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Gastrointestinal Block > Thyroid disorders > Flashcards

Thyroid disorders Flashcards

1
Q

Explain the process of Thyroid Hormone Synthesis

A

1) Organification of iodide: Iodide → Iodine → condensed onto tyrosine residues → mono or di-iodinated tyrosine
2) Coupling reaction: 2 DIT molecules → T4
3) Release of the T3 and T4 from the thyroid gland
4) Major production of T3 occurs outside of the thyroid gland by peripheral conversion from T4

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2
Q

Explain the hypothalamo-pituitary-thyroid axis

A
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3
Q

Are primary or secondary disorders of thyroid gland more common?

A

Primary

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4
Q

Are thyroid diseases more common in women or men

A

Women

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5
Q

What are autoimmune thyroid disorders commonly associated with?

A

Other autoimmune diseases e.g. T1 DM, autoimmune adrenal insufficiency

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6
Q

Is T3 or T4 more more biologically active

A

T3

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7
Q

What is Hyperthyroidism?

A

Over-production of thyroid hormone by the thyroid gland

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8
Q

What is Thyrotoxicosis?

A

Abnormal and excessive quantity of thyroid hormone in the body

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9
Q

Most common cause of Hyperthyroidism?

List 4 other common causes of thyrotoxicosis

A

Graves’ Disease ☆

  1. Iatrogenic,
  2. Toxic adenoma,
  3. Toxic multinodular goitre
  4. Thyroiditis
  5. Iodide excess
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10
Q

What is Graves disease? Incl the pathophysiology

A

Autoimmune condition where TSH receptor antibodies cause a primary hyperthyroidism.

These TSH receptor antibodies (TSHRAb) mimic TSH and stimulate TSH receptors on the thyroid

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11
Q

What is subclinical hyperthyroidism?

A

Low levels of TSH but normal levels of T3 and T4

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12
Q

List 4 symptoms of hyperthyroidism

A
  1. Anxiety and irritability
  2. Weakness and fatigue
  3. Palpitations
  4. Sweating and heat intolerance
  5. Dyspnoea
  6. Frequent loose stools (hyperdefecation)
  7. Insomnia
  8. Poor concentration
  9. Menstrual abnormalities and sexual dysfunction
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13
Q

List 4 signs of hyperthyroidism

A
  1. Weight loss
  2. Proximal myopathy
  3. Tachycardia, arrythmias
  4. Warm, moist skin
  5. Tremor
  6. Eye conditions (stare, lid lag, lid retraction)
  7. Emotional lability
  8. Hyperactive deep tendon reflexes with shortened relaxation time
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14
Q

What is a Thyroid storm?

A

Exaggerated typical signs and symptoms, fever, jaundice, changes in neurologic function

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15
Q

Clinical features/presentation specific to Graves disease

A
  1. Diffuse goitre (without nodules)
  2. Graves eye disease
  3. Bilateral exophthalmos
  4. Pretibial myxoedema
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16
Q

Pathophysiology behind Graves’ Ophthalmopathy?

A

Antibodies to TSH receptor also target retroorbital tissues

  • T-cell inflammatory infiltrate → fibroblast growth
  • Severe: exposure keratopathy, diplopia, com-pressive optic neuropathy

Strong link with tobacco and seen in 50% of Graves Disease

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17
Q

Pathophysiology behind Graves’ Myxedema (thyroid dermopathy)

A

Activation of fibroblasts → increased hyaluronic acid and chondroitin sulfate

Asymmetric, raised, firm, pink-to-purple, brown plaques of nonpitting edema

Occurs In <5% of Graves disease

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18
Q

What is Thyroid acropachy?

List the 3 characteristic findings on imaging which comprise this

A

Rare complication of autoimmune thyroid disease

  1. Digital clubbing
  2. Soft tissue swelling of hands and feet
  3. Periosteal bone formation

Occurs in 0.1-1 % and almost always in patients with myxedema and ophthalmopathy

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19
Q

Laboratory findings indicative of primary hyperthyroidism?

A

Suppressed TSH (<0.05 uU/ml)

Elevated Free T4 and/or Free T3

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20
Q

Ddx in a patient with hyperthyroidism for the follow values of T3:T4

  • T3:T4 > 20
  • T3:T4 < 20
A

T3:T4 > 20:

  • Graves’ Disease
  • Toxic MN Goiter

T3:T4 < 20:

  • Non-thyroid illness
  • Thyroiditis
  • Exogenous thyroxine
21
Q

List 3 other investigations for hyperthyroidism

A
  1. Thyroid radioiodine uptake
  2. TSH receptor antibodies: Grave’s
  3. US thyroid: hypoechogenic in untreated diffuse toxic goitre
22
Q

What would iodine uptake show on nuclear scintigraphy for the following:

  1. Toxic multinodular
  2. Graves
  3. De Quervain’s thyroiditis
A
  1. TMG: Patchy uptake
  2. Graves: diffuse, homogenous, increased uptake
  3. DQ thyroiditis: globally reduced uptake of iodine-131
23
Q

List 4 complications of hyperthyroidism

A
  1. Atrial Fibrillation
  2. Osteoporosis
  3. Heart failure
  4. Thyroid Storm
24
Q

List 4 treatments of thyrotoxicois?

