Endocrinology 7 - Thyroid disorders

Question 1

What is the origin of the thyroid?

Answer 1

Back of the tongue.

Question 2

What glads are embedded in the thyroid?

Answer 2

Parathyroid glands.

Question 3

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

Answer 3

The recurrent laryngeal nerve and it supplies the larynx (voice box) and allows speech.

Question 4

What are 3 problems that can occur with the development of the thyroid?

Answer 4

1. Agenesis - complete absence of thyroid.
2. Incomplete Descent - It may not descend to the correct point in the neck.
3. Thyroglossal cyst - cysts may form.

Question 5

Who is a Cretin (Felyx) ?

Answer 5

An individual with irreversible brain damage caused by lack of thyroxine. Main features - IQ much lower than normal and stunted growth.

Question 6

How do you prevent Cretinism?

Answer 6

1. Heel-prick test for all babies to test thyroid function (TSH levels). THIS IS DONE AFTER 5-10days as neonate will have mother’s thyroxine.
2. Thyroxine given immediately if TSH is found to be abnormally high.
3. Guthrie Test done as well for Phenylketonuria (brain damage).

Question 7

What are the roles of the thyroid gland? (2)

Answer 7

1. Synthesis, storage and secretion of thyroid hormones.

2. Thyroid hormones regulate growth, development and basal metabolic rate.

Question 8

What is the difference between thyroglobulin and thyroxine binding globulin?

Answer 8

Thyroglobulin is found in the colloid whereas thyroxine binding globulin is a specific plasma protein which binds to thyroxine in circulation.

Question 9

What is Primary Hypothyroidism (myxoedema)?

Answer 9

1. It is as a result of autoimmune response.
2. Thyroidectomy can also cause myxoedema.
3. TSH levels will rise in order to stimulate more thyroxine production but will eventually fall as it becomes exhausted.

Question 10

What is the effect of thyroxine on the pituitary and hypothalamus?

Answer 10

Thyroxine will have negative feedback on both the pituitary and hypothalamus. Hence will inhibit the production of TSH (pituitary) and TRH (hypothalamus).

Question 11

What are the main features of primary hypothyroidism? (7)

Answer 11

Everything slows down.

1. Deepening voice.
2. Depression and tiredness.
3. Cold intollerence.
4. Weight gain and reduced appetite.
5. Constipation.
6. Eventually myxoedema coma.
7. Bradycardia (slow heart rate)

Question 12

What is the treatment for hypothyroidism?

Answer 12

1. Giving thyroxine daily.

2. Monitor TSH and adjust dose of thyroxine until TSH level normal.

Question 13

What is hyperthyroidism?

Answer 13

It is when you produce too much thyroxine. TSH falls to zero. Can also be referred to as thyrotoxicosis.

Question 14

What are the main features of hyperthyroidism? (6)

Answer 14

Everything speeds up.

1. Feeling hot in all weather.
2. Increased appetite but weight loss.
3. Diarrhea.
4. Raised heart rate.
5. Raised basal metabolic rate.
6. Mood swings.
7. Myopathy (weak muscles).

Question 15

What are the causes of hyperthyroidism?

Answer 15

Grave’s disease - immune system produces an antibody that binds to TSHR in thyroid and hence thyroid becomes overactive. Other antibodies bind to muscles behind eye and pushes it forward (exophthalmos) and stimulate growth of soft tissues on shin and causes pretibial myxoedema.