T3 or T4
A
T3
4
Q
what do thyroid hormones do
A
impact metabolism and growth/development
- permissive action on catecholamines
5
Q
what is thyroglobulin stored in
A
colloid follicle
6
Q
what do parafollicular cells secrete
A
calcitonin
7
Q
what does calcitonin do
A
decreases plasma calcium
8
Q
what molecule is required for thyroid hormone synthesis
A
iodine
9
Q
what is on the blood side of the follicular cell
A
sodium/ iodide symporter
10
Q
what gets iodine into colloid
A
pendrin
11
Q
what does peroxidase do
A
makes thyroid hormones
12
Q
what is located on the apical membrane of the follicular cell
A
Cl-/I- exchanger AKA pendrin
13
Q
where are T3 and T4 produced and what are they complexed with
A
produced in the colloid complexed with thyroglobulin
14
Q
what is the precursor for T3 and T4
A
tyrosine
15
Q
how is T3 and T4 secreted into the blood
A
-colloid is internalized by endocytosis
-the 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
16
Q
what do T3 and T4 bind with for transport
A
plasma proteins: TBG,TTR, and albumin
17
Q
which has a longer half life T3 or T4
A
T4
18
Q
what dictates half life
A
the strength of binding to the transport protein
19
Q
is T3 or T4 secreted more
A
T4
20
Q
how do target cells make active T3
A
by using enzymes called deiodinases that remove and iodine from T4
21
Q
what do the 3 different deiodinases contain
A
rare AA called selenocysteine with selenium in place of sulfur
22
Q
what conditions inhibit deiodinases
A
selenium deficiency, burns, trauma, advanced cancer, cirrhosis, chronic kidney disease, MI, febrile states, fasting, stress
23
Q
what could the inhibition of deiodinases lead to
A
hypothyroidism
24
Q
which actions occur sooner and when is max activity
A
T3, at 2-3 days
25
which has a longer duration of action
T4
26
where is T4 converted into T3
anterior pituitary and hypothalamus
27
what effect does thyroid hormones have on the cardiovascular system
-increased CO
-increased blood flow
- increase HR
- Increased heart strength
-increased respiration
-increased beta receptor expression
28
what effect does thyroid hormones have on metabolism
-increased glucose absorption
-increased gluconeogenesis
-increased fat metabolism (lipolysis)
-increased protein catabolism and synthesis
-increased BMR!!!
-increased mitochondria
-increased sodium potassium ATPase
-increased O2 consumption
29
what is the control of thyroid hormone secretion
negative feedback mainly at the level of the anterior pituitary gland
30
what hormone is responsible for most of the negative feedback of thyroid hormones
T4
31
what is the main circulating form of the thyroid hormones
T4
32
when does TSH secretion peak
midnight
33
describe TSH secretion
pulsatile and tonic
34
how do thyroid hormones stimulate carbohydrate metabolism
-causes uptake of glucose by cells
- enhances glycolysis and gluconeogenesis
- increases rate of CHO absorption from GI tract
35
how do thyroid hormones stimulate fat metabolism
-increases lipid mobilization and oxidation of fatty acids by cells
- required to convert beta carotene to vitamin A
-decreases circulating cholesterol levels
36
what thyroid disorder is hyperlipidemia associated with
hypothyroidism
37
how do thyroid hormones effect the nervous system
-normal development of NS
- impacts reflex time
-muscle tremors due to increased reactivity of neuronal synapses
-feeling of tiredness but difficulty sleeping
-anxiety, worry, paranoia
38
how do thyroid hormones effect the endocrine system
-increased glucose consumption results in increased insulin secretion to maintain blood glucose levels
-activation of bone formation causes a need for increased PTH secretion
- causes increased inactivation of glucocorticoids which leads to more ACTH release
39
how do thyroid hormones affect the cardiovascular systrm
-increased expression of beta adrenergic receptors
-increased blood flow, heart rate, and heart contractility
40
how do thyroid hormones affect the GI system
-increased appetite and food intake
- increased rate of secretion and motility of GI tract
41
what is goiter
