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PBL SEM 4 > CASE 9 > Flashcards

CASE 9 Flashcards

1
Q

THYROID

  • located _________ to the larynx on each side of and _________ to the trachea
  • composed of lots of follicles — follicles are lined with _______ epithelial cells that secrete into the interior of the follicles
  • the secretory fluid in the follicles is called colloid
  • the main component of colloid is _________
A
  • inferiorly
  • anteriorly
  • cuboidal
  • thyroglobulin
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2
Q

what does the thyroid secrete?

A

thyroxine (T4), triiodothyronine (T3), and calcitonin

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3
Q

what is thyroid secretion controlled by?

A

thyroid secreting hormone (TSH) from the anterior pituitary gland

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4
Q

what is iodide trapping?

A

the basal membrane of the thyroid actively pumps the iodide into the follicular cells of the thyroid gland through Na+/I= symporter

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5
Q

what stimulates iodide trapping?

A

TSH

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6
Q

what is the effect on iodide trapping when the thyroid gland becomes more active?

A

more iodide is actively transported into the follicle cell

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7
Q

what catalysed the oxidation of iodide ions?

A

peroxidase enzyme

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8
Q

what is iodide oxidised to?

A

iodine

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9
Q

where is peroxidase enzyme located?

A

either located in the apical membrane of the follicle cells or attached to it

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10
Q

what is the organification of thyroglobulin

A

the binding of iodine with the thyroglobulin molecule

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11
Q

what is tyrosine iodised to and then converted to?

A
  1. tyrosine is first iodised to monoiodotyrosine (MIT)
  2. MIT is then converted to diiodotyrosine (DIT)
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12
Q

what forms T3 and T4?

A

thyroxine = 2 coupled DIT molecules — T4. thyroxine remains part of the thyroglobulin molecule

triodothyronine (T3) = coupling of one MIT + one DIT — T3

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13
Q

effects of thyroid hormone on mitochondria

A

increase mitochondrial activity — increases the size and number of mitochondria. the total membrane SA of the mitochondria also increase in proportion to the increased metabolic rate — more ATP production and cellular function

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14
Q

what effect does TH have on ion active transport?

A

increases ion active transport — increases NaK ATPase activity

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15
Q

what growth does TH promote?

A
  • promote growth in growing children
  • promotes growth of brain during foetal development and first few years of life
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16
Q

what effect does TH have on cholesterol, phospholipids and triglycerides levels? effect of hypothyroidism?

A

lowers levels (even though TH increases FFAs)

not enough TH —> excess deposition of fat in the liver

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17
Q

vitamins and TH

A

increases need for vitamins (therefore vitamin def can occur when there is excess TH)

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18
Q

effect of TH on heart and blood flow

A

increases blood flow, cardiac output, HR, heart strength (arterial pressure remains normal) (SBP elevates in hyperthyroidism and diastolic pressure decreases)

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19
Q

hyper vs hypo thyroidism on GI motility

A

TH increases GI motility therefore:

hypothyroidism - constipation
hyperthyroidism - diarrhoea

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20
Q

where is thyrotropin releasing hormone (TRH) released from? where does it then go?

A
  • secreted by nerve endings in the median eminence of the hypothalamus
  • from the median eminence, the TRH is then transported to the anterior pituitary by the way of the hypothalamic-hypophysial portal blood
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21
Q

what does calcitonin do?

A

decreases plasma Ca conc

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22
Q

where is calcitonin made and secreted from?

A

C cells, lying in the interstital fluid between the follicles of the thyroid gland

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23
Q

what effect does increased plasma Ca conc have on calcitonin secretion?

A

increases calcitonin secretion

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24
Q

parathyroid hormone secretion is stimulated by what?

