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Endocrinology > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

How many lobes comprise the thyroid gland?

A

2

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2
Q

What connects the two lobes?

A

Isthmus

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3
Q

What is the pyramidal lobe?

A

Embryological remnant
Extra lobe
In 20-30% of people

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4
Q

What cells make up the thyroid gland?

A

Follicular cells
Follicles
Parafollicular cells

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5
Q

Where are the parathyroid glands?

A

Embedded in the thyroid

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6
Q

Why can surgical procedures on the thyroid be so dangerous?

A

Near many important structures
e.g. Common Carotid
Internal Jugular

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7
Q

Where is the left recurrent laryngeal nerve?

What does it supply?

A

Runs close to the thyroid
Supplies vocal cords
Damage can interfere with your voice

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8
Q

What are the superior and inferior parathyroid glands important in?

A

Calcium metabolism

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9
Q

Describe the embryology of the thyroid gland

A 
Base of the tongue
Thyroglossal duct develops
Divides into 2 lobes
Duct disappears leaving foramen caecum
Final position by week 7 of gestation
Gland then develops
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10
Q

What is colloid?

A

Sticky music found in the middle of the follicle cells

Where thyroid hormone is made

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11
Q

How is thyroid hormone made?

A

TSH secreted from anterior pituitary and binds to TSH Receptor on follicular cell membrane
Arrival of iodide ions, enter follicular cells via Na/I transporter
Iodide enters colloid
Oxidised to make Iodine
TSH activates thyroperoxidase enzyme catalyses (with H2o2) the iodination reactions in colloid
Thyroglobulin (prohormone) produced, has tyrosine residues within its structure
Iodine sticks to tyrosine residues
Produces mono/di iodotyrosine
Couple to give T3 + T4
Bound to thyroglobulin move to follicular cell
Released from thyroglobulin
Released into capillaries

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12
Q

What is the chemical name for T3?

A

3,5,3’-Tri-IodoThyronine

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13
Q

What is the chemical name for T4?

A

3,5,3’,5’-Tetra-IodoThyronine

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14
Q

What is T4 more commonly known as?

A

Thyroxine

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15
Q

What is T3?

A

Bioactive form
Provides almost all activity in target cells
Half life 2 days

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16
Q

What are the main features of T4?

A

Prohormone converted by deiodinase enzyme into the more active metabolite T3
Half life 7-9 days

17
Q

What are the percentages of organ for T3?

A

80% from deionisation of T4

20% from direct thyroidal secretion

18
Q

How is thyroid transported?

A 
Mostly bound to plasma proteins
1. TBG (Thyroid binding globulin)
2. Albumin
3. Prealbumin
Less than 1% is unbound and active
19
Q

What are their effects on gene expression?

A

Enter nucleus and binds to THR receptor

20
Q

What are the action of Thyroid hormone?

A

Foetal growth and development (in particular the CNS)
Increases basal metabolic rate
Protein, carbohydrate and fat metabolism
Potentiate actions of catecholamines (e.g. tachycardia, lipolysis)
Effects on the GI, CNS and Reproductive systems

21
Q

What is cretinism?

A

Untreated congenital hypothyroidism

Born with no thyroid hormone

22
Q

Why is cretinism not seen much anymore?

A

Tested for in the heel prick test
Measure TSH levels
If high, baby is not producing enough thyroid hormone

23
Q

What controls thyroid hormone production?

A

Hypothalamus produces TRH (Thyrotropin releasing hormone)
Enters anterior pituitary
Stimulates thyrotroph cells to release TSH
Enters systemic circulation and arrives at the thyroid
Negative feedback loop

24
Q

What can thyrotropin also be known as?

A

TSH

Thyroid Stimulating Hormone

25
Q

What can patients with an overactive thyroid be given?

A

Potassium iodide

Switches of thyroid hormone production

26
Q

What is more common hyper/hypothyroidism?

A

The same

27
Q

Are men or women more commonly affected?

A

Women

4:1

28
Q

What results from hypothyroidism?

A

Thyroxine levels decline

TSH levels climb- want to stimulate production of T3 and T4

29
Q

What can cause hypothyroidism?

A

No thyroid gland
Autoimmune disorders
Hashimoto’s and Graves’ disease
The presence of one autoimmune disease increase the chance of contracting another

30
Q

What are the symptoms/ signs of hypothyroidism?

A 
Fatigue
Depression 
Deepening voice
Cold intolerance
Weight gain with reduced appetite
Constipation
Bradycardia
Eventual myxoedema coma
Low libido
Period issues
31
Q

What is the treatment methods for hypothyroidism?

A

Levothyroxine

If taken completely restores normal function

32
Q

What is the treatment method for hyperthyroidism?

A

A blocker is given

Levothyroxine got give normal levels

33
Q

What’s the deal with dosing?

A

Adjusted to TSH (aim to get in normal range)
Common does 100 micrograms
Most commonly administered orally

34
Q

Potential complications?

A

Weight loss
Headaches
Tachycardia
Heart Attack

35
Q

What’s the deal with combine thyroid hormone replacement?

A

You do not need T4

Some reports showing that psychologically people fell better

36
Q

What results from hyperthyroidism?

A

Thyroxine levels rise

TSH levels drop

37
Q

What can cause hyperthyroidism?

A

Graves’ disease
Toxic multi nodular goitre
Solitary toxic nodule

38
Q

What are the main features of Graves’ disease?

A

Autoimmune disease
Antibodies bind to an stimulate TSH receptor in the thyroid
Completely disrupts negative feedback loop
- Smooth goitre
(diffuse enlargement and engorgement of the thyroid gland)

Other antibodies bind to muscle behind the eye can causes bulging (Exopthalmos)

Others stimulate growth of soft tissues of shins
(Pretibial myxoedma)

39
Q

What are the symptoms and signs of Hyperthyroidism?

A 
Heat intolerance
Weight loss with increase appetite
Myopathy
Mood swings
Diarrhoea
Tremor of hands
Palpitations
Sore eyes, goitre
Tachycardia and arrhythmia 
High blood pressure

Endocrinology (9 decks)

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