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RACP Written 2018 > Endocrine - Hyper and Hypo Thyroidism > Flashcards

Endocrine - Hyper and Hypo Thyroidism Flashcards

1
Q

Thyroid Physiology

- embryology of the thyoroid?

A

Median ENDODERM downgrowth from BASE OF TONGUE and travels caudally with heart.

Thyroid gland duct breaks down by week 5-6

Enlargement from 4th brachial pouch

Colloid present by week 10
Thyroid functional by week 11-12

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2
Q

Thyroid Physiology

- anatomy of the thyroid?

A

Isthmus is just in front of trachea, just BELOW CRICOID CARTILAGE

Recurrent laryngeal nerve runs BETWEEN trachea and oesophagus

Pyramidal lobe (in 80%) is remnant of thyroglossal duct

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3
Q

Thyroid Physiology

- How does thyroid hormone provide negative feedback?

A

Thyroid hormone gives negative feedback via Thyroid Hormone Receptor Beta2
–> inhibits TSH and TRH

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4
Q

Thyroid Physiology

- Other than thyroid hormone what other suppressors of TSH?

A

Dopamine
Glucocorticoids
Somatostatin

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5
Q

Thyroid Physiology

- How is iodide uptaken?

A

Iodide uptake on basolateral membrane via NIS on follicular cells.
NIS is ALSO on salivary cells, placenta and lactating breasts
–> NIS is STIMULATED by low iodide levels
–> NIS is INHIBITED by high iodide levels (=Wolf-Chykoff Effect)

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6
Q

Thyroid Physiology

- What is NIS?

A

NIS is the basolateral channel on follicular thyroid cells via which iodide is uptaken.

NIS is ALSO on salivary cells, placenta and lactating breasts

  • -> NIS is STIMULATED by low iodide levels
  • -> NIS is INHIBITED by high iodide levels (=Wolf-Chykoff Effect)
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7
Q

Thyroid Physiology

- How does the iodide get into the follicular lumen of follicular thyroid cells?

A

Via PENDRIN transporter on apical membrane

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8
Q

Thyroid Physiology

- What happens to iodide once the iodide is in the follicular lumen?

A

Iodide is oxidised by TPO and HYDROGEN PEROXIDE

It is the bound to TYROSINE RESIDUES

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9
Q

Thyroid Physiology

- How does T3 and T4 form?

A

Iodised Tg is taken back into the cell and processed in lysosomes to form T3 and T4
DIT + DIT = T4
DIT + MIT = T3

Uncoupled tyrosine residues are MIT and DIT and these get recycled

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10
Q

Thyroid Physiology

- What combinations for DIT and MIT for thyroid hormones?

A

DIT + DIT = T4
DIT + MIT = T3

Uncoupled tyrosine residues are MIT and DIT and these get recycled

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11
Q

Thyroid Physiology

- How is thyroid hormone transported in blood?

A

Thyroid Binding Globulin (TBG) binds most T3/T4 but ONLY THE FREE HORMONE IS ACTIVE

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12
Q

Thyroid Physiology

- What creates high and low levels of TBG?

A

High TBG: pregnancy and OCP

Low TBG: liver failure and steroids

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13
Q

What is Pendred Syndrome?

A

Pendred Syndrome = mutation of pendrin gene (the transporter that transports iodide from follicular cells into follicular lumen in the thyroid)

Features:

  • goitre
  • sensorineural deafness
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14
Q

Which thyroid hormone is more potent?

A

T3 is more potent than T4

T4 converts itself to T3 via 5-deiodinase

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15
Q

What are the different types of 5-deiodinase and what do they do?

A

5-deiodinase Type 1 and Type 2 convert T4 to T3

Type 1: in thyroid, liver and kidneys
Type 2: in pituitary, brain, brown fat and thyroid

Type 3 inactivates T4 and T3, and makes reverse T3

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16
Q

What receptors do thyroid hormones act on?

A

Nuclear thyroid receptors TRalpha and TRbeta

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17
Q

What are the biochemical markers of thyrotoxicosis?

A

INCREASED:

  • osteocalcin
  • ALP
  • ANP
  • SHBG
  • Ferritin
  • vWF

DECREASED:

  • LDL
  • Lipoprotein (a)
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18
Q

What are the biochemical markers of hypothyroidism?

