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PHARM 343 > Thyroid > Flashcards

Thyroid Flashcards

1
Q

Primary Thyroid Disease

A

Affects Thyroid Gland (T4 and T3 secretion)

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2
Q

Secondary Thyroid Disease

A

Affects Pituitary Gland (TSH Secretion)

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3
Q

Tertiary Thyroid Disease

A

Affects Hypothalamus (TRH Secretion)

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4
Q

T4 vs T3
- Which is the main hormone secreted
- Which one is biologically active
- Which one is more protein bound
- Which one has the longer half life
- Which one is more potent

A

T4 (Thyroxine)
- Main hormone secreted
- Biologically Inactive
- 99.96% protein bound
- Half Life = 7 days (Longer half life due to being more protein bound than T3)

T3 (Triiodothyronine)
- 80% converted in periphery from T4
- Biologically Active
- 99.5% protein bound
- Half Life = 1-2 days
- 3x more potent at inhibiting TSH

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5
Q

Hyperthyroidism
- How much thyroid hormone
- Effect on metabolism

A

Too much thyroid hormone
Metabolism speeds up

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6
Q

Hypothyroidism
- How much thyroid hormone
- Effect on metabolism

A

Too little thyroid hormone
Metabolism slows down

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7
Q

TSH
- Value in Hyperthyroidism vs Hypothyroidism

A

TSH is low in Hyperthyroidism
TSH is high in Hypothyroidism

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8
Q

TSH
- Fluctuations in value

A

Will be at its highest around midnight
Will be at its lowest in late afternoon

Values are different in pregnancy and old age

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9
Q

When to use TSH

A

When screening for thyroid dysfunction
When screening for thyroid hormone replacement

Not good for pituitary diseases
- Use free T4 instead

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10
Q

When to use Free T4

A

TSH is low (Sign of hyperthyroidism)
- Use free T4 to evaluate thyrometabolic status

Use to confirm hyper/hypothyroidism
- Used as second test after TSH

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11
Q

When to use Free T3

A

Generally not used for hypothyroidism
- As T3 is usually low in absence of thyroid disease

Used to differentiate between different kinds of hyperthyroidism
- Ordered when TSH is low but T4 is normal/low

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12
Q

Who should be screened for Thyroid Disorders

A

Do not screen asymptomatic non-pregnant patients

Screen:
- Symptomatic patients
- Patients at increased risk

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13
Q

Patients at increased risk of thyroid disorders

A

Women older than 45

Postpartum Women

Patients taking lithium or amiodarone

Patients with auto immune disease
- Type 1 Diabetes
- Strong Family History

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14
Q

Tests for screening Primary Thyroid Disorders

A

TSH first

Do not use free T3 or free T4 for screening hypothyroidism or to adjust doses for patient with diagnosed primary hypothyroidism
- T3 and T4 are mostly protein bound so the amount in blood will normally be low

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15
Q

Hypothyroidism
- 2 Kinds

A

Subclinical:
- TSH high
- T4 normal

Overt:
- TSH high
- Free T4 is low

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16
Q

Hypothyroidism
- Signs and Symptoms

A

Similar to Hyperthyroidism:
- Hoarseness of Deepening of Voice
- Swelling (Goiter)
- Persistient Dry/Sore throat
- Difficulty Swallowing
- Infertility

Different from Hyperthyroidism
- Puffy Eyes
- Cold Intolerance
- Weight Gain
- Elevated Cholesterol
- Tiredness
- Forgetful/Slower thinking
- Depression
- Muscle weakness/cramps
- Slower heartbeat
- Constipation

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17
Q

Hypothyroidism
- High risk populations

A
  • Women (postpartum) - 3x more risk
  • Prior history of graves diseease
  • Increasing age (especially after 60)
  • Family history of autoimmune thyroid disease
  • Other autoimmune endocrine conditions (Type 1 diabetes)
  • Other autoimmune non-endocrine conditions (Celiac disease, Pernicious anemia)
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18
Q

Hypothyroidism
- Primary

A

Primary (99%)
- Hasimoto’s Disease
- Iatrogenic Hypothyroidism
- Iodine Excess/Deficiency
- Drugs
- Congenital

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19
Q

Hypothyroidism
- Secondary/Tertiary

A

Secondary/Tertiary (1%)
- Pituitary Disease
- Hypothalamic Disease

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20
Q

Hashimoto’s Disease

A

Primary Hypothyroidism
- Elevated Thyroid Peroxidase Antibody, attacks and impairs Thyroid Peroxidase
—> Lowers amount of thyroid hormone

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21
Q

Iatrogenic Hypothyroidism

A

Radiated Iodine
- Destroys thyroid gland
Thyroidectomy

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22
Q

What drugs cause hypothyroidism

A

Lithium
Amiodarone
Antithyroid drugs

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23
Q

Effect of Excess Iodine on Thyroid

A

Causes a surge in thyroid hormone
- Then causes white blood cells to infiltrate thyroid and impairs it from producing thyroid hormone

