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3152 - nat > thyroid drugs ic11 + ic15 > Flashcards

thyroid drugs ic11 + ic15 Flashcards

1
Q

Causes of Hyperthyroidism (3 points)

A

1) Grave’s disease
TSH receptor antibodies (TRAb) mimicking TSH binding, stimulate TH production

2) Subacute thyroiditis
Release of stored thyroid hormone
Cause Hyper, then Hypo

3) Adenomas, nodules

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2
Q

Treatment for Hyperthyroidism (3 points, surgery, list drugs)

A

1) Surgical resection, Thyroidectomy

2) Radioactive iodine ablative therapy
Destroy overactive thyroid cells
CANNOT give in pregnancy

3) Antithyroid drugs
Thionamides (Carbimazole and Propylthiouracil)
Iodides
Non-selective beta blockers

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3
Q

Patients suitable for antithyroid drugs

A

1) Waiting for ablative therapy or surgical resection (except KI, do ablation first then KI)
Minimise risk of post-ablation hyperthyroidism
Depletes stored hormone

2) Mild disease, small goiter

3) Women, elderly

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4
Q

Examples of drugs that can block TPO

A

Class: Thionamides

Propylthiouracil
Carbimazole

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5
Q

What do patients with hepatotoxicity take?

A

Carbimazole

DO NOT take PTU

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6
Q

Why can Carbimazole be taken OD?

A

Concentrated in thyroid → Effect lasts whole day

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7
Q

Counselling point for Carbimazole / PTU

A

Clinical response may take 3-6 weeks
Existing T4 still persists in body, has long half life
Need to wait for present molecules to be degraded

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8
Q

Example of NSBB used in Hyperthyroidism

Why can NSBB be used in Hyperthyroidism?

A

Propranolol

Used for symptomatic relief!
Reduces adrenergic symptoms
Blocks T4 to T3 conversion at high dose

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9
Q

What can Propranolol be used together with?

Why?

A

Thionamides eg. PTU, Carbimazole

Propranolol used for short term symptomatic relief of hyperthyroidism symptoms

Thionamides take very long (3-6 weeks) to reduce T3 T4 levels, so Propranolol is taken in the meantime

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10
Q

Which drugs can block T4 to T3 peripheral conversion?

A

PTU and Propranolol

can block at high doses

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11
Q

Indication of NSBB (3 points)

A

Short term symptomatic relief
Used with Thionamide, before ablation, surgery
Treatment for thyroiditis

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12
Q

MOA of Iodides

example of iodide

A

Inhibit release of stored T3T4
Has minimal effect on TH synthesis
Limited efficacy after 14 days

Potassium iodide

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13
Q

Indication of iodides

A

Before surgery to shrink gland

After ablative therapy, inhibit thyroiditis-mediated release of stored TH

Thyroid storm

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14
Q

Can use KI before ablative radioactive iodine therapy?

A

No, do not use before ablative radioactive iodine therapy

Radioactive Iodine first -> then Potassium Iodide

May reduce uptake of radioactive iodine

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15
Q

Which drugs to use during hyperthyroidism in pregnancy?

A

1st trimester: Use PTU
Carbimazole has higher risk of congenital malformations

2nd, 3rd trimester: Use Carbimazole
PTU has higher risk of hepatotoxicity

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16
Q

Causes of Hypothyroidism

A

Primary
1) Iodine deficiency
2) Hashimoto disease
Increased AtgA and TPO antibodies which attack thyroid
3) Thyroid resection

Secondary
1) Hypothalamus (TRH) or Pituitary dysfunction (TSH)
2) Drug induced eg. amiodarone, lithium

17
Q

Lab signs of Primary and Secondary Hypothyroidism (eg. TSH, T4, antibody levels)

A

Primary hypo
High TSH, Low T4
Positive antibodies (TPO, ATgA)

Secondary hypo
Low TSH, low T4

18
Q

What is levothyroxine?

A

Synthetic T4

19
Q

Dose of Levothyroxine (Healthy adults, 50-60yo without or with CVD)

A

Divide by 2 each time

Young, healthy adults: 100mcg
50-60yo with no cardiac issues: 50mcg
With CVD: 12.5 - 25 mcg

20
Q

When should Levothyroxine be taken?

A

Take on empty stomach
30 - 60 mins before breakfast
4 hours after dinner

Take 2 hours from calcium or iron supplements

21
Q

What is the target TSH level to reach during Levothyroxine therapy?

A

0.4 - 4

Titrate Levothyroxine dose based on symptoms, TSH level

22
Q

What is Myxoedema coma?

A

Severe progression of Hypothyroidism
Reduced blood flow to GI, affect gut absorption of oral levothyroxine

Use IV Liothyronine (T3) or Levothyroxine

23
Q

What is Liothyronine?

A

Synthetic T3

Has faster onset than Levothyroxine

24
Q

Why does Hypothyroidism happen in Pregnancy?

What should be done to Levothyroxine dose?

A

Increased TBG which binds to T3 and T4

Need to increase Levothyroxine dose by 30-50% in pregnancy

25
Q

What is the target TSH levels during pregnancy? (during each trimester)

A

Should be low

1st trimester < 2.5
2nd trimester < 3
3rd trimester < 3.5

26
Q

When should subclinical Hypothyroidism be treated? (at what TSH level)

A

TSH > 10mIU/L
OR
TSH between 4 - 10
+ symptoms of hypothyroidism, TPO antibodies present
History of CVD, HF

27
Q

What is the Negative feedback loop in Thyroid production?

A
  1. Hypothalamus detect low circulating TH, releasing Thyrotropin Releasing Hormone (TRH)
  2. TRH instructs anterior pituitary to release Thyroid Stimulating Hormone (TSH)
  3. TSH travels to Thyroid gland, gland produces Thyroid hormones (TH)
  4. Hypothalamus sense increased TH and stops releasing TRH
28
Q

TSH levels in primary hypo VS hyper

A

High TSH in primary hypo
Issue: Thyroid gland not working, does not produce T3, T4
Low T3 and T4 will cause Hypothalamus to increase TRH, which increases TSH by anterior pituitary

Low TSH in primary hyper
Issue: Thyroid gland producing too much T3, T4
Hypothalamus sense high TH, decrease TRH secretion which decreases TSH production in anterior pituitary

29
Q

Between T3 and T4,

Which is produced more?
Which is more potent
Which has longer half life?

A

T4 produced 4 times more than T3

T3 more potent

T4 has half-life of 6-7 days
T3 has half life of 2 days

30
Q

What is TBG?

When is TBG elevated?

A

TBG = Thyroxine Binding Globulin

Elevated in pregnancy or females on estrogen contraceptive

31
Q

Who requires routine screening for thyroid antibodies?

A

Pediatric patients, pregnant women

32
Q

What monitoring should be done during Hyper and Hypothyroidism treatment?

A

Hyper:
Use T3, better than T4 early in therapy + TSH will be suppressed during treatment

Hypo:
Use TSH
(unless central hypo, then TSH will be low) use T4

3152 - nat (16 decks)

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