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Stage 3 Case 4 > Hyper/hypothyroidism > Flashcards

Hyper/hypothyroidism Flashcards

1
Q

What is the thyroid gland made up of (anterior)?

A

Pyramidal lobe (sometimes absent)
Right lobe
Isthmus
Left lobe

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2
Q

What is the thyroid gland made up of (posterior)?

A

Superior parathyroid glands

Inferior parathyroid glands

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3
Q

What is main function of the thyroid gland?

A

Synthesis thyroid hormones (T3 and T4), thyroxine.

Secretion of calcitonin

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4
Q

Where is the thyroid gland found?

A

At the base of the neck

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5
Q

What is the functions of parathyroid?

A

Maintenance of serum calcium and phosphate levels through secretin of parathyroid hormone (PTH)

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6
Q

What effects to T3 and T4 have one the body? (4)

A

1) Cardiovascular
2) Metabolic
3) Developmental
4) Other

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7
Q

What produces T3 and T4?

A

Iodine (Mono and Di)

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8
Q

Thyroid hormones mechanism?

A
  1. Hypothalamus = TRH
  2. Pituitary = TSH
  3. Thyroid = T4 and T3 to go and work peripherally (T2 excreted)
  4. Then feedback to pituitary and hypothalamus to turn off.
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9
Q

What is ratio of T4 and T3 produced?

A

10:1 (more T4)

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10
Q

Types of hypothyroidism

A

Primary
Secondary
Peripheral

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11
Q

What is primary hypothyroidism?

A

Disfunction in the thyroid itself.

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12
Q

What is secondary hypothyroidism?

A

Reduced thyroid stimulation (TSH or TRH)

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13
Q

What is peripheral hypothyroidism?

A

Circulating levels are enough but the body cannot use them

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14
Q

Causes of hypothyroidism (5)

A
  • Autoimmune thyroiditis
  • Iodine deficiency
  • Post thyroidectomy or radioactive iodine treatment
  • Drug induced (lithium)
  • Peripheral resistance to thyroid hormone
  • Congenital diseases e.g., thyroid agenesis
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15
Q

Diagnosis of hypothyroidism

A
  1. Sympotoms

2. Biochemical testing – Thyroid function and TSH and Free T4

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16
Q

Why does a high TSH indicate hypothyroidism?

A

Because they body if not producing enough thyroxine, so the body is indicating the need for more via TSH

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17
Q

High TSH and normal T4 =

A

Subclinical hypothyroidism (just about able to manage)

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18
Q

Low TSH and normal T4

A

Subclinical hyperthyroidism (just about able to manage)

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19
Q

High TSH and low T4 =

A

Primary hypothyroidism (likely autoimmune thyroiditis)

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20
Q

Low TSH and high T4 =

A

Primary hyperthyroidism (likely Graves’ disease)

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21
Q

Aim for treatment for hypothyroidism

A
  1. Effectivly replace thyroid hormone

2. Correct TSH levels and resolve clinical symptoms

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22
Q

1st line drug for hypothyroidism

A

Levothyroxine (T4 replacement)

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23
Q

What do you do with people with glucocorticoid deficiency before starting thyroxine?

A

Glucocorticoid replacement

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24
Q

What is monitored in use of thyroxine?

A

TFTs every 3 months until stable then annually

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25
Q

How long can it take for TSH to stabiles with use of thyroxine?

A

6 months. Most adults stabiles at does between 100-200 micrograms. (do not really go over)

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26
Q

In what doses is thyroxine titrated?

A

25 micrograms

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27
Q

How is thyroxine dose decided?

A

Based on weight (1.6/kg rounded to nearest 25 microgram)

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28
Q

Why are drug interaction important for thyroxine?

A

It get absorbed and bounds reduces its use.

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29
Q

Thyroxine main interactions

A

Calcium and iron should not be taken at the same time as they bind. Also PPIs.
Milk

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30
Q

How may IBD or coeliac impact levothyroxine dose?

A

May need higher doses due to absorption issues.

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31
Q

How to take levothyroxine?

A

In the morning 30-60 mins before food.

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32
Q

Side effects of levothyroxine

A 
Flushing
 Restlessness
 Palpitations
 Insomnia
 Angina
 Thyroid crisis
33
Q

Liothyronine

A

Synthetic form of T3
IV and rarely used not non-oral usage
Usually switch everyone to levothyroxine

34
Q

What happens to levothyroxine dose when pregnant?

A

Increase by 20-25 micrograms immediately and have TSH levels checked. Monitoring every 4-6 weeks.
Go back to normal dose after birth
Can use while breastfeeding

35
Q

TSH target levels pregnancy

A

First trimester <2.5 mU/L

Third trimester <3.0 mU/L

36
Q

Myxedema crisis

A

Extreme manifestation of hypothyroidism.

