Met 2, Week 2 > 9 - Thyroid > Flashcards

9 - Thyroid Flashcards

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1
Q

What is the common name for Liothyronine?

A

T3 (tri-iodothyronine).

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2
Q

What is the common name for Levothyroxine?

A

T4 (tetra-iodothyronine).

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3
Q

What is the approximate weight of the thyroid gland?

A

15-20g.

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4
Q

From which embryological structure does the thyroid gland descend?

A

The foramen cecum.

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5
Q

The path of the thyroid gland’s embryological descent is along the _____ duct.

A

Thyroglossal

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6
Q

What is the name of the functional unit of the thyroid gland?

A

The thyroid follicle.

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7
Q

What shape do thyroid follicular cells adopt when they are active?

A

Columnar.

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8
Q

What is the gelatinous substance stored within thyroid follicles called?

A

Colloid.

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9
Q

What is the precursor amino acid for thyroid hormones?

A

Tyrosine.

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10
Q

What does MIT stand for in the context of thyroid hormone synthesis?

A

Mono-iodotyrosine.

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11
Q

What does DIT stand for in the context of thyroid hormone synthesis?

A

Di-iodotyrosine.

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12
Q

Which transporter is responsible for moving iodide ions into the thyroid follicular cell from the blood?

A

The Sodium-Iodide Symporter (NIS).

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13
Q
A
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14
Q

What is the ion stoichiometry of the Sodium-Iodide Symporter (NIS)?

A

2 Na+ ions for every 1 I- ion.

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15
Q

What hormone, released from the hypothalamus, initiates the thyroid hormone regulation cascade?

A

Thyrotropin-releasing hormone (TRH).

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16
Q

What hormone, released from the pituitary gland, stimulates the thyroid gland?

A

Thyroid-stimulating hormone (TSH).

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17
Q

What is the primary protein that transports thyroid hormones in the blood?

A

Thyroid Binding Globulin (TBG).

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18
Q

Name two transport proteins for thyroid hormones other than Thyroid Binding Globulin.

A

Albumin and transthyretin.

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19
Q

Which specific transporters, belonging to the monocarboxylate transporter family, are responsible for thyroid hormone uptake into cells?

A

MCT8 and MCT10.

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20
Q

What class of enzymes is responsible for converting T4 to the more active T3 in peripheral tissues?

A

Deiodinases.

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21
Q

Which deiodinase is primarily responsible for producing plasma T3 and is found in the liver, kidney, and muscle?

A

Type 1 deiodinase (D1).

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22
Q

Which deiodinase is primarily responsible for local T3 production and is found in the brain, pituitary, and brown fat?

A

Type 2 deiodinase (D2).

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23
Q

What is the main function of Type 3 deiodinase (D3)?

A

T3 degradation.

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24
Q

How does hypothyroidism affect the regulation of Type 2 deiodinase (D2)?

A

It is upregulated.

