Hyperthyroidism Flashcards
What is hyperthyroidism?
Over-production of thyroid hormone by the thyroid gland.
What is thyrotoxicosis?
Excessive quantity of thyroid hormone in circulation.
What is primary hyperthyroidism?
Thyroid itself produces excessive thyroid hormone.
What is secondary hyperthyroidism?
Excessive stimulation of the thyroid by the hypothalamus or pituitary.
What stimulates thyroid hormone synthesis?
TSH
Outline thyroid hormone synthesis.
- Tyrosine have 1 or 2 Iodides (iodination)
- Two tyrosines bind on the surface of a thyroglobulin (coupling)
- T3 and T4 made
Which thyroid hormone is mostly produced? What happens in circulation?
T4
Converted to T3
Which thyroid hormone is most metabolically active?
T3
Which enzyme powers thyroid hormone synthesis?
Thyroid peroxidase
What are thyroid follicles?
Thyroid follicle cells arranged into spheres, with a colloid centre
What is the most common cause of hyperthyroidism?
Grave’s
What is Grave’s disease?
Autoimmune- TSH Receptor antibodies, mimicking TSH to stimulate the thyroid.
What type of hyperthyroidism is Grave’s?
Primary hyperthyroidism
What is toxic multi-nodular goitre?
Nodules develop on the thyroid gland, acting independently to the feedback system.
What is toxic multinodular goitre also called?
Plummer’s Disease
What is exophthalmos?
Bulging of the eyes caused by Grave’s
Describe how exophthalmos occurs.
Inflammation behind the eye, with swelling of the tissue pushing the eyes forward.
What is pretibial myxoedema?
Mucin deposits under the skin of the anterior leg
What does pretibial myxoedema look like?
Waxy, oedematous skin, discoloured
What causes pre-tibial myxoedema and why?
Grave’s- reaction to TSH receptor antibodies.
What are the generic symptoms of hyperthyroidism?
- Irritable/Anxious
- Weight Loss
- Heat intolerance/Sweating
- Fatigue
- Tachy
- Loose stools
- Sexual dysfunction
What are the added symptoms in Grave’s?
Goitre
Exophthalmos
Pretibial myxoedema
What are the added symptoms in toxic multinodular goitre?
Goitre with nodules
What is a solitary toxic thyroid nodule?
Hyperthyroidism caused by one single nodule, usually a benign adenoma
What is De Quervain’s Thyroiditis?
How is it treated?
Viral infection causes hyperthyroidism, then hypothyroidism
NSAIDs for analgesia and beta blockers for symptom relief
How does De Quervain’s Thyroiditis present?
- Viral infection
- Fever
- Neck pain
- Dysphagia
- Hyperthyroid features
Why does De Quervain’s Thyroiditis eventually cause hypothyroidism?
Negative feedback
What is thyroid storm?
Hyperthyroidism with pyrexia and delirium
What is the first line treatment of hyperthyroidism?
Carbimazole
How does carbimazole work?
Decreases iodine uptake to the thyroid
How quickly does carbimazole work?
4-8 weeks
What options are there after carbimazole is successful?
- Titrated to maintain normal thyroid hormone levels
2. Completely inhibit thyroid production and treat with levothyroxine
When is carbimazole stopped?
Usually within 18 months
What is the second line drug in hyperthyroidism?
Propylthiouracil
Why isn’t propylthiouracil commonly used in hyperthyroidism?
Risk of severe hepatic reactions and death
How does radioactive iodine work in hyperthyroidism?
Taken up by the thyroid where the radiation destroys thyroid follicle cells
What can occur after radioactive iodine treatment and how is this treated?
Hypothyroidism- treat with levothyroxine
What are the rules of radioactive iodine use?
- Must not become pregnant within 6 months
- Must avoid contact with children and pregnant women for 3 weeks
- Must limit any social contact for several days after receiving a dose
Why are beta blockers used in hyperthyroidism?
- Thyroid hormones promote adrenaline release
- Beta blockers blocks adrenergic activity
- Symptoms controlled
Which beta-blocker is used in hyperthyroidism and why?
Propanolol
It’s non-selective unlike others, which only work on the heart
How is surgery used?
- Either the thyroid entirely or just nodules can be removed
- Treat with lifelong levothyroxine afterwards
What are the complications of hyperthyroidism?
- Exopthalmos/Pre-tibial myxoedema
- Hypothyroidism from treatment
- Miscarriage and Pre-eclampsia
- Tachy-Arrythmias