Rare but potentially fatal

37
Q

Graves’ disease (hyperthyroid) symptoms

A

Bulding eyes
Eyelids retracts
Redness

38
Q

Nodular disease (hyperthyroid)

A

Can be single or multiple goiter
Actively release T3/T4
Images using radioactive iodine

39
Q

Thyroiditis (hyperthyroid)

A

Inflammation of the thyroid follicles (usually painful and tender)
Causes by infection, trauma, drug induced or autoimmune medicated.
T3 and T4 leaked from inflamed cells
-Can go or cause lots of damage

40
Q

Diagnosis for hyperthyroidism

A

Thyroid function tests TSH , Free T4 and T3 and TRABs

41
Q

Low TSH but high FT4 and FT3 =

A

Hyperthyroidism of thyroidal region

42
Q

High TSH and high FT4 and FT3 (RARE) =

A

Hyperthyroidism of external origin indicating pituitary or hypothalamic disease .

43
Q

What is required for definitive diagnosis of hyperthyroidism?

A

2 sets of TFTs taken at least 6 weeks apart. Thyrotoxicosis usually used until further investigation.

44
Q

Hyperthyroidism treatment aim

A

Acute: manage symptoms

Chronic: Effectively suppress thyroid hormone back do euthyroid levels.

45
Q

Treatment options (3)

A

Antithyroid drugs
Radioactive iodine
Thyroidectomy

46
Q

Graves disease If patients are likely to go into remission: treatment

A

First line: Thionamides; carbimazole unless contraindicated.

47
Q

Graves disease If unlikely to go into remission: treatment

A

First line: Radioactive iodine

48
Q

Graves disease If concerns regarding possible compression or malignancy: treatment

A

First line: Thyroidectomy

49
Q

Multinodular goitre treatment

A

First line: Radioactive iodine

Second line: Either thionamides or thyroidectomy

50
Q

Single nodular adenoma treatment

A

First line: Either radioactive iodine or surgical intervention of total- or hemi-thyroidectomy
Second line: Thionamides

51
Q

Hyperthyroidism treatment pregnancy

A

1) Thionamides; propylthiouracil
2) Thyroidectomy
Radioactive iodine is contraindicated in both pregnancy and breastfeeding, as rarely can potentiate thyroid hormone release and even precipitate thyroid crisis which could be teratogenic.

52
Q

Graves’ Disease Children treatment

A

First line: Thionamides; carbimazole unless contraindicated.
If remission not achieved review for possible radioactive iodine or consider long-term therapy.

53
Q

MNG or SNA Children treatment

A

Initially commenced thionamides. Long-term will need to discuss risks and benefits of radioactive iodine or thyroidectomy

54
Q

Thionamides (Anti-thyroid Drugs) e.g.

A

Carbimazole and Propylthiouracil

55
Q

Thionamides (Anti-thyroid Drugs) uses

A

6-8 weeks to show benefit
Can titrate up
Or block and replace (loss in thyroid as it has been blocked)

56
Q

Carbimazole MOA

A

Mechanism of action: Inhibition of the organification of iodide and thyroglobulin and the coupling of iodothyronine residues which in turn
suppress the synthesis of thyroid hormones.

57
Q

What is Carbimazole

A

Pro-drug which undergoes metabolism by hepatic enzymes to the active metabolite, thiamazole, also known as methimazole.

58
Q

Carbimazole uses

A

First line choice due to quick thyroid hormone correction (4-8 weeks)
20-60mg in divided doses

59
Q

Carbimazole monitoring

A

TFTs checked every 6-8 weeks

Once thyroid levels are within range, can either block and replace or titrate for 12-18 months.

60
Q

Titration of Carbimazole (Thionamides Anti-thyroid Drugs)

A

5-15mg once daily. Regular TFT checks at hospital and dose adjusted to response

61
Q

Block and replace of Carbimazole (Thionamides Anti-thyroid Drugs)

A

remains on high starting dose to ensure endogenous T3/T4 production completely suppressed but levothyroxine is started alongside to supplement. Thyroxine is then titrated until TSH, T3 and T4 are within reference range.

62
Q

Carbimazole Contraindications

A
  • Severe hepatic impairment (unable to be metabolised to active methimazole)
  • Pre-existing blood disorders (risk of dyscrasias)
  • History of pancreatitis (may exacerbate)
63
Q

Carbimazole Side effects

A
  • Macropapular rash – can be treated with a generic antihistamine
  • Bone marrow suppression and some fatal cases of agranulocytosis have occurred in patients treated with carbimazole
  • On initiation patients need to be counselled on the signs and symptoms of blood dyscrasias – sore throat, bruising, bleeding, mouth ulcers, fevers and malaise
  • Full blood count to be checked as a baseline and 6 monthly during treatment
64
Q

Carbimazole Counselling

A
  • Advise on dose to be taken during initial dosing then dependent on regimen elected for and monitoring as appropriate to that regimen
  • Need for additional medications i.e. beta blockers for symptom management
  • May take six to eight weeks to have an observable effect as do not alter existing levels of T3 and T4.
  • Advised on the urgency of reporting onset of severe sore throats, bruising or bleeding, mouth ulcers, fever and malaise
  • Women of childbearing age advised for need for contraception due to teratogenic effects of carbimazole and previous cases of foetal malformation
65
Q

