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UKMLA Prep > Thyroid > Flashcards

Thyroid Flashcards

1
Q

What are the two main thyroid hormones produced by the thyroid gland?

A

Thyroxine (T4) and Triiodothyronine (T3)

T4 is the inactive form, while T3 is the active form that regulates metabolism.

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2
Q

What is the inactive form of thyroid hormone?

A

Thyroxine (T4)

T4 acts as a prohormone and is converted to T3 in peripheral tissues.

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3
Q

What is the active form of thyroid hormone?

A

Triiodothyronine (T3)

T3 is responsible for regulating the body’s metabolism.

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4
Q

How is iodine absorbed for thyroid hormone production?

A

Iodine is absorbed from food and enters the thyroid gland via the sodium-iodine symporter.

This process is crucial for the synthesis of thyroid hormones.

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5
Q

What is thyroglobulin?

A

A protein rich in tyrosine produced by the thyroid gland

It serves as a precursor for the formation of thyroid hormones.

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6
Q

What is the process of iodine binding to thyroglobulin called?

A

Iodination

This process leads to the formation of MIT (mono-iodotyrosine) and DIT (di-iodotyrosine).

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7
Q

What does MIT + DIT equal?

A

T3

MIT represents mono-iodotyrosine and DIT represents di-iodotyrosine.

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8
Q

What does DIT + DIT equal?

A

T4

DIT is di-iodotyrosine, which combines with itself to form T4.

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9
Q

How are T3 and T4 stored in the thyroid gland?

A

In the form of colloid

They are released into the bloodstream upon stimulation by TSH.

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10
Q

What hormone does the hypothalamus release to regulate thyroid hormones?

A

Thyrotropin-Releasing Hormone (TRH)

TRH stimulates the pituitary to release TSH.

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11
Q

What is the role of Thyroid-Stimulating Hormone (TSH)?

A

Stimulates the thyroid gland to produce and release T3 and T4

TSH is crucial for the regulation of thyroid hormones.

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12
Q

What is the feedback mechanism for thyroid hormone regulation?

A

Negative feedback loop

High levels of T3 and T4 suppress TRH and TSH production, while low levels stimulate them.

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13
Q

What is one function of thyroid hormones related to metabolism?

A

Increases basal metabolic rate (BMR)

This leads to increased energy consumption.

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14
Q

How do thyroid hormones affect growth and development?

A

Essential for brain development in infants and growth in children

They play a crucial role in early life stages.

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15
Q

What effect do thyroid hormones have on the cardiovascular system?

A

Increases heart rate and cardiac output

This enhances overall cardiovascular function.

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16
Q

What is the effect of thyroid hormones on the gastrointestinal system?

A

Speeds up gut motility

This helps in digestion and nutrient absorption.

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17
Q

How do thyroid hormones influence neuromuscular function?

A

Enhances reflexes and muscle function

This is important for physical activity and coordination.

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18
Q

What role do thyroid hormones play in thermogenesis?

A

Helps maintain body temperature

This is crucial for homeostasis.

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19
Q

How do thyroid hormones travel in the blood?

A

Bound to plasma proteins

Key transport proteins include Thyroid-binding globulin (TBG) and Albumin.

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20
Q

Which forms of thyroid hormones are active in the body?

A

Free T3 and T4

Only the unbound forms exert biological effects.

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21
Q

What happens to T3 and T4 levels in hypothyroidism?

A

T3 and T4 are low, leading to a slowed metabolism.

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22
Q

What happens to TSH levels in primary hypothyroidism?

A

TSH is high.

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23
Q

What does the pituitary gland do when it senses low T3 and T4?

A

Increases TSH to stimulate the thyroid.

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24
Q

In secondary or tertiary hypothyroidism, what is the TSH level?

A

TSH is low or normal.

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25
Q

What is the TFT pattern in primary hypothyroidism?

A

TSH: High, T3/T4: Low.

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26
Q

What happens to T3 and T4 levels in hyperthyroidism?

A

T3 and T4 are high, leading to a fast metabolism.

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27
Q

What happens to TSH levels in primary hyperthyroidism?

A

TSH is low.

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28
Q

What does the pituitary gland do when it senses high T3 and T4?

A

Suppresses TSH production.

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29
Q

What is the TFT pattern in primary hyperthyroidism?

A

TSH: Low, T3/T4: High.

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30
Q

What is the active form of thyroid hormone?

A

T3.

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31
Q

What is the inactive prohormone of thyroid hormone?

A

T4.

32
Q

How do T3 and T4 levels behave in most cases of thyroid disease?

A

Both follow the same trend (both low in hypothyroidism, both high in hyperthyroidism).

33
Q

What is T3 toxicosis?

A

A rare form of hyperthyroidism where only T3 is high.

34
Q

In primary hypothyroidism, what is the condition of the thyroid gland?

A

Underactive.

35
Q

In secondary hypothyroidism, what is the problem?

A

Problem in the pituitary gland (less TSH).

36
Q

What is the condition of the thyroid gland in primary hyperthyroidism?

A

Overproduces hormones.

