Thyroid Disorders Flashcards
Label the parts of the Thyroid
What are the parathyroid glands?
Functionally unrelated - control calcium production
Located at the corners of the right and left lobes
Which lobe is larger, and how much does the thyroid weigh?
Right lobe larger than left.
~20g in adults
Where does the thyroid originate embryologically, and how does it develop?
Back of the tongue
Midline outpouching of floor of pharynx forms a thyroglossal duct which elongates downwards, allowing to migrate down the neck and divide into two loves; disappears to leave foramen caecum as thyroid gland develops in final position by week 7
What is the Foramen Caecum?
A dimple at the back of the tongue originating from the disappearance of the thyroglossal duct
What are the four possible problems with thyroid development?
- Agenesis: never develops at all
- Incomplete descent: does not descend fully from base of tongue to trachea
- Thyroglossal cyst: segment of duct persist and presents as a lump years later
- Lingual thyroid: no descent at all, remaining close to back of tongue and growing - need lifetime replacement of hormones if removed
What is a cretin?
Baby without thyroid gland, as no thyroxine is produced resulting in lower IQ and stunted growth.
How is cretinism detected?
Heel-prick test will show high TSH
Why does cretinism occur in utero?
Mothers thyroxine crosses placenta
(also why thyroxine isn’t tested for in heel-prick test, as will still be present)
What is Myxoedema?
Primary Hypothyroidism
What causes myxoedema/primary hypothyroidism?
Autoimmune damage causes gland to fail
Thyroidectomy
What can be detected in the blood during primary hypothyroidism?
Low thyroxine
High TSH - Until APG exhausted
(TRH also high, but cannot be detected in the blood)
What are the symptoms of Myxoedema?
Sx:
- Deepening voice (cartilage vibrations slow down)
- Depression, tiredness, cold intolerance, constipation, bradycardia
- Eventual coma (BMR so low that become unconscious)
- Cardiomegaly
What is the treatment for Myxoedema?
Tx:
- Thyroxine given daily
- Dose adjusted until TSH normal
- Needed otherwise death
- Excess cholesterol increases risk of death from MIs and Strokes
What is Thyrotoxicosis?
Hyperthyroidism
What would be detected in the blood during thyrotoxicosis?
High Thyroxine
No TSH, as no need to stimulate production of thyroxine
What are the symptoms of Thyrotoxicosis?
Sx:
- Myopathy
- Mood swings
- Diarrhoea
- Increased appetite
- Feeling hot
- Tremor
- Palpitations
- Sore eyes
What is a cause of Hyperthyroidism?
Graves’ Disease
What is Graves’ Disease?
Enlargement and overactivity of Thyroid gland
What causes Graves’ Disease?
Immune system produces antibody similar to TSH.
Antibody binds to TSH receptor, stimulating gland which becomes overactive and enlarges (goitre)
What are the other symptoms of Graves’ Disease?
- Goitre
- Pretibial Myxoedema (non-pitting swelling caused by growth of soft tissue on shins)
- Exophthalmos (proptosis) (pushing forewards of the eyes)
