1b Hyperthyroidism Flashcards
Where is the thyroxine stored?
In the thyroid follicle which contains thyroglobulin
Describe the HPT axis
- Hypothlamus releases TRH
- This acts on the thyrotrophs in the pituitary to release TSH
- They act on thyroid to release T3 and T4
- These hormones then work by negative feedback to inhibit the pituitary and the hypothalamus at each level
What level of TSH will you find a patient with primary hypothyroidism, where the thyroid gland has been destroyed by the immune system?
`high TSH
How do you control thyroid replacement medications?
Give thyroxine medication
Increase the dose until the TSH falls to normal
Describe the typical appears of the thyroid gland in Graves disease
Smooth, diffuse, symmetrical enlargement of the thyroid gland, pain free when swallowing
What is Graves’ Disease?
An autoimmune condition in which antibodies bind to and stimulate the TSH receptor in the thyroid causing a smooth goitre and hyperthyroidism
What are the common symptoms of Grave’s Disease?
Pretibital Myxoedema
Exothphalmos
Weight loss
Tremor
Palpitations
Rapid pulse
Agitation
Smooth Goitre
What causes exophthalmos of the eye?
The antibodies bind to the muscles behind the eye and cause it to pop out the socket
What causes pretibial myxoedema?
When other antibodies bind to the muscles in he shin and cause hypertrophy of the skin - non pitting swelling
What is the investigation for Graves’ disease?
TSH-receptor antibody (Trab) measured in the bloodstream, positive in Graves’ disease
Diffuse goitre of moderate size and uniform radioiodine uptake
What is toxic nodular goitre disese?
A benign adenoma which is overactive and making too much thyroxine
Single/multiple toxic nodule
What is seen in patients with toxic nodular goitre disease?
Asymmetrical enlargement of the thyroid, with a single hot nodule seen on a radioiodine scan
What is the effect of thyroxine on the sympathetic nervous system?
Thyroxine sensitizes the beta adrenoreeptors to the ambient levels of adrenaline, so there is sympathetic activation
What symptoms are seen in hyperthyroidism due to the sympathetic activation?
Tachycadia, palpitations, tremor, weight loss despite increased appetite, breathlessness, heat intolerance, diarrhoea and lid lag
What causes lid lag?
This is inability of the eyelid to close properly due to the excess adrenaline which is holding the eyelid open
What are the features of a thyroid storm?
Fever (>41 degrees)
Accelerated tachycadia/arrhythmia
Cardiac Failure
delirium/ frank Psychosis
Liver failure , jaundice
What are the three options of treatment for hyperthyroidism/
Drugs
Radioiodine
Surgery
What are the three drugs used to control T4 levels in hyperthyroidism?
Thionamides (anti-thyroid drugs) - propylthiouracil PTU and carbimazole CBZ
Potassium Iodide
Radioiodine
beta-blockers
The first three reduce thyroid hormone synthesis and the last helps with symptoms
What drugs are used for symptomatic control in hyperthyroidism?
NOn-specific Beta blockers to reduce heart rate, tremors
How do thionamides work?
They inhibit thyroperoxidase synthesis therefore thyroxine cannot be made
What is a good non specific beta blocker which is used?
Propranolol
What are the unwanted actions of thionamides?
agranulocytosis and rashes
What is agranulocytosis?
a reduction in neutrophils - patients asked if they have a sore throat as the susceptibility to adaptive infections is higher
what is the role of beta blockers in thyrotoxicosis?
It takes several weeks for ATDs to have clinical effects \due to the stored thyroxine in the follicle for up to a month), therefore beta blockers work in the interim