A

INCREASED:

  • CK
  • LDL
  • Prolactin
  • Lipoprotein (a)
  • Noradrenaline

DECREASED:
- vasopressin

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19
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

Osteocalcin

A

INCREASED in THYROTOXICOSIS

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20
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

CK

A

INCREASED in HYPOTHYROIDISM

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21
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

Noradrenaline

A

INCREASED in HYPOTHYROIDISM

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22
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

Vasopressin

A

DECREASED in HYPOTHYROIDISM

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23
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

ALP

A

INCREASED in THYROTOXICOSIS

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24
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

LDL

A

DECREASED in THYROTOXICOSIS

INCREASED in HYPOTHYROIDISM

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25
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

SHBG

A

INCREASED in THYROTOXICOSIS

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26
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

vWF

A

INCREASED in THYROTOXICOSIS

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27
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

Lipoprotein (a)

A

DECREASED in THYROTOXICOSIS

INCREASED in HYPOTHYROIDISM

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28
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

ANP

A

INCREASED in THYROTOXICOSIS

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29
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

Prolactin

A

INCREASED in HYPOTHYROIDISM

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30
Q

Is _____ a biochemical marker of thyrotoxicosis or hypothyroidism?

Ferritin

A

INCREASED in THYROTOXICOSIS

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31
Q

What are the two types of Primary Autoimmune Hypothyroidism?

A

Hashimotos

Atrophic Thyroiditis

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32
Q

What risk factors (non-genetic) are associated with Primary Autoimmune Hypothyroidism?

A

Female

Older age

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33
Q

What conditions are associated with Primary Autoimmune Hypothyroidism (ie Hashimotos or Atrophic Thyroiditis)

A
  • Pernicious anaemia
  • Type 1 Diabetes
  • Addisons
  • Vitiligo
  • Myasthenia Gravis
  • Pituitary autoimmunity
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34
Q

What genetic associations are with Primary Autoimmune Hypothyroidism?

A

HLA -DR3, -DR4, -DR5

CTLA-4

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35
Q

What is the pathogenesis of Primary Autoimmune Hypothyroidism?

A

Lymphocytic infiltration of thyroid with CD4+ and CD8+

  • germinal centre formation
  • atrophy of follicles
  • absence of colloid
  • mild-mod fibrosis
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36
Q

What diagnostic tests would you do for Primary Autoimmune Hypothyroidism?

A

Anti-TPO (90-95% spec and sensitivity)

Anti-TSH receptor antibody (20%)

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37
Q

How do you treat Primary Autoimmune Hypothyroidism?

A 
L thyroxine (aim for TSH ~1)
Start low if ischaemic heart disease

T3 not needed

PREGNANCY: increase dose by 50%

38
Q

What must you be cautious of when treating Primary Autoimmune Hypothyroidism? What can be unmasked?

A

In pituitary disease you can unmask the HPA axis with hypoadrenalism and diabetes mellitus

39
Q

What lab markers would you expect for subclinical hypothyroidism?

A

Raised TSH with NORMAL T4/T3

40% have anti-TPO

40
Q

What risk factors for subclinical hypothyroidism?

A

Older patients
Type 1 diabetes
Downs Syndrome

41
Q

What is the progression to hypothyroidism in subclinical hypothyroidism?

A

If the TSH >=1 then 100% progression

42
Q

When do you treat subclinical hypothyroidism?

A

Treat if symptoms or TSH >=10

If PREGNANCY: treat if TSH >=2.5

Consider if:

  • age <65yrs
  • heart failure
  • dyslipidaemia
  • anti-TPO or anti-Tg positive
43
Q

What are the clinical features of Myxoedema Coma?

A
  • dry coarse skin (yellow from carotene)
  • delayed reflexes
  • pericardial and pleural effusions
    +/- goitre
  • myopathy and cardiomyopathy
  • elevated CK
  • central hypothermia / bradycardia
  • seizures
44
Q

What precipitates myxoedema coma?

A

Trauma or major illness

45
Q

What lab findings do you expect in myxoedema coma?

A

TSH VERY high (>50!!!)
Hyponatraemia
Elevated creatinine
Elevated CO2

46
Q

How do you manage myxoedema coma?

A

HDU/ICU
Passive rewarming
Fluid resus +/- inotropes

IV hydrocortisone
T4 loading

VTE prophylaxis

REMEMBER reduced renal clearance

47
Q

What demographics are patients who present with Graves Disease?

A

Women predominant

Aged 20 - 50 years old

48
Q

What two organisms have been proposed to contribute to a molecular mimicry as part of pathogenesis of Graves Disease?

A
  • H pylori

- yersinia enterocolitis

49
Q

What immune modulating therapies have been associated with developing Graves Disease?

A
  • IFNalpha and IFNbeta
  • ipilumumab
  • HAART therapy
  • Alemtuzumab
  • lymphocyte depletion treatments
50
Q

What genetic associations are with Graves Disease?