enlarged thyroid that does not indicate functional status
42
what is euthyroidism
normal thyroid
43
what can goiter be caused by
excessive amounts of TSH secretion,, high TSH stimulates thyroid to secrete large amounts of thyroglobulin colloid into follicles resulting in gland enlargment
44
what is the most common form of hyperthyroidism
graves disease
45
besides graves disease how else can hyperthyroidism occur
a thyroid adenoma
46
what is graves disease
antibodies to TSH receptor called thyroid stimulating immunoglobulins (TSIs) stimulate the thyroid gland to excess
47
how do TSI antibodies affect the thyroid gland compared to TSH
TSI antibodies have prolonged stimulating effect on thyroid gland lasting longer
48
what do high levels of thyroid hormone secretion caused by TSI do
suppress anterior pituitary TSH secretion
49
what type of endocrine disorder is graves disease
primary
50
what are symptoms of hyperthyroidism
-exopthalmos
-fine hair
-nervousness
-restlessness
-emotional instability
-insomnia
-increased apatite
-fine tremor
- pretibial myxedma
51
how is hyperthyroid treated
radioactive iodine thyroid ablation or antithyroid drugs. rarely surgery
52
what medication is given in hyperthyroidism while awaiting resolution
propanolol- beta blocker
53
what is L-thyroxine used for in hyperthyroidism
to prevent hypothyroidism in patients who have undergone ablation or surgery
54
what are the oral symptoms of hyperthyroidism
-burning mouth syndrome
-gum disease
-excessive salivation
- weakening of mandible
- increased caries risk
55
what is a thyroid storm
elevated thyroid hormone with stressful events or serious illness
56
what are the symptoms of a thyroid storm
fever, tachycardia, elevated BP, nausea, vomiting, diarrhea, breathing problems
57
what is contraindicated in patients with hyperthyroidism
administration of epinephrine
58
what is hashimotos thyroiditis
autoimmune reaction against thyroid gland destroys gland
59
what is the most common cause of hypothyroidism
hashimotos thyroiditis
60
what is the first symptom of hashimotos
thyroiditis or thyroid inflammation
61
what does thyroid inflammation lead to in hashimotos
fibrosis of thyroid resulting in decreased secretion of thyroid hormone
62
what does goiter vs no goiter mean in hypothyroid states
goiter: iodine deficiency
no goiter: TSH deficiency
63
is hypothyroidism due to iodine deficiency a primary or secondary endocrine disorder
primary
64
is hypothyroidism due to TSH deficiency a primary or secondary endocrine disorder
secondary
65
is goiter a primary or secondary endocrine disorder
primary
66
what are the symptoms of hypothyroidism
-coarse, dry brittle hair
-loss of lateral eyebrows
-lethargy and impaired memory
- cold intolerance
-constipation
-weight gain
67
when is myxedema seen
in severely hypothyroid patients
68
what causes myxedema
increased quantities of hyaluronic acid and chondroitin sulfate bound with protein plus water accumulate in skin
69
what are other characteristics of hypothyrodism
-low BMR
-low mental capacity
-low body temp
-low appetite
-low HR
-low RR
-low BP
-weight gain
-increased cholesterol and blood lipids
70
what does the face look like with myxedema
dull,expressionless face with puffiness of eyelids. skin appears swollen, cool, waxy, dry, coarse
71
what is cretinism
physical and mental retardation due to either congenital absence of thyroid gland or iodine deficient diet
72
what is more inibited in cretinism: skeletal growth or soft tissue
skeletal growth
73
what are the oral manifestations of hypothyroidism
-macroglossia
-dysgeusia
-delayed tooth eruption
-poor wound healing and increased risk of infection due to decreased activity of fibroblasts
-increased periodontal disease
-salivary gland enlargement
74
where the bodys phosphate stored
85% in bones, 14-15% in cells, less than 1% in EC fluid
75
where is calcium stored
-0.1% in EC fluid
-1% in cells
and rest in bones
76
what does too low of calcium result in
neuronal hyperexcitability like carpal spasm
77
what does too high of calcium result in
neuronal depression
78
what are the control points for calcium and phosphate
