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pathophysiology 4802 > Thyroid Disease > Flashcards

Thyroid Disease Flashcards

1
Q

is this another word for hyperthyroidism or hypothyroidism: thyrotoxicosis

A

hyperthyroidism

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2
Q

is this another word for hyperthyroidism or hypothyroidism: myxedema

A

hypothyroidism

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3
Q

the thyroid gland synthesizes these two hormones that regulate the body’s metabolic rate

A

thyroxine (T4) (prohormone) and triiodothyronine (T3) (active hormone)

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4
Q

explain the basic anatomy of the thyroid gland

A
  • firm, reddish brown, smooth gland
  • has two lateral lobes (right and left)
  • has a pyramidal lobe that is centrally over the trachea
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5
Q

the thyroid gland consists of many closely placed acini called _________ each surrounded by capillaries and stroma. its function is to trap dietary iodine and transport it into the colloid along with enzyme thyroidal peroxidase

A

follicles

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6
Q

each follicle in the thyroid gland is roughly spherical, lined by a single layer of __________ epithelial cells

A

cuboidal

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7
Q

the follice is filled with _________ which is a proteinaceous material composed mainly of thyroglobulin and stored thyroid hormones

A

colloid

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8
Q

does this describe an active or inactive thyroid gland:
- follicles are large
- lining cells are flat
- colloid is abundant

A

inactive thyroid gland

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9
Q

does this describe an active or inactive thyroid gland:
- follicles are small
- lining cells are cuboidal or columnar
- colloid is scanty
- edges are scalloped forming reabsorption lacunae

A

active thyroid gland

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10
Q

scattered between follicles are _______ which secrete calcitonin (a hormone that inhibits bone resorption)

A

parafollicular cells (C cells)

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11
Q

this glycoprotein is synthesized by the thyroid follicular cells, and contains many tyrosine residues

A

thyroglobulin

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12
Q

true or false: the thyroid hormones remain attached to thyroglobulin until stimulated by TSH

A

true

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13
Q

true or false: released thyroid hormones (T3 and T4) are water soluble and diffuse from the follicle into circulation

A

false - they are lipid soluble

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14
Q

true or false: more of the thyroid hormone is in the form of T3 than T4

A

false - 90% of thyroid hormone is in the form of T4 whereas only 10% is in the form of T3 (T3 = active form)

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15
Q

this form of iodine is absorbed and taken up by the thyroid

A

iodide

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16
Q

iodide in the thyroid cell is oxidized to iodine which is catalyzed by what enzyme

A

thyroidal peroxidase

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17
Q

during thyroid hormone synthesis, the iodine enters the colloid and is rapidly bound at the 3 position to tyrosine molecules attached to thyroglobulin forming _________

A

moniiodotyrosine (MIT)

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18
Q

during thyroid hormone synthesis, MIT is iodinated at the 5 position forming __________

A

diiodotyrosine (DIT)

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19
Q

during thyroid hormone synthesis, two DIT molecule then condense in an oxidative process catalyzed by thyroperoxidase to form _________

A

thyroxine (T4)

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20
Q

both T3 and T4 are bound to plasma proteins such as

A
  • albumin
  • transthyretin
  • thyroxine-binding globulin (TBG)
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21
Q

does the free (unbound) or bound T4 and T3 inhibit pituitary TSH secretion

A

free/unbound

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22
Q

which hormone (T3 or T4) has a longer half-life?

A

T4 has a long half-life (about 6-7 days)
T3 has a shorter half life (about 24 hours)

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23
Q

Both T3 and T4 are metabolized in the liver, kidneys and many other tissues. they are conjugated into glucoronides in the liver and excreted into the ____

A

bile

24
Q

this thyroid hormone binds to its receptor and exerts its actions, mediated through alteration in gene transcription

A

T3

25
Q

this thyroid hormone is acted upon by cellular enzymes that cleave one of the iodine molecules to form the active form

A

T4

26
Q

thyroid hormone secretion is stimulated by pituitary __________

A

thyroid stimulating hormone (TSH)/thyrotropin

27
Q

Pituitary TSH secretion is stimulated by ________, a tripeptide secreted by the hypothalamus

A

thyrotropin releasing hormone (TRH)

28
Q

true or false: TSH secretion is inhibited by stress, dopamine and somatostatin

A

true

29
Q

true or false: free T4 and T3 act as a positive feedback loop to the anterior pituitary

A

false - negative feedback loop: more free T4 and T3 inhibits TSH release therefore less T4 and T3 released

30
Q

true or false: most thyroid diseases probably involves an autoimmune process

A

true

31
Q

transient hyperthyroidism is occasionally observed in patients with lymphocytic or granulomatous ___________ or ___________. in such cases, the hyperthyroidism is due to destruction of the thyroid with the release of stored hormone

A

subacute thyroiditis or Hasimoto disease

32
Q

what are some environmental factors that may cause hyperthyroidism

A
  • infection
  • excessive iodide ingestion
  • amiodarone
33
Q

this disease is characterized by thyroid follicular cell hyperfunction with increased secretion of T4 and T3