A

low Ca conc

25
how does calcitonin decrease blood Ca ion conc?
1. immediate effect — decrease the absorptive activities of osteoclasts thus shifting the balance in favour of deposition of calcium in the exchangeable bone calcium salts 2. prolonged effect — decrease the formation of new osteoclasts
26
how does parathyroid hormone (PTH) control extracellular calcium and phosphate concs?
by regulating: - intestinal reabsorption - renal excretion - exchange of these ions between the ECF and bone
27
what does excess action of the parathyroid gland cause?
excess PTH release - rapid absorption of Ca slats form the bones — hypercalcaemia in ECF
28
how does PTH increase Ca and phosphate absorption from the bone?
1. rapid phase — results from activation of osteocytes to promote calcium and phosphate absorption 2. slow phase — results from proliferation of the osteoclasts, followed by greatly increased osteoclast reabsorption of the bone itself
29
what is the most common cause of endogenous hyperthyroidism?
Grave’s dosease
30
Grave’s disease is characterised by what triad of clinical findings?
1. hyperthyroidism due to diffuse, hyper functional enlargement of the thyroid 2. infiltrative ophthalmopathy with resultant exophthalmos (protrusion f eyeball) 3. pretibial myxoedema
31
what antibodies are present in Grave’s disease?
TSH receptor
32
what is the most common cause of hypothyroidism in areas of the world where iodine levels are sufficient?
Hashimoto thyroiditis — THIS DISEASE DESCRIEBS PATIETNS WITH GOITRE AND INTENSE LYMPHOCYTIC INFILTRATION OF THE THYROID
33
what disease is characterised by the gradual thyroid failure due to autoimmune destruction of the thyroid?
hashimoto thyroiditis
34
what antibodies are present in hashimoto thyroiditis?
antibodies against thyroid peroxidase, thyroglobulin and TSH receptors
35
how does a goitre develop?
- low iodine levels - decreased synthesis and secretion of TH - compensatory increase in TSH - follicular cell hypertrophy and hyperplasia - growth and enlargement of thryoid gland (goitre)
36
where are the different types of B-receptors located?
B1 = mainly in heart and kidneys B2 = lungs, GIT, liver, uterus, vascular smooth muscle, skeletal muscle B3 = adipocytes
37
what does B1 stimulation by adrenaline/noradrenaline result in?
heart — increases cardiac conduction velocity and automaticity kidneys — renin release d
38
what does stimulation of B2 receptors cause?
smooth muscle relaxation/bronchodilation induces tremor in skeletal muscle increases glycogenolysis in liver and skeletal muscle
39
what does B3 stimulation cause?
lipolysis
40
what is an adverse effect of blockade by beta blockers at B1, especially at macula densa?
inhibits renin release — decreases release of aldosterone, causing hyponatraemia and hyperkalaemia
41
what are the effects on glucose levels by blockade of B2 receptors?
hypoglycaemia because B2 adrenoreceptors normally stimulate glycogenolysis (hepatic glycogen breakdown) and pancreatic release of glucagon
42
what is pronanolol?
non-selective B blocker
43
in the zona glomerulosa, early action of what enzyme steers away from sex steroid precursors to aldosterone or cortisol?
HSD3B2
44
what enzyme does the zona fasciculata contain for the production of cortisol?
CYP11B2
45
describe CYP17A1 enzyme
- in zona reticulosa - allows for the production of sex steroid precursors (androstenedione)
46
47
what is the ratio of production of T3:T4 ?
1:20 — lots more thyroxine
48
half life of T3 vs T4?
longer for T4 - 4 days T3 - a day
49
what is more of a long term measure?
TSH (similar to HbA1c)
50
subclinical hypothyroidism
TSH high and T4 normal
51
subclinical hyperthyroidism
TSH low and T4 normal
52
what would be seen if someone takes a load of thyroxine in one go?
high T4/3 and a normal TSH (takes longer)
53
what is sick euthyroid syndrome?
low TSH and T4 — common in hospital inpatient . abnormal thyroid levels in patients with non-thyroid related illnesses
54
what long term health effects can you get from hyperthyroidism?
atrial fibrillation, osteoporosis
55
another name for primary adrenal insufficiency
addisons disease
56
when does secondary adrenal insufficiency occur?
occurs when the pituitary gland doesn't make enough of the hormone ACTH
57
gad65 antibodies
The glutamic acid decarboxylase 65-kilodalton isoform (GAD65) antibody is a biomarker of autoimmune central nervous system (CNS) disorders and, more commonly, nonneurological autoimmune diseases. Type 1 diabetes, autoimmune thyroid disease, and pernicious anemia are the most frequent GAD65 autoimmune associations.
58
primary vs secondary hypoadrenalism
primary = lack of cortisol AND aldosterone secondary = normal aldosterone but deficient in cortisol (because don’t have any ACTH coming from pituitary gland)

PBL SEM 4 (50 decks)

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