37
Q

What is the rare condition associated with secondary hyperthyroidism?

A

TSH-secreting pituitary adenoma.

38
Q
A
39
Q
A
40
Q

What is the main goal in the management of hypothyroidism?

A

To replace the missing thyroid hormones

41
Q

What is the first-line treatment for hypothyroidism?

A

Levothyroxine (T4)

42
Q

What is the starting dose of Levothyroxine for hypothyroidism?

A

Usually 50–100 mcg once daily

43
Q

How often should the dose of Levothyroxine be adjusted based on TSH levels?

A

Every 6–8 weeks

44
Q

What is the target TSH level range for managing hypothyroidism?

A

Typically 0.4–4.0 mU/L

45
Q

How often should TFTs be monitored once stable in hypothyroidism management?

A

Every 6–12 months

46
Q

What special consideration should be taken for pregnant patients with hypothyroidism?

A

Levothyroxine requirements increase during pregnancy; close monitoring is essential

47
Q

What starting dose of Levothyroxine is recommended for the elderly or those with cardiovascular disease?

A

Start with a lower dose (e.g., 25 mcg/day)

48
Q

What is the main goal in the management of hyperthyroidism?

A

To reduce excess thyroid hormone production and address the underlying cause

49
Q

What are the first-line treatments for hyperthyroidism?

A

Antithyroid drugs and beta-blockers

50
Q

What is the most commonly used antithyroid drug?

A

Carbimazole

51
Q

What is the starting dose for Carbimazole?

A

15–40 mg daily

52
Q

What alternative antithyroid drug is used in the first trimester of pregnancy?

A

Propylthiouracil (PTU)

53
Q

What is a ‘block and replace’ regimen in hyperthyroidism management?

A

High-dose carbimazole is used to suppress the thyroid, followed by levothyroxine to normalize hormone levels

54
Q

What is the purpose of beta-blockers in hyperthyroidism management?

A

Used for symptom control (e.g., tachycardia, tremor, anxiety)

55
Q

What is an example of a beta-blocker used in hyperthyroidism?

A

Propranolol 40–80 mg TDS

56
Q

What is the definitive treatment for hyperthyroidism?

A

Radioiodine therapy and surgery (thyroidectomy)

57
Q

What is the mechanism of radioiodine therapy?

A

A single dose of radioactive iodine to destroy overactive thyroid tissue

58
Q

What are the risks associated with thyroidectomy?

A

Hypothyroidism, hypoparathyroidism, and recurrent laryngeal nerve injury

59
Q

What special consideration should be taken for Graves’ disease?

A

May require long-term carbimazole or definitive treatment (radioiodine or surgery)

60
Q

What is the management for thyroid storm?

A

High-dose beta-blockers, high-dose carbimazole/PTU, steroids, supportive care

61
Q

What is the treatment for myxedema coma?

A

IV levothyroxine or liothyronine (T3) and IV hydrocortisone if adrenal insufficiency suspected

62
Q

Fill in the blank: The starting dose of Carbimazole is _______.

A

15–40 mg daily

63
Q

True or False: Levothyroxine should not be monitored after stabilization in hypothyroidism management.

A

False

64
Q

What supportive care is provided in the management of myxedema coma?

A

Warming, fluids, correction of electrolytes

65
Q
A
66
Q

What is Graves’ disease?

A

An autoimmune thyroid disease where the body produces IgG antibodies to the TSH receptor

It is the most common cause of thyrotoxicosis and is typically seen in women aged 30-50 years.

67
Q

What are typical features of thyrotoxicosis?

A

Increased metabolic rate, weight loss, heat intolerance, palpitations, anxiety

These features are common across various causes of thyrotoxicosis.

68
Q

What specific eye signs are seen in Graves’ disease?

A

Exophthalmos, ophthalmoplegia

Eye signs are present in about 30% of patients.

69
Q

What is pretibial myxoedema?

A

A specific sign of Graves’ disease characterized by swelling and thickening of the skin over the shins

It is one of the unique features of Graves’ disease.

70
Q

What is thyroid acropachy?

A

A triad of symptoms including digital clubbing, soft tissue swelling of the hands and feet, periosteal new bone formation

This condition is associated with Graves’ disease.

71
Q

What are TSH receptor stimulating antibodies?

A

Antibodies found in 90% of patients with Graves’ disease that stimulate the TSH receptor

These are critical in the pathogenesis of the disease.

72
Q

What percentage of patients with Graves’ disease have anti-thyroid peroxidase antibodies?

A

75%

These antibodies are also present in other autoimmune thyroid diseases.

73
Q

What does thyroid scintigraphy show in Graves’ disease?

A

Diffuse, homogenous, increased uptake of radioactive iodine

This finding helps to differentiate Graves’ disease from other causes of thyrotoxicosis.

74
Q

Fill in the blank: Graves’ disease is the most common cause of _______.

A

thyrotoxicosis

75
Q

True or False: Ophthalmoplegia is a common feature of all causes of thyrotoxicosis.

A

False

Ophthalmoplegia is specific to Graves’ disease.

UKMLA Prep (46 decks)

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