-absorption- via intestines
- excretion- via urine and feces
- temporary storage- via bones as hydroxyapatite
79
what hormones regulate plasma calcium
-PTH
-calcitriol
-calcitonin
80
what does PTH do
-increases calcium
-decreases phosphate
-mobilizes calcium from bone
-increases renal absorption of calcium
-increases intestinal absorption of calcium
81
what does calcitriol do
increase plasma calcium and increase phosphate
82
what is the primary hormone that enhances intenstinal absorption of calcium
calcitriol
83
what does calcitonin do
-decreases calcium
-decreases phosphate
84
what is bone formation stimulated by
calcitonin, insulin, GH, IGF1, estrogen and testosterone
85
what effect does vitamin D and PTH have on bone matrix
stimulates bone matrix resorption
86
how do vitamin D and PTH stimulate bone matrix resorption
stimulates osteoclasts through RANKL
87
what effect does calcitonin have on bone matrix
stimulates deposition
88
how does calcitonin stimulate deposition
uses more OPG and inhibits osteoclast
89
what are the risk factors for osteoporosis
vitamin D deficiency, secondary hyperparaythyroidism, inadequate calcium intake, glucocorticoid medications, reduced physical activity, estrogen deficiency
90
what are the treatments for osteoporosis
-exercise
-PT
-estrogen
- calcium
-vitamin D
91
what is PTH secreted by
chief cells
92
what does PTH do
-increases plasma calcium by increasing intestinal absorption, decreasing renal excretion and increasing bone resorption
- decreased plasma phosphates by increased renal excretion
93
what does decreased ECF Ca2+ concentration cause
increased rate of PTH secretion hypertrophy of parathyroid gland seen in pregnancy and rickets
94
what does increased ECF Ca2+ cause
-decreased activity of Parathyroid gland
-decreased size of parathyroid gland caused by increased vitamin D intake
95
how does PTH increase plasma calcium
-bone resorption
-reabsorption of calcium by renal tubules which reduced excretion
-converts to vitamin D to cause intestinal absorption
96
how does PTH decrease plasma phosphate
decreased reabsorption by renal tubules leading to increased urinary excretion
97
what organs are targets of PTH
kidneys, bone, intestine
98
what is a precursor for calcitriol
vitamin D
99
where and how long is vitamin D3 stored
in the liver for months
100
how is calcitriol synthesized
stored in liver, activated in kidney by PTH where it results in intestinal absorption of calcium
101
what is the main effect of calcitriol
absoprtion of calcium and phosphate
102
how does calcitonin lower plasma calcium
by decreasing activity of osteoclasts, thus decreasing bone resorption
103
does calcitonin have major control over calcium
NO
104
what is primary hyperparathyroidism due to
parathyroid gland tumor
105
what does extreme osteoclastic activity in primary hyperparathyroidism cause
cystic bone disease called osteitis fibrosa cystica
106
what happens in osteitis fibrosa cystica
-hypercalcemia leads to polyuria and calcuria
- low phosphate due to increased renal excretion
- muscle weakness and easy fatigability
- osteoblastic activity also increased leading to high secretion of alkaline phosphatase
107
what are the primary signs and symptoms of primary hyperparathyroidism
- kidney stones and polyuria
-psychic moans
-abdominal groans
- osteitis fibrosa in bones
108
what is secondary hyperparathyroidism
High PTH levels occur as compensation for hypocalcemia not due to primary abnormality of parathyroid glands
109
what are the causes of hypocalcemi
-vitamin D deficiency
- chronic renal disease - cannot make vitamin D3
110
what does vitamin D deficiency cause
rickets in childre, osteomalacia in adults, and high PTH which causes bone resorption
111
what is primary hypoparathyroidism caused mainly by
accidental surgical parathyroid gland removal
112
what does parathyroid gland removal do to calcium levels
decreases plasma Ca levels from 10 mg/dl to 6-7 mg/dl
113
what does hypocalcemia lead to
increases membrane Na+ permeability leading to neuromuscular excitability and muscle spasms and tetany