Carbimazole is a vitamin K antagonist

A

S o may intensify or potentiate effects of warfarin. Advise for closer INR monitoring when initiated and on dose changes if relevant to patient case

66
Q

Propylthiouracil MOA

A

Propylthiouracil achieves these actions by the inhibition of the enzyme peroxidase.
-Its effects are only begin to manifest after a latent period of up to 3 or 4 weeks because
all the preformed hormone has to be used up before circulatory concentrations will fall.
-Inhibits organification of iodide and the coupling of iodothyronine residues suppressing thyroid hormone production
-Inhibits conversion of T4 to T3 in peripheral tissues supressing thyroid hormone action

67
Q

Propylthiouracil uses

A

Most commonly second line for patients who have contraindications to or suffer
adverse reactions with carbimazole and in pregnancy

68
Q

Propylthiouracil monitoring

A

TFTs to be checked every 6-8 weeks
Once thyroid hormone levels are within reference range patients choose either ‘titration’
or ‘block and replace’ and continue for 12-18 months

69
Q

Titration of Propylthiouracil (Thionamides Anti-thyroid Drugs)

A

50-150mg once daily. Regular TFT checks at hospital and dose adjusted to
response

70
Q

Block and replace of Propylthiouracil (Thionamides Anti-thyroid Drugs)

A

remains on high starting dose to ensure endogenous T3/T4 production completely suppressed but levothyroxine is started alongside to supplement. Thyroxine is then titrated until TSH, T3 and T4 are within reference range.

71
Q

Propylthiouracil Contraindications

A
  • Severe hepatic impairment (unable to be metabolised to active methimazole)
  • Pre-existing blood disorders (risk of dyscrasias)
  • History of pancreatitis (may exacerbate)
72
Q

Propylthiouracil Side effects

A

-Macropapular rash – can be treated with a generic antihistamine
-Severe hepatic reaction causing acute liver injury; some cases of which were fatal and
some requiring liver transplant
-Bone marrow suppression, thrombocytopenia and risk of agranulocytosis
-On initiation patients need to be counselled on the signs and symptoms of blood
dyscrasias – sore throat, bruising, bleeding, mouth ulcers, fevers and malaise
-Full blood count to be checked as a baseline and 6 monthly during treatment

73
Q

Propylthiouracil Counselling

A

Advise on dose to be taken during initial dosing then dependent on regimen elected
for and monitoring as appropriate to that regimen
-Need for additional medications i.e. beta blockers for symptom management
-May take six to eight weeks to have an observable effect as do not alter existing
levels of T3 and T4.
-Advised on the urgency of reporting onset of severe sore throats, bruising or
bleeding, mouth ulcers, fever and malaise
-Some cases of severe hepatic reactions, both in adults and children, including fatal
cases and cases requiring a liver transplant have been reported with
propylthiouracil. Patients should be advised to report any jaundice, dark urine,
abdomen pain, pruritis, nausea and vomiting,
-Time to onset has varied but in most cases the liver reaction occurred within 6 months
-If significant hepatic enzyme abnormalities develop STOP treatment

74
Q

When switching from Carbimazole to Propylthiouracil

A
  • 1mg of carbimazole is roughly equivalent to 10mg of

propylthiouracil

75
Q

Post thyroidectomy

A
  • Start levothyroxine at standard 1.6microgram/kg dose immediately post-op total thyroidectomy
  • Post hemithyroidectomy monitor TSH at 2- and 6-months post surgery and start levothyroxine when/if indicated
76
Q

Thyroid Crisis aka Thyrotoxic Storm Treatment mechanism (4)

A
  • Inhibition of thyroid hormone synthesis
  • Inhibition of thyroid hormone release
  • Inhibition of peripheral action of excess thyroid hormone
  • Supplementary management
77
Q

Thyroid Crisis aka Thyrotoxic Storm Inhibition of hormone synthesis Treatment drugs (2)

A

-Carbimazole: 20-30mg every 4 to 6 hours
-Propylthiouracil: 600mg loading followed by 200-250mg every 4 to 6 hours
Oral, NG or rectal
Lots and quick

78
Q

Thyroid Crisis aka Thyrotoxic Storm Inhibition of peripheral hormone action Treatment drugs

A

Propranolol
If pre-existing asthma or COPD consider more Cardioselective beta blocker
e.g. metoprolol
If beta blockers contraindicated completely – rate limiting calcium channel blocker
Diltiazem
Glucorticosteroids inhibit peripheral T4 to T3 conversion.

79
Q

Thyroid Crisis aka Thyrotoxic Storm Additional symptom control and supplementary management Treatment drugs

A

Paracetamol for high temperature
Cholestyramine
-Enhances thyroid hormone excretion by increasing enterohepatic circulation
which is increased in thyroid storm
-Cholestyramine bile sequestrant binds free thyroid hormone to facilitate excretion
through faeces

Stage 3 Case 4 (11 decks)

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