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25
How does hyperthyroidism affect the regulation of Type 1 deiodinase (D1)?
It is upregulated.
26
To what intracellular structure do thyroid hormones bind to regulate gene expression?
The Thyroid Hormone Receptor (TR).
27
The thyroid hormone receptor binds to a specific DNA sequence known as the _____.
Thyroid Response Element (TRE)
28
What are the three main levels of regulation of thyroid hormone action?
The HPT axis, regulation of hormone uptake transporters, and regulation of local deiodinase levels/receptor expression.
29
List four major physiological systems affected by thyroid hormones.
Metabolism, growth, cardiovascular system, and the central nervous system (CNS).
30
What is the term for a state of excess thyroid hormone in the body, regardless of the source?
Thyrotoxicosis.
31
What is a common cardiac arrhythmia seen in approximately 20% of patients with thyrotoxicosis?
Atrial fibrillation (AF).
32
How do thyroid hormones affect the Basal Metabolic Rate (BMR) in hyperthyroidism?
They cause an increased BMR.
33
What is the term for a symptom of hyperthyroidism characterised by an inability to cope with warm temperatures?
Heat intolerance.
34
What effect does hyperthyroidism have on protein and lipid stores?
It causes protein and lipid degradation, leading to weight loss and myopathy.
35
What is the effect of hyperthyroidism on bone turnover?
It causes accelerated osteoclast activity, leading to hypercalcemia and osteoporosis.
36
What is the most common cause of hyperthyroidism?
Graves' disease.
37
List three risk factors for Graves' disease.
HLA Status, infection, stress, and female sex.
38
What is the pathophysiology of Graves' eye disease?
Activation of retro-orbital fibrocytes.
39
A thyroid uptake scan showing multiple areas of high uptake is characteristic of what condition?
Toxic Multinodular Goitre.
40
A thyroid uptake scan showing a single 'hot' nodule with suppression of the rest of the gland is characteristic of what condition?
Toxic Adenoma.
41
What are the typical findings for TSH, T4, and T3 levels in primary hyperthyroidism?
Suppressed TSH with elevated T4 and T3.
42
What is the class of drugs used to block the synthesis of thyroid hormones?
Thionamides.
43
Name two specific thionamide drugs used to treat hyperthyroidism.
Carbimazole and Propylthiouracil.
44
What isotope of iodine is used for the radioactive iodine treatment of hyperthyroidism?
Iodine-131 (I-131).
45
What is the term for the surgical removal of the thyroid gland?
Thyroidectomy.
46
What cardiovascular sign is characteristic of hypothyroidism?
Sinus bradycardia.
47
How does hypothyroidism affect LDL cholesterol levels?
It causes LDL cholesterol levels to increase.
48
What gastrointestinal symptom is common in hypothyroidism?
Constipation.
49
What is the consequence of severe hypothyroidism during foetal development on the brain?
Impaired foetal brain development (cretinism).
50
In hypothyroidism, the deep tendon reflexes are characteristically described as _____.
Slow relaxing
51
What type of anaemia is typically seen in hypothyroidism?
Normochromic normocytic anaemia.
52
How does hypothyroidism affect the basal metabolic rate (BMR)?
It causes a reduced BMR.
53
What is the most common cause of hypothyroidism in iodine-sufficient areas?
Hashimoto's disease (autoimmune thyroiditis).
54
A goitre caused by insufficient dietary iodine is known as an _____ goitre.
Endemic
55
Which medication, used in psychiatry, is a known cause of hypothyroidism?
Lithium.
56
What is the recommended daily iodine intake for pregnant and lactating women?
250μg per day.
57
What is the term for severe hypothyroidism in infancy leading to developmental abnormalities?
Cretinism.
58
What are the typical findings for TSH and T4 levels in primary hypothyroidism?
High TSH and low T4.
59
What is the standard medication used for thyroid hormone replacement in hypothyroidism?
Levothyroxine (T4).
60
What is the name for desiccated animal thyroid extract sometimes used to treat hypothyroidism?
Armour thyroid.
61
In hyperthyroidism, what nail deformity can be observed?
Plummer's nails (onycholysis).
62
What is the name of the skin condition, a specific sign of Graves' disease, characterised by localised oedema on the shins?
Pretibial myxoedema.
63
In the context of autoimmune thyroid disease (AITD), hyperthyroidism can be associated with which type of anaemia?
Pernicious anaemia (B12 deficiency).
64
Name a reproductive system effect of hyperthyroidism in women.
Oligomenorrhoea (infrequent menstrual periods).
65
Name a reproductive system effect of hyperthyroidism in men.
Gynaecomastia or erectile dysfunction.
66
Which medication, used for cardiac arrhythmias, can cause thyrotoxicosis?
Amiodarone.
67
A rare cause of thyrotoxicosis is a teratoma of the ovary that contains thyroid tissue, known as _____.
Struma ovarii
68
A pituitary adenoma that secretes TSH, causing hyperthyroidism, is called a _____.
TSHoma
69
How does hypothyroidism impact renal function?
It can cause a reduced Glomerular Filtration Rate (GFR).
70
What effect can hypothyroidism have on puberty?
It can cause delayed puberty.
71
The coupling of one MIT and one DIT molecule forms which thyroid hormone?
T3 (tri-iodothyronine).
72
The coupling of two DIT molecules forms which thyroid hormone?
T4 (tetra-iodothyronine).
73
How is TSH stimulation of the thyroid follicular cell mediated intracellularly?
Via the cAMP second messenger system.
74
Which deiodinase has T4 as its preferred substrate over T3?
Type 2 deiodinase (D2).
75
Which deiodinase prefers rT3 as a substrate over T4?
Type 1 deiodinase (D1).
76
Where in the cell is Type 2 deiodinase typically located?
On the endoplasmic reticulum (ER) near the nucleus.
77
Where in the cell is Type 1 deiodinase typically located?
On the plasma membrane.
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