Thyroid Disorders

Question 1

Describe where the thyroid gland is located and its anatomy?

Answer 1

-Thyroid gland is located at the back of the tongue.
Located in the neck and it is shield shaped.
It has a left lobe, right lobe and an isthmus in the middle.

Question 2

what is the pyramidal lobe?

Answer 2

It is part of the extension from the back of the tongue from which the thyroid originated.

Question 3

where are the parathyroid glands and what are they involved with?

Answer 3

Found embedded at the four corners of the thyroid, these parathyroid glans are involved in the control of calcium.

Question 4

What is the name of the dimple at the back of the tongue and what caused the formation of that structure?

Answer 4

Foramen Caecum

This is a remnant left by the descending thyroglossal duct.

Question 5

What is the weight and dimensions of a normal thyroid gland?

Answer 5

20 g

4 cm x 2.5 cm x 2.5 cm

Question 6

Which lobe of the thyroid is the biggest?

Answer 6

RIGHT > left

Question 7

What nerves run near the thyroid gland and what does it supply?

Answer 7

Recurrent laryngeal nerves.

-innervates the larynx (voice box) allowing speech.

Question 8

Describe the embryological development of the thyroid gland?

Answer 8

Origin: midline outpouching of the floor of the pharynx ( base of the tongue is the origin)
Outpouching forms a duct which elongates down- thyroglossal duct.
It migrates down the neck and divides into 2 lobes.
-usually the thyroglossal duct disappears leaving only a dimple at the back of the tongue called the foramen caecum.
The thyroid gland then develops.

Question 9

What are three problems that can occur with the development of the thyroid?

Answer 9

AGENESIS - complete absence of the thyroid
INCOMPLETE DESCENT - it my not descend to the correct point in the neck. This can cause problems with delivery.
THYROGLOSSAL CYST - thyroglossal duct persists and cysts may form years later.

Question 10

What is lingual thyroid?

Answer 10

Thyroid tissue barely descends at all and remains very close to the back of the tongue which can cause breathing difficulties.

Question 11

What is cretinism?

Answer 11

Irreversible brain damage caused by a lack of thyroxine

Question 12

State two features of cretinism.

Answer 12

Stunted growth

Low IQ

Question 13

How are newborns tested for cretinism and what is the treatment?

Answer 13

Heel-prick test

TSH is measured and if it is ABNORMALLY HIGH then they are given THYROXINE

Question 14

What other disease does the heel-prick test ?

Answer 14

The Guthrie Test for phenylketonuria.

Question 15

where is thyroxine synthesised and what is the role of the thyroid gland?

Answer 15

Thyroid follicular cell is the site of thyroxine synthesis. Thyroxine affects basal metabolic rate and every cell is controlled by thyroxine.

Role of the thyroid gland:

• responsible for the synthesis, storage and secretion of thyroid hormones.
• these hormones regulate growth, development and basal metabolic rate

Question 16

Is thyroid disease more common in males or females?

Answer 16

Females

Female: Male ratio = 4:1

Question 17

Define myxoedema.

Answer 17

Primary Hypothyroidism - primary thyroid failure

Question 18

What is the most common cause of primary thyroid failure?

Answer 18

Autoimmune damage to the thyroid

Question 19

How do TSH levels change in primary thyroid failure?

Answer 19

TSH levels rise to try and stimulate and increase in thyroxine production
(eventually the TSH production will become exhausted and it will decline)

Question 20

What exerts negative feedback on TSH and TRH release?

Answer 20

T3/T4 - direct negative feedback on the pituitary gland to inhibit more production of TSH and indirect negative feedback on the hypothalamus to inhibit production of TRH.

Question 21

State some features of primary hypothyroidism.

Answer 21

EVERYTHING SLOWS DOWN 
Deepening voice 
Depression and tiredness 
Bradycardia
Cold intolerance 
Weight gain and reduced appetite 
Constipation
Heart enlargement

Question 22

What is the treatment for hypothyroidism and what happens if left untreated?

Answer 22

Give THYROXINE daily and monitor TSH.

-death due to rise in cholestrol which increases risk of death from heart attacks and strokes.

Question 23

How does TSH change in hyperthyroidism/thyrotoxicosis?

Answer 23

TSH is low because the elevated Thyroxine exerts a powerful negative feedback effect on it
TSH falls to zero.

Question 24

State some features of hyperthyroidism and the clinical symptoms of this?

Answer 24

Raised metabolic rate 
Raised temperature
Lose weight + burn up calories 
Tachycardia
Clinical: diarrhoea, myopathy, mood swings, palpitations, feeling hot in all weather, goitre/sore eyes

Question 25

What is a common cause of hyperthyroidism?

Answer 25

Graves’ Disease

Question 26

What causes Graves’ disease?

Answer 26

The whole thyroid gland is SMOOTHLY ENLARGED and the whole gland is OVERACTIVE
Caused by the immune system producing an antibody that MIMICS TSH

Question 27

Other than an increase in thyroxine production, state 3 other features of hyperthyroidism.

Answer 27

GOITRE - enlargement of the thyroid could form a goitre
EXOPHTHALMOS - other antibodies could bind to the eye muscles pushing the eye forwards
PRETIBIAL MYXOEDEMA - other antibodies could promote growth of soft tissue on the SHIN