A
  1. Antithyroid medications: Carbimazole and Propylthiouracil
  2. β- blockers for symptom control (Propranolol preferred)
  3. Radioactive iodine
  4. Surgery
25
Q

List 2 dangers/ side effects of Antithyroid medications

A

Carbimazole and Propylthiouracil can cause Agranulocytosis, and or hepatotoxicity (PTU)

26
Q

What is hypothyroidism?

A

Inadequate output of thyroid hormones by the thyroid gland

27
Q

List 4 populations at risk of hypothyroidism

A
  1. Women
  2. History of Graves disease or postpartum thyroid dysfunction
  3. Elderly
  4. Other autoimmune disease
  5. Family history of thyroid disease, pernicious anemia, type I DM
28
Q

Is primary or secondary hypothyroidism more common?

What is the difference between these

A

1o → Thyroid gland insufficiency (more common)

2o → Pituitary pathology

29
Q

What defines subclinical hypothyroidism?

A

Normal free T4 concentration in the presence of an elevated TSH concentration

30
Q

What is the treatment of choice for hypothyroidism?

A

Levothyroxine (needs to be titrated)

31
Q

List 4 causes of Hypothyroidism

A
  1. Hashimoto’s thyroiditis
  2. Thyroiditis
  3. Congenital hypothyroidism
  4. Drug induced
  5. Post radiation
  6. Thyroid surgery
32
Q

List 4 clinical features of hypothyroidism

A
  1. Weight gain
  2. Fatigue
  3. Dry skin
  4. Coarse hair and hair loss
  5. Fluid retention (oedema, pleural effusions, ascites)
  6. Heavy or irregular periods
  7. Constipation
33
Q

What is a Myxedema coma?

How does it present?

A

Medical emergency - end stage of untreated/insufficiently treated hypothyroidism

Presents with:

  1. hypothermic
  2. hypotensive
  3. hypoventilation
  4. bradycardic
  5. Impaired sensorium
34
Q

What is cretinism and why does it occur?

List 3 clinical features

A

Lack of thyroxine from birth or before birth (severe and irreparable)

From lack of thyroid gland or lack of iodine in mother

  1. Mental defects
  2. Stunted growth
  3. Reduced growth and function of many organs
35
Q

Typical clinical picture of a Myxedema Coma?

A
  1. Elderly obese female
  2. Becoming increasingly withdrawn, lethargic, sleepy and confused
  3. Slips into a coma
36
Q

List 4 physical findings of Myxedema Coma

A
  1. Comatose or semi comatose
  2. Hypothyroid features: dry coarse skin, hoarse voice, thin dry hair
  3. Delayed reflex relaxation time
  4. Hypothermia
  5. Pericardial, pleural effusions, ascites
37
Q

Typical history of a Myxedema Coma?

A
  1. Previous thyroid surgery
  2. Radioiodine
  3. Default thyroid hormone therapy
38
Q

List 4 things which may precipitate a Myxedematous Coma

A
  1. Infections
  2. Trauma (incl surgery)
  3. Exposure to cold
  4. CVS problems
  5. Drugs
39
Q

Management of Myxedema?

A
  1. ICU admission - ventilatory support and IV meds
  2. Parenteral thyroxine
  3. Electrolytes - water restriction for hyponatremia, avoid fluid overload
  4. Avoid sedation
  5. Glucocorticoids - Hydrocortisone
40
Q

List 4 factors which may reduce levothyroxine effectiveness

A
  1. Malabsorption Syndromes ie. celiac disease
  2. Drugs that ↑ clearance ie. rifampin
  3. Factors that ↓ T4 to T3 clearance ie. amiodarone
  4. ↓absorption ie. ferrous sulfate
  5. Other Mechanisms ie. sertraline
41
Q

What is Hashimoto’s Thyroiditis?

A

Autoimmune inflammation of the thyroid gland.

Initially it causes a goitre after which there is atrophy of the thyroid gland.

42
Q

List 2 antibodies which are associated with Hashimoto’s Thyroiditis

A
  1. antithyroid peroxidase (anti-TPO) antibodies
  2. antithyroglobulin antibodies
43
Q

a) What is the most common cause of hypothyroidism in the developed word
b) What is the most common cause of hypothyroidism in the developing world

A

a) Hashimoto’s Thyroiditis
b) Iodine Deficiency

44
Q

All treatments for hyperthyroidism have potential to cause hypothyroidism, list 4 of these

A
  1. Carbimazole
  2. Propylthiouracil
  3. Radioactive iodine
  4. Thyroid surgery
45
Q

List 2 other medications which can cause hyperthyroidism

A
  1. Lithium - inhibits production of thyroid hormones in the gland, can cause a goitre and hypothyroidism
  2. Amiodarone - interferes with thyroid hormone production and metabolism, can cause both hypothyroidism and thyrotoxicosis
46
Q

What findings on a thyroid function test would be indicative of a primary vs secondary cause of hypothyroidism?

A

1o → low T3 & T4, high TSH

2o → low TSH, low T3 & T4

47
Q

What is secondary hypothyroidism?

A

Where the pituitary gland is failing to produce enough TSH.

Often associated with a lack of other pituitary hormones ie. ACTH - known as ‘hypopituitarism’

48
Q

List 4 causes of secondary hypothyroidism

A
  1. Tumours
  2. Infection
  3. Vascular (e.g. Sheehan Syndrome)
  4. Radiation
49
Q

What is Sheehan Syndrome?

A

Hypopituitarism caused by ischemic necrosis due to blood loss and hypovolemic shock during and after childbirth

Also known as postpartum pituitary gland necrosis

Gastrointestinal Block (26 decks)

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