Endo - Hyperthyroidism Flashcards
What 2 ways does TSH cause and increase in thyroid hormone
Stimulates thyroxine production
Stimulates proteolytic enzymes to eat away colloid and release bound thyroxin into circulation
What regulates thyroid production
Negative feedback of T3 and T4 on the pituitary and the hypothalamus
What happens in primary hypothyroidism?
Immune system makes anti-thyroid antibodies therefore reduces the thyroid gland output
What happens in Grave’s disease?
Autoimmune condition whereby antibodies bind to TSH receptors and cause hyperthyroidism
What are the symptoms of Grave’s disease
Sweating Flushing Palpable lymph nodes Muscle wasting Shortness of breath Breast enlargement/ gynaecomastia Weight loss Heat intolerance Tachycardia Pretibial myxoedema Smooth diffuse goitre Tremor Irritability Increased appetite Exophthalmos Insomnia Diarrhoea
What causes exophthalmos
Separate autoantibodies bind to the muscles behind the eye
What causes an increase in heart rate and palpitations?
Increased thyroid hormone to increase sensitivity to adrenaline
What causes an increase in body temperature?
Increase in BMR
What causes pretibial myxoedema
Third antibody binds to the front of the tibia
How do we treat pretibial myxoedema
Topical steroids/ local injection to reduce inflammation
What does myxoedema usually refer to
Primary hypothyroidism
What is pretibial myxoedema?
Non pitting swelling that occurs in the tibial soft tissue of Grave’s disease patients
Describe the goitre seen in Grave’s
Smooth diffuse goitre that is uniform on both sides
How do we visualise the goitre in Grave’s
Radioactive iodine
What is Plummer’s disease?
Toxic nodular goitres which secrete T4
Is Plummer’s autoimmune?
No
As a result of Plummer’s not being autoimmune, what do we not see compared to Grave’s?
We don’t see exophthalmos or pretibial myxoedema
Why does Plummer’s give us an uneven appearance of thyroid gland?
Because the normal thyroid gland shrinks as only the nodular hot thyroid secretes hormones
What can we do to treat Plummer’s?
Hot nodule can be physically removed or we can give radioiodine
What are the effects of thyroxine?
Sensitises beta adrenoreceptors to ambient levels of adrenaline and noradrenaline
Apparent sympathetic activation
Tachycardia
Palpitations
Tremors in hands
Lid lag
What is thyroid storm?
Medical emergency arising form untreated hyperthyroidism
Why is thyroid storm an emergency?
50% mortality if left untreated - but is completely treatable
What are the signs of thyroid storm?
Hyperpyrexia (>41) Tachycardia (170+)/ arrhythmia Cardiac failure Delirium/psychosis Hepatocellular dysfunction; jaundice
How do we treat thyroid storm?
Thyroidectomy - can change voice
Radioiodine -radioactive for 6 days
Drugs
What are the 4 types of drugs we can use to treat hyperthyroidism?
Thionamides
Potassium iodide
Radioiodine
Beta blockers
What is the purpose of thionamides, potassium iodide and radioiodine
Daily treatment to reduce thyroid hormone synthesis
What is the purpose of beta blockers
Help with symptoms whilst treatment is waiting to kick in
What are the 2 thionamides we can use
Propylthiouracil (PTU)
Carbimazole (CBZ)
How do thionamides work?
Inhibit TPO therefore block T3/4 synthesis and secretion
What is the biochemical effect of thionamides?
Hours
What is the clinical effect of thionamides?
Weeks
What can we give whilst waiting for thionamides to work
Beta blocker e.g. propranolol
What are the side effects of thionamides
Agranulocytosis (neutrophils down) (rare)
Rashes (common)
When should we aim to stop thionamide treatment?
18 months. -regular review needed
What is the dose of KI we give with extreme hyperthyroidism
60mg x 3 daily
When is KI usually given
Preparation for surgery
How does KI work?
Wolk-Chaikoff effect
When do we start KI relative to an operation?
10 days before the operation to reduce blood flow to the thyroid gland during the surgery
What is in radioiodine capsules?
370 MBq (10mCi) of Iodine 131
When do we not give radioiodine?
Pregnancy or children
If we only want to use iodine for scanning, not treatment - what do we use?
99-Tc pertechnetate
What happens in viral (de Quervain’s) thyroiditis?
Virus takes over thyroid cells therefore they don’t make thyroid hormone, but there is destruction of cells so all thyroxin release to cause hyperthyroidism
What are the symptoms of de Quervains
Dysphagia
Painful neck
Pyrexia
Hyperthyroidism
What happens after a month of hyperthyroidism?
De Quervains
No more thyroxine and no more production therefore we get hypothyroidism for another month
How long does it take to recover from De Quervains
3 months
What happens in postpartum thyroiditis?
Similar to de Quervains but there is no pain and it happens after pregnancy - immune system modulated during pregnancy
