Phase 1b - Endocrinology > Hyperthyroidism > Flashcards

Hyperthyroidism Flashcards

-> Function of endocrine glands: Summarise the function of the key endocrine glands, including the synthesis, regulation and physiological effects of their hormones. -> Endocrine disorders: Describe the clinical features and treatment options of endocrine disorders. (52 cards)

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1
Q

Which endocrine cells release TSH?

A
  • Thyrotrophs within the anterior pituitary gland
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2
Q

Which cells respond to TSH?

A
  • Follicular cells of the thyroid gland
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3
Q

How is iodine pumped into follicular cell of the thyroid gland?

A
  • Sodium-iodine symporter (secondary active transport)
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4
Q

How is iodide pumped from the follicle into the colloid?

A
  • Pendrin pumps within the apical membrane
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5
Q

How is iodine activated into iodide?

A
  • Under the action of thyroid peroxidase in the presence of hydrogen peroxide
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6
Q

Where does iodination occur within the thyroid gland?

A
  • Within the colloid
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7
Q

What are the two direct products of iodination of thyroglobulin within the colloid?

A
  • Monoiodotyrosine (MIT) or Diiodotyrosine (DIT) molecules
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8
Q

Which thyroid pro-hormone is iodinated?

A
  • Thyroglobulin
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9
Q

Which thyroglobulin residues are iodinated?

A
  • Tyrosine residues
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10
Q

How is triiodothyronine (T3) formed?

A
  • Coupling of MIT and DIT
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11
Q

How is tetraiodothyronine / thyroxine (T4) formed?

A
  • Coupling of DIT molecules
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12
Q

Which thyroid hormone is active?

A
  • T3

Tetraiodothyronine (Thyroxine, T4) is a prohormone converted by deiodinase enzyme into the more active metabolite triiodothyronine (T3)

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13
Q

Which structures are directly inhibited by thyroxine (fT4) via negative feedback mechanisms?

A
  • Anterior pituitary gland (thyrotrophs)
  • Hypothalamic neurones (secreting TRH)
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14
Q

What is the effect of thyroxine (fT4) on the heart rate?

A
  • Sensitives beta adrenoreceptors to ambient levels of adrenaline and noradrenaline
    • This increases the heart rate ( tachycardia and tremor in hands) → Lid lag
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15
Q

What are the common forms of hyperthyroidism (4)?

A
  • Grave’s Disease (Autoimmune Disease)
  • Plummer’s Disease (Non-Autoimmune Disease)
  • Viral (de Quervain’s) thyroiditis
  • Post partum thyroiditis
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16
Q

What is the pathophysiology of Grave’s disease (autoimmuune hyperthyroidism)?

A
  1. TSH Immunoglobulins binds to TSH receptors in the thyroid gland
  2. ​​Stimulation of TSH receptors subsequently result in smooth goitre formation and hyperthyroidism
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17
Q

What are the clinical signs of Grave’s disease (3)?

A
  • Elevated fT4
  • Elevated fT3
  • Insufficient TSH
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18
Q

What are the clinical features of Grave’s disease (10)?

A
  • Respiration, facial flushing
  • Muscle wasting
  • Shortness of breath
  • Heat intolerance
  • Weight loss - despite increased appetite
  • Localised myxoedema
  • Tremor
  • Sweating
  • Palpitations
  • Exophthalmos (proptosis)

Antibodies bind to muscles behind the eye and cause exophthalmos

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19
Q

What is pretibial myxoedema?

A
  • The swelling that occurs on the shins (legs) of patients with Grave’s disease: growth of soft tissue

Not to be confused with myxoedema = hypothyroidism

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20
Q

What type of goitre is shown in a patient with Plummer’s disease (non-autoimmuune hyperthyroidism)?

A
  • Toxic nodular goitre
    • ​Benign nodules of the thyroid gland (not autoimmune associated)
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21
Q

What are the clinical signs of Plummer’s disease (3)?

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A
  • Elevated fT4
  • Elevated fT3
  • Insufficient TSH
22
Q

What are the clinical features of Plummer’s disease (8)?

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A
  • Weight loss - despite increased appetite
  • Shortness of breath
  • Palpitations
  • Tachycardia
  • Sweating
  • Heat intolerance
  • Diarrhoea
  • Lid lag and other sympathetic features
23
Q

What are the four main features of viral (de Quervain’s) thyroiditis?

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A
  • Painful dysphagia
  • Hyperthyroidism (The thyroid gland is tender and palpable)
  • Pyrexia (fever)
  • Thyroid inflammation
24
Q

How is hyperthyroidism induced in individuals with viral (de Quervain’s) thyroiditis?