Causes Hypothyroidism

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24
Q

Effect of Deficiency Iodine on Thyroid

A

Hypothyroidism

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25
Q

Hypothyroidism Treatment
- Pharmacological

A

Levothyroxine

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26
Q

Hypothyroidism Treatment
- Pharmacological Dose

A

Long half life, once a day dosing

Dose depends on:
- Age
- Body weight
- Pregnancy status
- Cardiac Disease

Severity of hypothyroidism
- If subclinical = Lower dose
- If RAI or Thyroidectomy = Higher dose

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27
Q

Hypothyroidism Treatment
- Pharmacological Absorption

A

Take 30-60 minutes before breakfast with water

Should be take on empty stomach
- Separate by 4 hours with Iron, Calcium, Multivitamins

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28
Q

Levothyroxine Dose
- Healthy Adult

A

1.6 mcg/kg

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29
Q

Levothyroxine Dose
- Elderly (65 years or above)

A

1.0 mcg/kg
- Average maintenance dose is 100mcg
- Initiation should be at lower dose and titrated slowly (Start at 12.5-25mcg)

As patient ages dose should decrease

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30
Q

Levothyroxine Dose
- Cardiac Patients (Or at risk)

A

12.5-25mcg
- Initiate at low dose and titrate slowly
- Avoid cardiac compromise and ischemia (Avoid increasing BP and HR)

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31
Q

Levothyroxine
- Monitoring

A

Primary Hypothyroidism: Monitor TSH levels
Secondary Hypothyroidism: Monitor Free T4 levels

Monitor every 6-8 weeks after initiation/dose change until euthyroid
- Adjust as needed until values are euthyroid
- Once euthyroid monitor yearly, or until new symptoms appear

32
Q

Over treatment of Levothyroxine

A
  • Atrial fibrillation and Stroke
  • Increased risk of Angina and Myocardial Infarction in Cardiac Patients
  • Bone Loss and Fractures
  • Anxiety, Sleep Disturbance, Irritability
33
Q

Under treatment of Levothyroxine

A
  • Increased lipids
  • Decreased heart rate and ventricular contractility
  • Increased peripheral vascular resistance and diastolic pressure
  • Memory loss
  • Mood impairment
34
Q

Levothyroxine in Healthy Patients
- Low Dose vs Full Dose (1.6 mcg/kg)

A

Full dose is more convenient and cost effective, achieves Euthyroidism faster

35
Q

Hypothyroidism Treatment
- Desiccated Thyroid

A

Lower T4:T3 ratio is lower than what is secreted by human thyroid gland
- Supraphysiologic levels of T3
- Animal derivative

Not recommended

36
Q

Hypothyroidism Treatment
- Liothyronine

A

Basically synthetic T3
- Short half life, has to be dosed twice a day
- Increases Cardiac Adverse Drug Reaction

37
Q

Hypothyroidism Treatment
- Combination

A

Levothyroxine + Liothyronine
- No evidence of benefit
- Small subset of patients do better (Those that remain symptomatic on levothyroxine)

Summary: Consider if patient remains symptomatic on levothyroxine
- Have to carefully monitor

38
Q

Factors that reduce Levothyroxine Effectiveness

A

Malabsorption Symptoms

Reduced Absorption

Drugs that increase clearance

Factors that decrease T4 conversion to T3

39
Q

Factors that reduce Levothyroxine Effectiveness
- Malabsorption Symptoms

A

Short Bowel
Celiac Disease

40
Q

Factors that reduce Levothyroxine Effectiveness
- Reduced Absorption

A

Sucralfate
Food
Ferrous Salts
Calcium Supplements
Aluminum Hydroxide
Cholestyramine

41
Q

Factors that reduce Levothyroxine Effectiveness
- Drugs that increase clearance

A

Rifampin
Carbamazepine
Phenytoin

42
Q

Factors that reduce Levothyroxine Effectiveness
- Decreases T4 conversion to T3

A

Amiodarone

43
Q

Hypothyroidism
- Pregnancy

A

Thyroid function changes in pregnancy
- May have to increase dose

Untreated hypothyroidism can affect cognitive function of child and increase maternal hypertension, preeclampsia, postpartum hemorrhage, spontaneous abortion, fetal death

44
Q

Hyperthyroidism
- Symptoms

A

Similar to Hypothyroidism
– Hoarseness of Deepening of Voice
- Swelling (Goiter)
- Persistient Dry/Sore throat
- Difficulty Swallowing
- Infertility

Different from Hypothyroidism
- Budging eyes
- Heat Intolerance
- Weight Gain
- Rapid/Irregular Heartbeat
- Nervousness
- Irritability
- Frequent bowel movements
- Increased sweating
- First trimester miscarriage

45
Q

Hyperthyroidism
- Etiology

A
  • Graves’ Disease
  • Toxic Nodules
  • Tumours
  • Subacute Thyroiditis
  • Hashitoxicosis
  • Excessive Dosage of T3 or T4
46
Q

Graves’ Disease

A

Hyperthyroidism (Seen in younger female patients)
- Body produces antibodies that activate the thyroid gland