A

grave’s disease

34
Q

this disease is characterized by thyroid follicular cell destruction with release of T4 and T3

A

Hashimoto thyroiditis

35
Q

does this describe primary, secondary , tertiary or ectopic hyperthyroidism
- thyroid gland affected
- elevated levels of T3 and T4
- decreased levels of TRH and TSH

A

primary hyperthyroidism
*note: if thyroid hormones are affected, thyroid gland is the culprit

36
Q

does this describe primary, secondary , tertiary or ectopic hyperthyroidism
- hypophysis affected
- elevated levels of TSH
- T3 and T4 are also high, TRH is inhibited

A

secondary hyperthyroidism

37
Q

does this describe primary, secondary , tertiary or ectopic hyperthyroidism
- the hypothalamus is affected thus TRH levels are affected

A

tertiary hyperthyroidism

38
Q

does this describe primary, secondary , tertiary or ectopic hyperthyroidism
- a struma ovarii present (tumor in ovary that contains thyroid tissue)

A

ectopic hyperthyroidism

39
Q

this disease is the most common cause of hyperthyroidism among individuals in their third and fourth decades but can occur at any age. this disease is familial. a genetic contribution to the development of this disease is suggested by the finding of much higher concordance rates in monozygotic same-sex twin pairs than dizygotic. is associated with HLA-B8 and HLA-DR3 (in caucasians), HLA-Bw46 and HLA-B5 in (Asians) and HLA-B17 (in blacks), therefore other autoimmune disorders often accompany this disease. it is also more common in women

A

Graves disease

40
Q

the serum of more than 90% of patients with Grave’s disease contains _____ antibody, directed against the TSH receptor site in the thyroid follicular epithelial membrane.

A

TSH-R [stim]

41
Q

what is the cause of the producing of TSH-R [stim] antibody?

A

unknown! could be molecular mimicry or suppressor T lymphocyte defect

42
Q

a defect in supressor T lymphocytes allows helper T lymphocytes to stimulate B lymphocytes to synthesize __________

A

thyroid antibodies (such as TSH-R[stim] Ab

43
Q

______ is the driving force for thyrotoxicosis

A

TSH-R [stim] Ab or TSI (same thing)

44
Q

inflammation of the orbital muscles (which is seen as bulging of the eyes) may be due to the sensitization of _________

A

cytotoxic T lymphocytes

45
Q

what are some clinical manifestations (signs and symptoms) of Hyperthyroidism

A
  • changes in behaviour (e.g. insomnia, restlessness, palpitations, heat intolerance, sweating, etc.
  • increased appetite and dietary intake but paradoxical weight loss
  • changes in menstrual cycle
46
Q

what are some clinical manifestations (signs and symptoms) of Graves disease

A
  • thyromegaly (increased size of thyroid gland)
  • exophthalmos (bulging of eye)
  • widening of the palpebral fissure resulting in exposed sclera (cannot close eyelids all the way)
  • vision changes (blindness, photophobia)
47
Q

untreated hyperthyroidism may decompensated into a state called __________, where excessive amounts go thyroid hormones are acutely released. patients have tachycardia, fever, agitation, N/V/D, psychosis, etc. could be caused by surgical emergency, infection, etc. should be treated aggressively as mortality rate is high

A

thyroid storm

48
Q

this is characterized by abnormally low serum T4 and T3 levels. the serum TSH level is elevated, as there is insufficient hormone available to inhibit the secretion of TSH.

A

hypothyroidism

49
Q

if TSH levels are elevated in hypothyroidism, this will cause thyroid cells to secrete large amounts of thyroglobulin which leads to a _______

A

goiter

50
Q

what are some causes of hypothyroidism

A
  • most common: Hashimoto disease
  • lymphocytic thyroiditis
  • surgical removal of thyroid
  • iodine deficiency
51
Q

_____________ is caused by defects in TSH production which can result from
- severe head trauma
- cranial neoplasms
- brain infections
- cranial irradiation
- neurosurgical procedures

A

secondary hypothyroidism (rare)

52
Q

what are some clinical manifestations (signs and symptoms) of hypothyroidism in infants

A
  • routine screening is often mandatory
  • dull appearance
  • thick protuberant tongue and lips (makes it hard for baby to latch for feeding)
  • prolonged neonatal jaundice
  • poor muscle tone
  • bradycardia
  • umbilical hernia
  • hoarse cry
53
Q

what are some clinical manfiestaiotns (signs and symptoms) of hypothyroidism in children/adults

A
  • decreased basal metabolic rate
  • weakness, lethargy, cold intolerance, decreased appetite
  • bradycardia
  • mild/moderate weight gain
  • elevated serum cholesterol and TGs
  • enlarged thyroid, dry skin, constipation
  • depression, difficulties with concentration/memory
  • menstrual irregularity
54
Q

edema due to accumulation of glycosaminoglycans in the interstitial spaces describes ___________-

A

hypothyroidism

55
Q

iodine deficiency is the most common cause of ________

A

goiter

pathophysiology 4802 (16 decks)

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