A 
HLA-DR
CTLA-4
CD25
PTPN22
FCRL3
CD226
51
Q

What are the Graves-Specific features which present in addition to thyrotoxicosis features with Graves Disease?

A 
Goitre
Ophthalmopathy
Pretibial myxoedema
Thyroid acropachy
Myopathy
Onycholysis
Psychosis / aesthenia
Osteoporosis
AF with HIGH EMBOLISM RISK
Heart failure and IHD exacerbation
Neutropenia, lymphocytosis and thrombocytopenia
52
Q

What are the Graves-Specific musculoskeletal features of Graves Disease?

A

Myopathy

Osteoporosis

53
Q

What are the Graves-Specific cardiac features of Graves Disease?

A

AF with HIGH EMBOLISM RISK

Heart failure and IHD exacerbation

54
Q

What gender distribution is seen in Graves Ophthalmopathy?

A

Male > Female

55
Q

What are the eye features of Graves Ophthalmopathy?

A 
Exophthalmos
Proptosis and lid lag 
Periorbital lid swelling and chemosis
Diplopia and poor convergence
Limited upward gaze
Reduced visual acuity
56
Q

What causes the proptosis and lid lag seen in Graves Opthalmopathy?

What causes the reduced visual acuity seen in Graves Ophthalmopathy?

A

Proptosis and lid lag is due to overactivity of sympathetic stimulation in levator

Reduced visual acuity is due to retinal and optic nerve oedema

57
Q

What are the risk factors for progression of Graves Ophthalmopathy?

A

Smoking (STRONGEST)
Hypothyroidism
Iodine 131

58
Q

What is Hypokalaemic Periodic Paralysis

A

Transient hypokalaemia often post carbohydrates and exercise
Seen in Asian males

Acquired forms are seen in hyperthyroidism during THYROTOXIC phases

59
Q

What is the natural history of Graves Disease?

A

25% of untreated will spontaneously remit

If conservated treatmetn: 50% will remit

Once remission:
25% recur
25% become hypothyroid

60
Q

How do you manage the symptoms of Graves Disease?

A

Beta blockers

61
Q

How do you treat Graves Disease?

A

Symptom management with beta blockers

Antithyroid drugs: avoid permanent ablation
(propylthiouracil and carbimazole)
FAVOURED IF:
- age <40yrs with small goitre
- during pregnancy
- low titre TR-Abs
62
Q

Mechanism of Propylthiouracil?
Use in pregnancy?
Side effects?

A

Propylthiouracil (PTU)
- shorter half life than carbimazole

Action:
At Thyroid: inhibits thyroperoxidase to inhibit oxidation of iodide to iodine

At peripheries: inhibits 5-deiodinase to inhibit conversion of T4 to T3

PREGNANCY:

  • safer than carbimazole in 1st trimester
  • safe in breast milk at doses <300mg/day

S/E:

  • (rare) fulminant hepatitis
  • ANCA positive vasculitis
63
Q

Mechanism of Carbimazole?
Use in pregnancy?
Side effects?

A

Carbimazole (CBZ)
- 1st line in treatment due to risk for hepatitis with PTU

Action:
Carbimazole is a pro drug, later converted to methimazole which inhibits thyroperoxidase to inhibit oxidation of iodide to iodine

PREGNANCY:
- in 1st trimester causes foetal damage

S/E:

  • rash
  • mild neutropenia
  • agranulocytosis (0.4%)
64
Q

Use of Iodine 131 in treatment of Graves Disease?

A

Safe but causes hypothyroidism
Can EXACERBATE ophthalmopathy
Use in adults >40yrs who have failed other treatments

65
Q

Use of surgery in treatment of Graves Disease?

A

Most RAPIDLY effective
BEST for obstructive goitre

S/E:

  • hypothyroidsim
  • hypoparathyroidsim
  • laryngeal nerve damage
66
Q

TSHr mutation mediated hyperthyroidism presents similarly to, and is treated similarly as, Graves Disease.

What three risk factors for TSHr mutation mediated hyperthyroidsim?

A

Older
Women
Iron deficiency

67
Q

What are the two types of Amiodarone Induced Thyrotoxicosis (AIT) and how do you differentiate them?

A

AIT Type 1: Increased thyroid hormone due to iodine load
AID Type 2: thyrocyte toxicity

To differentiate:

  • Scan uptake is LOW in both
  • IL-6 is ELEVATED in Type 2
  • Tg is ELEVATED in Type 2
  • Vascularity: REDUCED in type 2, INCREASED/NORMAL in type 1
68
Q

What is, and when do you treat, subclinical hyperthyroidism?