47
Q

Toxic Nodules

A

Hyperthyroidism (Seen in elderly)
- Creates lots of T3 and T4
- Does not respond to negative feedback

48
Q

Tumours

A

Hyperthyroidism
- Excessive stimulation of thyroid gland

49
Q

Subacute Thyroiditis

A

Hyperthyroidism in first phase
- Then white blood cells infiltrate and damage the thyroid gland leading to hypothyroidism

50
Q

Hashitoxxicosis

A

Hyperthyroidism in first phase
- Then white blood cells infiltrate and damage the thyroid gland leading to hypothyroidism

51
Q

Excessive Dosage with T3 or T4

A

Hyperthyroidism

52
Q

Autoimmune Endocrine Disorders associated with Graves’ Disease

A
  • Addison’s Disease
  • Type 1 Diabetes
  • Primary Gonadal Failure
  • Hashimoto’s Thyroiditis
53
Q

Autoimmune Non-Endocrine Disorders associated with Graves’ Disease

A
  • Celiac Disease
  • Myasthenia Gravis
  • Pernicious Anemia
  • Immune Thrombocytopenic purpura
  • Rheumatoid Arthritis
54
Q

Hyperthyroidism
- Treatment

A

Drugs
Radioactive Iodine
Surgery

55
Q

Hyperthyroidism
- Beta Blockers initiation

A

Used to control symptoms, should not be sole therapy
- Can be initiated at presentation before diagnosis

56
Q

Hyperthyroidism
- Beta blockers For who

A

Considered for patients with:
- Symptomatic Thyrotoxicosis
- Elderly
- Resting heart rate greater than 90
- Coexistent CV disease

57
Q

Hyperthyroidism
- Beta blockers which to choose

A

All are equally effective
- Some may impair T3 to T4 conversion but has not shown to be clinically significant

58
Q

Hyperthyroidism
- Antithyroid Drugs

A

Propylthiouracil (PTU)
Methimazole

59
Q

Hyperthyroidism
- Antithyroid Drugs Mechanism

A

Inhibits Thyroid Peroxidase and synthesis of thyroid hormone
–> Less thyroid hormone

PTU blocks peripheral T4 to T3 conversion

60
Q

Hyperthyroidism
- Antithyroid Drugs Response

A

Higher likelihood of response:
- Older patients (Greater than 40 years old)
- Small goiters
- Short duration of disease
- Small amounts of Thyroid Peroxidase Antibody

61
Q

Hyperthyroidism
- Antithyroid Drugs Long Term Treatment

A

Best to use Methimazole

62
Q

Hyperthyroidism
- Antithyroid Drugs First Line

A

Methimazole is preferred as first line
- Except 1st trimester of pregnancy where PTU is preferred

63
Q

PTU vs Methimazole
- Half Life

A

Methimazole has a higher half life
- Can be dosed less frequently at lower doses

64
Q

PTU vs Methimazole
- Side Effects

A

PTU has higher risks of side effects

65
Q

PTU vs Methimazole
- Pregnancy

A

Methimazole is not to be used in first trimester of pregnancy
- Use PTU instead

66
Q

Hyperthyroidism
- Antithyroid Drugs Side Effects

A
  • Skin Rash
  • Allergic Reaction
  • Agranulocytosis
  • Hepatotoxicity (Greater chance in PTU)
67
Q

Hyperthyroidism
- Antithyroid Drugs Counseling

A

Stop medication if experiencing rash, fever, jaundice, sore throat

68
Q

Hyperthyroidism
- Antithyroid Drugs Lab Tests

A
  • Baseline CBC (Include WBC and differential)
  • ALT/AST
  • Bilirubin
69
Q

Hyperthyroidism
- Methimazole Monitoring

A
  1. Monitor Free T4 at 4 weeks, then every 4-8 weeks (Can also add free T3)
  2. Once Free T4/T3 is normal, add TSH and monitor every 2-3 months
  3. Also taper dose by 30-50%
  4. Continue for 12-18 months
    - Taper or discontinue is TSH is normal at this time
70
Q

Long-term methimazole in Graves’ disease

A

Hyperthyroidism has less chances to recur with long term treatment

71
Q

Hyperthyroidism
- RAI Indication

A
  • Patient is unable to get surgery
  • Contraindications to ATD
  • Not planning to get pregnant
72
Q

Hyperthyroidism
- RAI Monitoring

A

Should see Euthyroidism within 6-18 weeks
- 50% chance to cause hypothyroidism after 10 years

73
Q

Hyperthyroidism
- RAI Pregnancy

A

Contraindicated in pregnancy
- Crosses placenta and destroys fetal placenta
- Defer pregnancy for 3-6 months after treatment

74
Q

Hyperthyroidism
- Surgery Indication

A
  • Symptomatic Compression
  • Large Goiter (greater than 80g)
  • Thyroid malignancy
  • Planning pregnancy 4-6 months or less
75
Q

Hyperthyroidism
- Surgery Recurrence

A

Total Thyroidectomy: 0% chance of recurrence

Subtotal Thyroidectomy: 8% chance of recurrence at 5 years

PHARM 343 (35 decks)

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