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A
  • Round follicle is damaged, subsequently causing stored thyroxine within the colloid to be released
25
Describe the pattern of iodine uptake in an individual with viral (de Quervain’s) thyroiditis.
* There is **no iodine uptake** as the thyroid gland stops making thyroxine
26
How is hypothyroidism caused in individuals with viral (de Quervain’s) thyroiditis?
* Four weeks upon the onset of viral thyroiditis, **stored thyroxine is depleted**
27
How is viral (de Quervain’s) thyroiditis managed?
* A further month after hypothyroidism occurs, resolution occurs (like in all viral diseases) * Patient then becomes **euthyroid** again.
28
What type thyroid scan is conducted to identify the type of goitre in hyperthyroidism (Grave's or Plummer's)?
* **Iodine-123** scan
29
Which radioisotope is administered for a thyroid scan?
* Tc-99
30
How is Grave's disease diagnosed (distinguished from Plummer's disease) (2)?
* Positive **anti-TSH** **receptor** antibody blood test * Radioactive iodine uptake test ## Footnote Diffuse goitre of moderate size and uniform radioiodine uptake
31
Which part of the thyroid gland uptakes iodine-123 in Plummer's disease?
* The **toxic nodular goitre** * The inactive thyroid gland is suppressed due to the adenoma.
32
What are the long term treatment options of hyperthyroidism (3)?
* **Surgery** * **Radioiodine** * **Anti-thyroid drugs**
33
What are the associated risks with a thyroidectomy?
* Risk of **voice change** * Risk of also **losing parathyroid glands** * **Scar** * **Anaesthetic**
34
Which nerve is at risk of damage during a thyroidectomy?
* The **recurrent laryngeal nerve**
35
Which isotope is used in radioiodine?
* **Iodine 131** * Emits radiation for 10 days therefore avoid pregnant individuals
36
What are the 3 main classes of drugs used in the treatment of hyperthyroidism?
1. Thionamides 1. Potassium Iodide 1. Beta-blockers
37
How long should anti-thyroid drugs typically be prescribed for?
18 months
38
What class of drug is the main anti-thyroid?
* **Thionamides** * Propylthiouracil (PTU) * Carbimazole (CBZ)
39
What is the mechanism of action of thionamides?
* **Inhibition of thyroid peroxidase and peroxidase transaminase**, therefore **reduce** iodine activation and iodination of thyroglobulin into **MIT & DIT**
40
Which enzyme is inhibited by thionamides?
Thyroid peroxidase
41
Why does it take 3-4 weeks for the clinical effects of anti-thyroid hormones to become apparrent?
* There is a months **store of thyroxine**
42
Which co-drug is prescribed alongside thionamides? Why?
* **Propanolol** rapidly reduces **tremors & tachycardia**
43
What are the unwanted actions of thinamides (2)?
* **Agranulocytosis** (reduction in neutrophils) - neutropenia increases risk of sepsis * **Rashes** (common) ## Footnote Agranulocytosis is reversed witht he withdrawl of the drug
44
Which drug should be pre-operatively administered in hyperthyroid patients?
Potassium Iodide - induces Wolff-Chaikoff effect (10 days)
45
What effect does KI have in hyperthyroid patients (3)?
* **Inhibits hydrogen peroxide** generation and thyroid peroxidase * **Reduces vascularity and size of gland** (atrophy of thyroid gland) * **Inhibits the iodination of thyroglobulin** by inducing the Wolff-Chaikoff effect
46
Which effect demonstrates the auto-regulatory function of iodine control?
* Wolff-Chaikoff effect
47
What is the Wolff-Chaikoff effect?
* An **autoregulatory function**, whereby an **excess ingestion of iodine inhibits thyroid peroxidase activity** and thus **reducing iodothyronine production** within thyroid follicular cells, **independent from the serum-level of thyroid-stimulating hormone (TSH)**
48
What purpose do beta-blockers have in terms of hyperthyroidism treatment?
* Alleviate the symptoms concerned with **arrhythmia**
49
What is the role performed by beta blockers in thyrotoxicosis?
* Reduces heart rate and beta adrenoreceptor sensitivity
50
What are the main clinical features of a thyroid storm (5)?
* **Hyperpyrexia** \> 41 oC * Accelerated **tachycardia** / arrhythmia * **Cardiac failure** * **Delirium** / frank psychosis * Hepatocellular dysfunction; **jaundice**
51
What are the main treatment options for a thyroid storm (3)?
* Thyroidectomy * Radioiodine * Drugs
52
What are the short term drug options of a thyroid storm (2)?
* Beta - blockers * Thionamides
Phase 1b - Endocrinology
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