A

Subclinical hyperthyroidism = subnormal TSH but normal T4 and T3

WHEN TO TREAT?

  • TSH <0.1
  • Multinodular goitre
  • Coexisting AF or osteoporosis
69
Q

How do you treat subclinical hyperthyroidism?

A

Thionamides for young patients with subclinical Graves
Radioiodine if older or multinodular goitre
Surgery if LARGE multinodular goitre

70
Q

What are the features of a thyroid storm?

A 
Fever (usually >40) and diaphoretic
Tachycardic and AF
CCF and APO
Proximal myopathy
Dehydration and shock
71
Q

What are precipitants of a thyroid storm?

A

Infection/trauma
Radioiodine
Noncompliance

72
Q

What is the management of thyroid storm?

A

HDU/ICU

Beta Blocker: IV propranolol to aim for HR 90bpm then oral 40-80mg TDS

PTU preferred to CBZ as it is more rapid

Lugol’s drops (BUT if used >=4 days then will worsen the thyrotoxicosis)

Cholestyramine will increase T4 clearance

Hydrocortisone will block thyroid output and T4–>T3 conversion

Plasmapheresis

73
Q

What medication must you AVOID in a thyroid storm?

A

Aspirin

Avoid it to prevent decreased protein binding and subsequent increases in free T3 and T4 levels

74
Q

What demographic tend to get thyroiditis?

A

Females

Aged 30 - 50yrs

75
Q

What is the implied pathogenic trigger for thyroiditis?

A

Viral infection

76
Q

What genetic association with thyroiditis?

A

HLAB35 in 75%

77
Q

What clinical features for thyroiditis?

A

PAINFUL goitre
Jaw pain and hoarse voice
Constitutional symptoms and fevers
Symptoms of thyrotoxicosis for 2-6 weeks

78
Q

What lab findings are expected with thyroiditis?

A

Elevated ESR and CRP

Elevated T3/T4 with REDUCED TSH
hypothyroid phase happens post thyrotoxic phase

79
Q

What treatment for thyroiditis?

What complications of thyroiditis?

A

Aspirin and NSAIDs
Prednisolone
Thyroxine if a prolonged hypothyroid phase

10% get permanent hypothyroidism

80
Q

What are the clinical features for Lymphocytic and Post Partum Thyroiditis?

A

PAINLESS goitre

NORMAL ESR

81
Q

What lab findings are expected for Lymphocytic and Post Partum Thyroiditis? What biopsy findings?

A

Anti-TPO Ab (ESPECIALLY IF POST PARTUM!)
Low-zero uptake on US
Biopsy: lymphocytic infiltration

82
Q

What is the clinical course of Lymphocytic and Post Partum Thyroiditis?

A

Hyperthyroid for 2-4 weeks

Hypothyroid from 4-12 weeks

83
Q

How do you treat Lymphocytic and Post Partum Thyroiditis?

A

Symptoms management with beta blocker

Treat with thyroxine if prolonged hypothyroidism

84
Q

Presentation and treatment of Riedel’s Thyroiditis?

A

RARE
Occurs in middle aged women
? part of IgG4 Systemic Disease

Usually presents with fixed painless thyroid mass

Treat with surgery, steroids and TAMOXIFEN

85
Q

What associated features are with Riedel’s Thyroiditis?

A

Horners
Carotid stenosis
Hypoparathyroidism

86
Q

THROID & DRUGS:

Lithium?

A

Lithium can cause both hypothyroidims and thyroiditis

87
Q

THROID & DRUGS:

Immune checkpoint inhibitor antibodies?

A

Ipilumumab & Tremilimumab (anti-CTLA4)

  • central hypothyroidism (5%)
  • thyroiditis (2%)

Nivolumumab & Pembrolizumab (anti-PD1)

  • thyroiditis (4%)
  • central hypothyroidism (<1%)
88
Q

THROID & DRUGS:

Alemtuzumab?

A

Alemtuzumab (anti-CD52)

  • Graves (15%)
  • Thyroiditis
89
Q

THROID & DRUGS:

Interferon-Alpha?

A

Interferon alpha

  • anti-TPO and anti-Tg (15%)
  • Hypothyroidism (5%)
  • Graves
90
Q

THROID & DRUGS:

Tyrosine kinase inhibitors?

A

Hypothyroidism (25%)

91
Q

THROID & DRUGS:

Bexarotene?

A

Bexarotene (RXR agonist)
- central hypothyroidism (impairs TSH release)
and increases T4 clearance

RACP Written 2018 (167 decks)

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