Endocrine 2 Flashcards
where is the thyroid gland located?
sits just below the larynx near the base of the neck
What are the 2 main hormones the thyroid gland produces, stores and secretes?
T4 ( thyroxine)
T3 (tri-iodothyronine)
Explain the thyroid negative feed back loop
- the hypothalamus detects a fall in T3 and T4
- the hypothalamus then releases TRH (thyrotropin releasing hormone)
- TRH stimulates the pituitary gland to release TSH (thyroid stimulating hormone)
- TSH acts on the thyroid gland to produce and release more T3 and T4 into the blood
- The hypothalamus will detect when there is adequate T3 and T4 in the blood stream and will stop secreting TRH
What is a primary endocrine disease?
there is a direct issue with the gland leading to over/under production of the hormone
what is a secondary endocrine disease?
there is an issue with the control mechanism of the gland (hypothalamus/pituitary) leading to over/under production of the hormone
what is thyrotoxicosis?
also known as hyperthyroidism
this is when the thyroid gland produces excess T3/T4 thyroid hormone
What are the primary causes of hyperthyroidism?
- graves disease
- toxic multi-nodular goitre/toxic adenoma
- viral thyroiditis
- drugs (amiodarone)
what drug can cause hyperthyoidism?
amiodarone - used to treat arrhythmia
what is the most common cause of hyperthyroidism?
Graves disease
What is graves disease?
an autoimmune disease
auto antibodies stimulate TSH receptors on the thyroid gland resulting in excess thyroid hormone (T3/T4)
also causes hyperplasia of the thyroid cells = goitre
What is a goitre?
A goitre is a lump or swelling at the front of the neck caused by a swollen thyroid.
What is the secondary cause of hyperthyroidism?
pituitary tumour - TSH secreting pituitary adenoma
What are the symptoms of hyperthyroidism?
- sweating
- heat intolerance
- irritability
- poor sleep
- anxiety
- heart palpitations
- increased appetite
- weight loss
- diarrhoea
- breathlessness
- irregular metabolism
What are the signs of hyperthyroidism?
- Exophthalmos (bulging eyeballs)
- tachycardia
- increased BP
- fine tremour
- goitre or nodule
- pre-tibial myxoedema (swelling and thick, scaly plaques in the lower legs)
what is pre-tibial myxoedema
swelling and thick, scaly plaques in the lower legs
what is exophthalmos?
Buldging eyes
caused by inflammation of the retro-orbital tissues causing proptosis, lid retraction and ophthalmoplegia (paralysis of eye muscles)
what would these clinical signs suggest:
- Exophthalmos (bulging eyeballs)
- tachycardia
- increased BP
- fine tremour
- goitre or nodule
- pre-tibial myxoedema (swelling and thick, scaly plaques in the lower legs)
Hyperthyroidism
what would these symptoms suggest:
- sweating
- heat intolerance
- irritability
- poor sleep
- anxiety
- heart palpitations
- increased appetite
- weight loss
- diarrhoea
- breathlessness
- irregular metabolism
hyperthyroidism
For primary hyperthyroidism:
What results would you expect to see from a thyroid function test?
- decreased TSH
- increased T3 and T4
For secondary hyperthyroidism:
What results would you expect to see from a thyroid function test?
- increased TSH
- increased T3 and T4
What blood test is used to diagnose hyperthryoidism?
Thyroid function tests
- increased T3 and T4
- low TSH (but in pituitary adenoma TSH may be normal or elevated)
TSH receptor antibodies (TRAb)
- positive in graves disease
What would you expect to see in a patient with graves disease blood tests?
- low TSH
- increased T3 and T4
- TRAb (TSH receptor antibodies) present
Apart from blood tests, what else can be used to diagnose hyperthyroidism?
Radiology
- thyroid USS
- thyroid radioisotope scan
Tissue
- US guided fine needle aspirate/biopsy
What drugs can be used to manage hyperthryoidism?
Anti-thyroid drugs
- Carbimazole, proylthiourcil
Beta blockers (control symtpoms of tachycardia and tremour while the other treatments work
