Thyroid disorders

Question 1

What does the pyramidal lobe originate from?

Answer 1

back of tongue

Question 2

Where are the parathyroid glands located?

Answer 2

embedded at 4 corners of thyroid

control calcium

Question 3

What is the origin of the thyroid?

Where is the foramen caecum?

Answer 3

Origin: midline outpouching of floor of pharynx (base of tongue is origin)
Thyroid in final position by week 7

dimple at back of tongue
left by disappearing thyroglossal duct

Question 4

What is adult thyroid weight?

Answer 4

20g

4x2.5x2.5

Question 5

How many lobes are there? Which is bigger?

Answer 5

2, right larger

Question 6

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

Answer 6

recurrent laryngeal nere
innervates larynx allowing speech
can be severed in thyroid surgery and affect speech

Question 7

What are 3 common problems in thyroid development?

Answer 7

agenesis - complete absence of thyroid
incomplete descent - not to correct point, can cause delivery problems (if very close to back of tongue may affect breathing)
thyroglossal cyst - thyroglossal duct may persist, cysts may form

Question 8

What is essential for normal brain development?

Answer 8

thyroxine (T4)

Question 9

What is a cretin?

Answer 9

individual with irreversible brain damage caused by lack of thyroxine
lower IQ
stunted growth

Question 10

How to prevent cretinism?

Answer 10

heel prick test (test thyroid function measuring TSH)

• 5-10 days
• with Guthrie test for PKU
• not straight after birth as neonate may have mothers thyroxine
• if TSH/thyrotrophin very high, thyroxine given immediately

Question 11

Epidemiology of thyroid disease?

Answer 11

5% of population affected
more common in females (4:1 M/F ration)
overactive and underactive thyroid EQUAL FREQUENCY

Question 12

What is myoxedema?

Common cause?

Answer 12

primary hypothyroidism/ primary thyroid failure

autoimmune damage to thyroid/thyroidectomy
thyroxine levels decline, TSH increases to stimulate more thyroxine production but will eventually fall after exhaustion
high TRH

Question 13

Describe control cause of primary hypothyroidism?

Answer 13

lack of thyroxine
- no negative effect directly to pituitary to inhibit TSH production
- no indirect effect to hypothalamus to inhibit TRH production
NEGATIVE FEEDBACK LOOPS KEEP BLOOD THYROXINE [] CONSTANT

Question 14

Why measure TSH over TRH?

Answer 14

TRH almost undetectable in blood

Question 15

What are features of primary hypothyroidism?

Answer 15

EVERYTHING SLOWS
deeper voice
depression/tiredness
cold intolerance
weight gain, reduced appetite, constipation
bradycardia, hypertrophy as not pumping effectively
eventual myxoedema (brain stops function without thyroxine)
amenorrhea late in disease

Question 16

Treatment for hypothyroidism?

Answer 16

thyroxine daily
monitor TSH and adjust dose of thyroxine till TSH normal

if not, death
rise cholesterol increases risk of heart attack/stroke

Question 17

Describe the nature of hyperthyroidism?

Answer 17

too much thyroxine made = thyrotoxicosis, hyperthyroidism
TSH falls to zero (no need to stimulate thyroxine production)
raised BMR, temp, burn up calories and lose weight, increase HR

Question 18

Clinical features of hyperthyroidism?

Answer 18

myopathy
mood swings
hot all time
diarrhoea
increased appetite but weight loss
tremor of hands
palpitations
sore eyes, goitre (swelling of neck from enlarged lymph)

Question 19

What is a common cause of hyperthyroidism?

Answer 19

Graves’ disease - whole gland smoothly enlarged and overactive

• immune system produces antibody pretending to be TSH so Graves’ triggers hyperthyroidism
• antibody binds to TSH receptor and thyroid gland becomes overactive

Question 20

Clinical features of hyperthyroidism?

Answer 20

goitre - overactive and enlarged thyroid

exophthalmos/proptosis - antibodies bing to muscles behind eye and push it forwards

pretibial myxoedema - antibodies stimulate growth of soft tissue on shin and cause this hypertrophy
- non pitting swelling in Graves patients