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Endocrinology > General thryoid disorders (7) > Flashcards

General thryoid disorders (7) Flashcards

1
Q

where is the thyroid located

A

It is located in the neck

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2
Q

What is the origin of the thyroid?

A

Back of the tongue

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3
Q

Where is the foramen caecum?

A

Dimple at the back of the tongue (left by the disappearing THYROGLOSSAL DUCT)

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4
Q

What is the adult thyroid weight?

A

20g

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5
Q

How many lobes are there? Which is the largest?

A

2

Right lobe is larger than the left

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6
Q

What glands are found embedded in the thyroid?

A

Parathyroid glands

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7
Q

What important nerve runs close to the thyroid gland and what does it supply?

A

recurrent laryngeal nerve. innervates the larynx (voice box) allowing speech

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8
Q

what would happen if the recurrent laryngeal nerve was damaged

A

Damage can cause changes in quality of voice, or even difficulty talking  Thus all thyroid surgeons mention this when obtaining consent for thyroidectomy.

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9
Q

where does the thyroid gland originate

A

base of the tongue where a midline outpouching forms of the floor of the pharynx

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10
Q

what is the thyroglossal duct

A

outpouching forms a ducht which elongates down.

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11
Q

what happens after the thyroglossal duct forms

A

it migrates down the neck and divides into 2 lobes

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12
Q

what is the foramen caecum

A

(at week 7) where the duct disappears leaving a dimple at the back of the tongue. the thyroid gland then develops.

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13
Q

what are the 3 problems that can occur with development of the thyroid

A

agenesis, incomplete descent and thyroglossal cyst

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14
Q

what is agenesis

A

complete absence of the thyroid

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15
Q

what is incomplete descent

A

it may not descend to the correct point in the neck. this may cause problems with delivery (i.e. base of tongue to trachea).

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16
Q

what is thyroglossal cyst

A

the thyroglossal duct may persist. cysts may form - presenting as a lump years later

17
Q

what is lingual thyroid

A

where the thyroid tissue barely descends at all and remains very close to the back of the tongue - this can cause problems with breathing. (complete failure to descend from base of tongue )

18
Q

what is thyroxine

A

Essential for normal brain development. Controls cellular activity

19
Q

what is a cretin

A

an individual with irreversible brain damage caused by lack of thyroxine

20
Q

what are the features of cretinism

A

lower IQ than normal. stunted growth.

21
Q

how is cretinism prevented

A

all babies at 5-10 days have a heel prick test to acquire blood to test thyroid function (measuring TSH). If TSH is high thyroxine is given immediately.
Guthrie Test for Phenylketonuria is also done. The test isn’t done immediately after birth because the neonate may have the mother’s thyroxine

22
Q

what is Thyroxine binding globulin

A

a specific plasma protein which binds 75% of thyroxine in the circulation

23
Q

what are the roles of the thyroid gland

A

Normally responsible for the synthesis, storage and secretion of thyroid hormones

24
Q

what is the role of thyroid hormones

A

regulate growth, development and basal metabolic rate

25
Q

What is the epidemiology of Thyroid Disease

A

Affects 5% of the population. Female:Male ratio = 4:1. Overactive and underactive thyroid occurs at equal frequency

26
Q

What is myxoedema - primary hypothyroidism

A

This is primary thyroid failure causes thyroxine levels to decline. Adenohypophysis detects this fall and secretes TSH. TSH level rise - to try and stimulate the production of more thyroxine. Eventually TSH levels will fall as it becomes exhausted

27
Q

What are the two causes of myxoedema - primary hypothyroidism

A

Autoimmune damage to the thyroid and Thyroidectomy which is an operation that removes or damages the thyroid gland

28
Q

What is the Hypothalamo-pituitary-thyroidal axis

A

The hypotalamus secretes TRH, which stimulates adenohypophysis to secrete TSH, which stimulates thyroxine release from thyroid. Thyroxine release has a direct negative feedback effect on the pituitary to inhibit TSH production. It also has an indirect negative feedback effect on the hypothalamus to inhibit TRH production. These negative feedback loops make sure that blood thyroxine concentration hardly changes

29
Q

Why is only TSH measured when thyroxine is missing.

A

if you’re missing thyroxine you will have high TSH and TRH. Only TSH is measured because TRH is pretty much undetectable in the blood

30
Q

What are the features of primary hypothyroidism (everything slows down)

A

Deepening voice. Depression and tiredness. Cold intolerance. Weight gain with reduced appetite. Constipation (bowels slow down). Bradycardia. Eventual myxoedema coma (brain stops functioning due to lack of thyroxine). Amenorrhoea may occur in late disease. Heart enlargement

31
Q

What is the treatment of hypothyroidism

A

If not treated, cholesterol increases causing death from MI/stroke. Treatment involves giving thyroxine daily. Monitor TSH and adjust dose of thyroxine until TSH is normal

32
Q

What is primary hyperthyroidism/thyrotoxicosis

A

Overactive thyroid gland makes too much thyroxine. TSH falls to zero - because there is no need to stimulate the production of thyroxine

33
Q

What are the clinical features of primary hyperthyroidism/thyrotoxicosis

A

Myopathy. Mood swings. Feeling hot in all weather. Diarrhoea. Increased appetite but weight loss. Tremor of hands. Sore eyes. Goitre (enlarged thyroid). Sleep difficulties. Palpitations

34
Q

What are the causes of primary hyperthyroidism/thyrotoxicosis

A

Graves’ disease triggers hyperthyroidism because the immune system produces an antibody which pretends to be TSH. The antibody binds to the TSH receptor and the thyroid gland becomes overactive. This can lead to goitre. Other antibodies bind to muscles behind the eye causing exophthalmos(swollen eye). Other antibodies stimulate the growth of soft tissue on the shin and causes pretibal myxoedema (hypertrophy).

35
Q

what are the features of primary hyperthyroidism/thyrotoxicosis (everything speeds up)

A

Increases BMR. Raised body temperature. Weight loss due to increased calorie burning. Tachycardia

36
Q

What is graves disease

A

Whole gland is smoothly enlarged and the whole gland is overactive

37
Q

What is pretibal myxoedema

A

Its the swelling (non-pitting) that occurs on the shins of patients with Graves’ disease. Caused by the growth of soft tissue. This is different to myxoedema/hypothyroidism

Endocrinology (12 decks)

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