Endocrinology 7 - Thyroid disorders Flashcards
What is the origin of the thyroid?
Back of the tongue.
What glads are embedded in the thyroid? And where in the thyroid are they?
Parathyroid glands. In the 4 corners of the thyroid.
What important nerve runs close to the thyroid gland and what does it supply? And how could thyroid surgery affect it?
- The recurrent laryngeal nerve and it supplies the larynx (voice box) and allows speech.
- Thyroid surgery could severe this nerve resulting in altered speech.
What are 3 problems that can occur with the development of the thyroid?
- Agenesis - complete absence of thyroid.
- Incomplete Descent - It may not descend to the correct point in the neck.
- Thyroglossal cyst - cysts may form.
Who is a Cretin (Felyx)? What are their main features?
- An individual with irreversible brain damage caused by lack of thyroxine.
- Main features - IQ much lower than normal and stunted growth.
How do you prevent Cretinism?
- 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.
- Thyroxine given immediately if TSH is found to be abnormally high.
- Guthrie Test done as well for Phenylketonuria (brain damage).
What are the roles of the thyroid gland? (2)
- Synthesis, storage and secretion of thyroid hormones.
2. Thyroid hormones regulate growth, development and basal metabolic rate.
What is the difference between thyroglobulin and thyroxine binding globulin?
Thyroglobulin is found in the colloid whereas thyroxine binding globulin is a specific plasma protein which binds to 75% of thyroxine in circulation.
What is Primary Hypothyroidism (myxoedema)?
- It is as a result of autoimmune response.
- Thyroidectomy can also cause myxoedema.
- Thyroxine levels decline = TSH levels will rise in order to stimulate more thyroxine production but will eventually fall as it becomes exhausted.
What is the effect of thyroxine on the pituitary and hypothalamus?
- Thyroxine will have negative feedback on both the pituitary and hypothalamus.
- Hence will inhibit the production of TSH (pituitary) and TRH (hypothalamus).
What are the main features of primary hypothyroidism? (9)
Everything slows down.
- Deepening voice.
- Depression and tiredness.
- Cold intollerence.
- Weight gain and reduced appetite.
- Constipation.
- Eventually myxoedema coma.
- Bradycardia (slow heart rate).
- Amenorrhoea.
- Heart enlargement - is not pumping properly.
What is the treatment for hypothyroidism?
- Giving thyroxine daily.
2. Monitor TSH and adjust dose of thyroxine until TSH level normal.
What is hyperthyroidism?
- It is when you produce too much thyroxine.
- TSH falls to zero.
- Can also be referred to as thyrotoxicosis.
What are the main features of hyperthyroidism? (9)
Everything speeds up.
- Feeling hot in all weather.
- Increased appetite but weight loss.
- Diarrhea.
- Raised heart rate.
- Raised basal metabolic rate.
- Mood swings.
- Myopathy (weak muscles).
- Palpitations.
- Tremor in hands.
What are the causes of hyperthyroidism?
- 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.
What is the foramen caecum?
Dimple at the back of the tongue (left by the disappearing thyroglossal duct).
What is the weight of an adult thyroid?
20g
Describe the embryological development of the thyroid gland
- Origin is the midline of the floor of the pharynx.
- Forms a duct which elongates down (thyroglossal duct).
- Migrates down into 2 lobes.
- Thyroglossal duct disappears.
- Thyroid gland then develops.
When will the thyroid reach its final position during development?
By week 7
What is a lingual thyroid? What problem does this cause?
- Where the thyroid tissue barely descends and remains very close to the back of the tongue.
- Causes problems with breathing.
What is thyroxine essential for?
Normal brain development.
Is thyroid disease more common in females or males? And what is the ratio?
- Much more common in females.
2. Ratio is 4:1
Can you measure TSH or TRH in the blood of someone who is missing thyroxine?
- TSH.
2. TRH will also be high but is undetectable in the blood.
What happens if you do not treat hypothyroidism?
- Death.
2. Rise in cholesterol - increased risk of death from heart attacks and strokes.
What is a goitre?
The enlargement of the thyroid.
What is the difference between myxoedema and pretibial myxoedema?
- Pretibial myxoedema is the swelling that occurs in shins of patients with Grave’s disease.
- Myxoedema is hypothyroidism.
