Hyperthyroidism Flashcards
What does TSH do?
Activates the uptake o iodine by the thyroid gland
Stimulates the production of thyroxine
How much Thyroxine do you store at once?
Enough for a whole month
So you can release it when it is required
How can thyroxine enter the blood stream from the thyroid gland?
Proteolytic enzyme forms a whole allowing thyroxine to enter the blood stream
What makes TRH?
Hypothalamus
What effects do T3 and T4 have on the pituitary and hypothalamus?
Negative
What level of TSH will you find in a patient wit primary hypothyroidism?
High TSH
Pituitary hormone tries to stimulate the production of Thyroxine since levels are low
How do we treat primary hypothyroidism?
Replacement by tablet
Increase does until TSH is normal
Will have to take for life
Once daily
What is the half-life of thyroxine?
10 days
Why is the half-life of thyroxine significant?
You can make up for missing a dose by taking a double dose
What is Graves’ disease?
Autoimmune
Antibodies bind to and stimulate the TSH receptor in the thyroid
Causes goitre (smooth) and hyperthyroidism
Give some symptoms of Graves
Perspiration Facial flushing Muscle wasting Shortness of breath Breast enlargement Expophthalmos Goitre Palpitaiton Increase appetite Tremor Localised myxoedema Oligomenorrhea/Amenorrhea
Why do you get exophthalmos?
Antibodies bind to growth factor receptor antibodies on muscles
at the back of the eye
What is pretibial myxoedema?
Swelling on the shins of patients with graves disease: growth of soft tissue
What is myxoedema?
Auto-immune hypothyroidism
What is an iodine uptake scan?
Give radioactive iodine
Goes into thyroid
Can show thyroid size and uniform radio iodine uptake
Very black
What is Plummer’s disease?
Toxic nodular goitre
Not immune
Benign adenoma that is overactive at making thyroxine
How do you differentiate between Graves’ and Plummer’s?
No exophthalmos
NO pretibial myxoedema
Different iodine uptake scans (one side and more at salivary glands)
What happens in Plummer’s disease?
Thyroid atrophies and shrinks away
Tumor is overactive
What can Plummer’s disease be known as?
Toxic nodular goitre
Single hot nodule
What are the effects of thyroxine on the sympathetic nervous system?
Sensitises beta adrenoreceptors to ambient levels of adrenaline and nor adrenaline
‘a bit of adrenaline goes a long way’
What does the adrenaline cause?
The minute they try to be active they get tachycardia, palpitation, tremor in hands and lid lag
What is lid lag?
Ask the patient to follow your finger
Eyelids are held back by adrenaline
What did the patient present with?
Weight loss despite increase appetite breathlessness Palpitations Tachycardia Sweating Heat intolerance Diarrhoea Lid lag and other sympathetic features
What is a thyroid storm?
Medical emergency: 50% mortality untreated
Blood results confirm hyperthyroidism
What are symptoms of a thyroid storm?
Hyperpyrexia > 41 Accelerated tachycardia / arrhythmia cardiac failure delirium / frank pschosis haptocellular dysfunction ; jaundice
What are treatment options for those with hyperthyroidism?
Surgery (thyroidectomy)
Radioiodine
Drugs
What classes of drugs are used to treat hyperthyroidism?
- The thionamides (thiourylenes; anti-thyroid drugs)
- propylthiouracil (PTU)
- carbimazole (CBZ) - Potassium Iodide
- Radioiodine
- β-blockers
What is the mechanism of action of thionamide?
Inhibits TPO
Blocks synthesis of T3/T4
Due to stores they don’t get better for a month
Why do you give the patient a beta-blocker with thionamide treatment?
Make them feel better whilst waiting for the thionamide to work
What are the side effects of thionamide treatment?
Agranulocytosis (usually reduction in neutrophils) - rare and reversible on withdrawal of drug.
rashes (relatively common)
What is the role of beta blockers in treating hyperthyroidism?
Several weeks for ATDs to have clinical effects e.g reduced tremor, slower heart rate, less anxiety
NON-selective (ie b1 & b2) b blocker
eg propranolol
achieves these effects in the interim
When do you give potassium iodide?
preparation of hyperthyroid patients for surgery
severe thyrotoxic crisis (thyroid storm)
What are the problems with thyroid surgery?
Risk of voice change
Risk of also losing parathyroid glands
Scar
Anaesthetic
How do you give radioiodine?
Swallow a capsule containing about 370 MBq (10 mCi) of the isotope I (131)
Contraindicated in pregnancy
Need to avoid children and pregnant mums for a few days
For scans only (not treatment), 99-Tc pertechnetate is an option.
Why must you isolate if you are taking radioiodine?
You emit radiation for 20 days
Must stay away from anyone who could be pregnant
Summarise the treatment options?
Drugs:
Beta blockade is VERY IMPORTANT
propranolol
Anti thyroid drugs :
Carbimazole
Propylthiouracil
Surgery
Radioiodide
What is viral thyroiditis?
Painful dysphagia
Hyperthyroidism
Pyrexia
Thyroid gland is visibly enlarged
What happened in viral thyroiditis?
Stop iodine uptake and the thyroid makes more virus instead
NO uptake of iodine
All stored thyroxine released
Present with typical features of hyperthyroidism
4 weeks later when the stored thyroxine is exhausted you become hypothyroid
Summaries the features of Viral (de Quervains) thyroiditis
Neck becomes painful All stored thyroxine released Free T4 levels rise TSH levels drop 1 month hyperthyroidism But NO new thyroxine is being synthesised
Patient becomes hypothyroid – gland stops making thyroxine and just replicates virus
Hypothyroidism lasts a second month
After 3 months, there is slow recovery
What is postpartum thyroiditis?
Similar to viral
but no pain only occurs after pregnancy
Immune system modulated during pregnancy
