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Endocrine and reproductive system > Thyroid function and dysfunction > Flashcards

Thyroid function and dysfunction Flashcards

1
Q

Which two hormones are released by the thyroid?

A

T3 and T4

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2
Q

How does hypothalamus communicate with anterior pituitary?

A

TRH

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3
Q

How does anterior pituitary communicate with thyroid?

A

TSH

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4
Q

Which two compounds form basis of T3 and T4?

A

Tyrosine and iodine

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5
Q

What does colloid do?

A

Production of T3/T4

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6
Q

How are T3/T4 made?

A 
Thyroglobulin made from follicular cells
I- and Na+ move into cell (co-transport)
I- trapped
TPO converts to iodine by H2O2
Binds to tyrosine 
Forms MIT and DIT
2x DIT makes T4
DIT and MIT makes T3
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7
Q

What does pendrin do?

A

Pushes iodine into colloid

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8
Q

What does thyroid hormone do?

A

Increases metabolic activity

Activates via DNA transcription

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9
Q

Half life of T3

A

1 day

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10
Q

Half life of T4

A

7 days

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11
Q

Why is more T4 made than T3?

A

T4 converted to T3

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12
Q

What does TSH do to make T3 and T4?

A

Stimulates symporter, thyroglobulin synthesis and exocytosis

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13
Q

Thyroid impact on gene expression in nucleus

A

Stimulates nuclear receptors to activate DNA transcription, receptors are normally occupied by inhibitory repressors which are displaced by T3 to start activation

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14
Q

Thyroid impact on gene expression in mitochondria

A

Direct action to increase oxidative phosphorylation, stimulates mitochondrial DNA transcription

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15
Q

Thyroid impact on cell membrane in mitochondria

A

GPCR (Gq) = stimulates nuclear DNA transcription

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16
Q

Action of thyroid hormones

A 
Enhances basal metabolic rate 
Increases cardiac muscle activity 
Increases Sympathetic NS activity 
Protein synthesis
Activates GH
17
Q

Symptoms of hypothyroidism

A
  • Weight gain
  • Under-active thyroid:
  • Slowed metabolic rate, reduced oxygen consumption, reduced protein synthesis
  • Symptoms:
  • Lethargy
  • Weight gain
  • Cold intolerance
  • Bradycardia/hypotension
  • Slow reflexes and speech
  • Dry skin/thinning hair
  • Mucopolysaccharide deposits (myxoedema)
  • Adult screening not done routinely
  • Outer third of eyebrow lost
18
Q

TSH, T3 and T4 for hypothyroidism

A

TSH increased, T3 and T4 decreased

19
Q

Causes of underachieve thyroid

A

Surgery
Anterior pituitary damage - tumour/surgery
Autoimmune - Hashimoto
Iodine deficiency

20
Q

What is Hashimoto’s disease?

A

Normal immune tolerance falls
CD4+ lymphocytes recruit B cells and CD8+ cells to thyroid
Anti-TPO ABs and anti-thyroid cytotoxic T cells result in follicular destruction

21
Q

Causes of congenital hypothyroidism

A

Iodine deficiency
Developmental failure
Genetic defects

22
Q

Symptoms of congenital hypothyroidism

A

Coarse appearance, floppy, mental retardation, short stature

23
Q

Symptoms of hyperthyroidism

A

Weight loss, heat intolerance, tremor, tachycardia, muscle weakness

24
Q

What is exophthalmos?

A

Inflammation behind eyes

25
Q

Causes of hyperthyroidism

A

TSH secreting tumour on ant. pituitary
Autoimmune (Grave’s or early Hashimoto)
Adenomas

26
Q

What is Grave’s disease?

A

Normal immune balance disrupted, anti-TSH receptor ABs generated that mimic TSH and stimulate receptor by binding to it

27
Q

Summary of Hashimoto

A

Anti TPO antibodies
Impaired thyroid hormone synthesis
Hypothyroidism
Low T3/4 and high TSH

28
Q

Summary of Grave’s disease

A

Anti TSH receptor
Binds to receptor and mimics TSH
Hyperthyroidism
High T3/4, low TSH

29
Q

Papillary thyroid cancer

A

Affects papillary cells
Slow growing
Spread to lymph nodes
Good outcome

30
Q

Follicular thyroid cancer

A

Affects follicle cells
Spreads to lungs/bones
Good outcome with surgery and iodine

31
Q

Medullary thyroid cancer

A 
Affects c cells (calcitonin)
Aggressive
Distant spread
Radical surgery needed
Fair outcome
32
Q

Anaplastic thyroid cancer

A 
Affects undifferentiated cells
Very aggressive 
Invades airway 
Treatments are minimally effective 
Poor outcome

Endocrine and reproductive system (25 decks)

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