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HHD 2 > Thyroid > Flashcards

Thyroid Flashcards

1
Q

The thyroid gland consists of two lobes connected by a _________.

A

isthmus

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2
Q

The thyroid gland is anterior to what structures?

A

larynx
trachea

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3
Q

What is the arterial supply for the thyroid gland?

A

superior thyroid artery (ECA)
Inferior thyroid artery (SC)

External carotid artery, subclavian artery

The thyroid is extremelt vascular

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4
Q

What vessels provide venous drainage to the thyroid gland?

A
  • superior and middle thyroid veins (IJV)
  • inferior thyroid vein (BCV)

Internal jugular vein, brachiocepahlic vein

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5
Q

What nerves provide autonomic supply to the thyroid gland?

A
  • sympathetic chain
  • parasympathetic - recurrent laryngeal nerve, superior laryngeal nerve
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6
Q

Structural units of the thyroid gland are referred to as __________.

A

follicles

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7
Q

What is a thyroid follicle?

A

they are simple epithelium enclosing a colloid filled cavity

colloid- mixture of microscopic particles that are suspended in another mixture

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8
Q

What structures surround the thyroid follicle?

A
  • blood vessels
  • connective tissue
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9
Q

The thyroid also contains scattered parafollicular cells (C-cells); what is their function?

A

secrete calcitonin

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10
Q

What cells surround the thyroid follicle and what is their function?

A
  • follicular cells
  • secrete thyroid hormones
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11
Q

What is the basic function of the thyroid gland?

A

regulates basal metabolic rate

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12
Q

List the functions of the thyroid gland

A
  • respiratory
  • regulation of digestion
  • cardiovascular- heart rate and heart structure
  • calcium regulation
  • catecholamine sensitivity (response to NA, A)
  • sexual function
  • metabolism- basal metabolic rate, heat generation (mitochondrial activity), macronutrient metabolism
  • growth- cell differentiation, bone maturation, nerve development, brain maturation in foetus

  • congenital hypothyroidism can lead to birth defects
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13
Q

The initial instruction for thyroid hormone synthesis comes from the __________. What hormone does it produce?

A
  • hypothalamus
  • thyroid releasing hormone (TRH)
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14
Q

What is the function of TRH?

A

stimulates the release of thyroid stimulating hormone (TSH) from the anterior pituitary gland

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15
Q

What is the function of TSH?

A

stimulates thyroid to produce thyroxine (T4) and triiodithyronine (T3) from follicular cells using iodine

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16
Q

What mechanism controls release of TRH/TSH from the hypothalamus and pituitary?

A

T3 and T4 have a negative feedback mechanism on hypothalamus and pituitary

More T3&T4 cause less TSH and TRH to be released from anterior pituitary and hypothalamus and vice versa

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17
Q

Briefly outline the synthesis of T3 and T4 hormones

A
  • follicular cells synthesise enzymes and thyroglobulin for the thyroid colloid
  • iodine is cotransported into the cell with Na+ and transported into the colloid
  • thyroglobulin then enters the colloid from the follicular cells and enzymes add iodine to thyroglobulin to make T3 and T4
  • thyroglobulin [modified with iodine] is then taken back into the follicular cell where intracellular enzymes seperate T3 and T4 from the protein
  • free T3 and T4 enter circulation
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18
Q

What are the levels of TSH, T3 and T4 in a euthyroid ?

A
  • normal TSH
  • normal T3
  • normal T4
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19
Q

What are the levels of TSH, T3 and T4 in subclinical hypothyroidism ?

A
  • high TSH
  • normal T3
  • normal T4

this is an early warning sign for hypothyroidism; low thyroid has been detected so hypothalamic-pituitary axis aims to compensates and secretes more TSH so normal levels of thyroid hormones are produced

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20
Q

What are the levels of TSH, T3 and T4 in hypothyroidism ?

A
  • high TSH
  • low T3
  • low T4
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21
Q

What are the levels of TSH, T3 and T4 in subclinical hyperthyroidism ?

A
  • low TSH
  • normal T3
  • normal T4

less TSH released as higher than normal levels of thyroid hormone detected

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22
Q

What are the levels of TSH, T3 and T4 in hyperthyroidism?

A
  • low TSH
  • high T3
  • high T4
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23
Q

List primary causes of hypothyroidism

A
  • hashimotos autoimmune thyroiditis
  • iodine deficiency (developing world)
  • postpartum thyroiditis
  • iatrogenic (medically caused)
  • drugs amiodarone and lithium
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24
Q

Outline some central causes of hypothyroidism

A
  • pituitary lesions
  • infiltrative diseases- massive lymphocyte infiltration in the thyroid
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25
Q

What is the most common cause of hypothyroidism in the UK?

A

hashimotos disease

26
Q

What is the presentation of hashimotos diseases? Why is this?

A

Goitre- swelling in the neck/ swollen thyroid gland
Lymphocyte infiltration in thyroid endemic goitre

27
Q

What are the main types of hypothyroidism?

A
  • primary
  • central
  • congenital
28
Q

Briefly describe the effect of amiodarone on the thyroid gland

A

usually causes a hyperthyroid effect before a hypothyroid effect because of the damage and scarring caused to the thyroid

29
Q

What are the levels of TSH, T3 and T4 in central hypothyroidism ?

A
  • low TSH
  • low T3
  • low T4

disorder to pituitary, hypothalamus or hypothalamic pituitary portal circulation

Remember central hypothyroidism involves lesions to the pituitary

30
Q

What is the presentation of hypothyroidism ?

A
  • weakness
  • lethargy
  • sensitive to cold
  • constipation
  • weight gain
  • depression
  • menstrual irregulariy
  • dry skin
  • eyelid/facial oedema
  • myxoedema- thickening of skin
  • macroglossia- swollen tongue
  • bradycardia
31
Q

A serum sample for a hypothyroidism will confirm … (levels of hormones)

A
  • high TSH
  • low T3&4
32
Q

How is hypothyroidism managed?

A
  • levothyroxine
  • regular monitoring of levels- people respond to thyroid replacement differently
33
Q

List the causes of hyperthyroidism

A
  • graves disease (autoimmune)
  • toxic multi-modular goitre
  • thyroid adenoma (single nodule)
  • iatrogenic
  • amiodarone
  • post-partum
34
Q

What is the presentation of hyperthyroidism?

A
  • heat intolerance
  • sweating
  • weight loss
  • anxiety
  • palpitations
  • fine tremor
  • tachycardia (atrial fibrillation)
  • pretibial myxoedema
  • orbitopathy- lid retraction, exopthalamus, chemosis, EOM involvment, sight loss

Lid retraction- thyroid gland stimulating mullers muscle; you should not see the whites of the eyes above the iris; this is an indication of lid retraction

EOM -extraocular muscle

35
Q

What is myxoedema?

A

this is the presence of an increased ground substance in subcutaneous tissue which leads to thickening of the skin

36
Q

How is hyperthyroidism diagnosed?

A
  • serum samples; low TSH, high T3&4; presence of TSH receptor antibodies
  • thyroid ultrasound
  • radioactive iodine uptake
37
Q

What is graves disease ?

A
  • autoimmune condition
  • antibodies that mimic TSH and bind to TSH receptors on the thyroid gland are produced
38
Q

What is the treatment of hyperthyroidism?

A
  • anti-thyroid drugs such as carbimazole
  • symptomatic managment ; propanolol - beta blocker for tachycardia
  • radioactive iodine- taken up by the gland and damage the gland
  • methylprednisolone for orbitopathy
  • surgical resection
39
Q

What is the MOA of carbimazole?

A
  • interferes with cascade of enzyme that synthesise thyroid hormones
40
Q

Overproduction of hormones in endocrine glands is usually due to…

A
  • adenoma (benign)
  • adenocarcinoma (malignant)
  • hyperplasia
41
Q

What are the dental considerations for hyperthyroidism?

A
  • increased susceptibility to caries
  • periodontal disease
  • maxillary or mandibular osteoporosis (mobilisation of calcium in the bone)
  • accelerated dental eruption
  • burning mouth syndrome
  • increased incidence of sjogrens syndrome (remember autoimmune diseases travel in packs)
42
Q

What are some dental considerations of congenital hypothyroidism?

A
  • macroglossia
  • thick lips
  • malocclusion
  • delayed eruption of teeth
43
Q

What are some long term dental considerations for hypothyroidism?

A
  • impaction of second molars due to lack of space for proper eruption (due to incomplete resorption)
  • dysgeusia - foul, salty, rancid or metallic taste sensation
  • poor wound healing
44
Q

How are thyroid cancers mostly presented? How is it ususally detected?

A
  • asymptomatic thyroid nodule
  • palpitation or ultrasound in a woman in her 30s or 40s
45
Q

What is the diagnostic test for thyroid cancers?

A
  • fine needle aspiration
46
Q

What is the treatment for thyroid cancers?

A

total thyroidectomy followd by radioactive iodine ablation and TSH suppression

47
Q

What are the 4 types of malignan thyroid cancers?

A

Papillary
Follicular
Anaplastic
Medullary

48
Q

80% of thyroid cancer cases are papillary, what is the prognosis for these types of cancers?

A

excellent prognosis

49
Q

What kind of malignant thyroid cancer has the worst prognosis?

A

Anaplastic

50
Q

What kind of malignant thyroid cancer is associated with multiple endocrine neoplasia?

A

Medullary

51
Q

Medullary thyroid cancer is a cancer of what cells?

A

Parafollicular cells

52
Q

What are multiple endocrine neoplasias?

A

hereditary tumour syndromes with distinct patterns of organ development

53
Q

What is the pattern of inheritance for multiple endocrine neoplasia (MEN)?

A

autosomal dominant mutations (inherited or sporadic)

54
Q

What are the two types of MEN syndromes?

A

MEN1
MEN2

55
Q

90% of people with MEN1 syndromes will develop …

A

primary hyperthyroidism

56
Q

30-70% of people with MEN1 syndromes will develop…

A

pancreatic neuroendocrine tumours

57
Q

10% of people with MEN1 syndromes will develop …

A

pituitary adenomas

58
Q

> 90% of people with MEN2 syndrome will develop…

A

medullary thyroid tumour (parafollicular dells)

59
Q

50% of people with MEN2 syndrome will develop…

A

phaeochromocytoma

60
Q

30% of people with MEN2 syndrome will develop…

A

parathyroid adenoma

61
Q

What gene has been implicated in MEN2 syndromes?

A

RET- oncogene (if given the chance will predipose individual to a malignancy)

HHD 2 (37 decks)

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