Thyroid disorders Flashcards
(20 cards)
How can we classify thyroid disorders?
Based on symptoms
Based on causes
Why is classification of thyroid disorders based on symptoms not useful?
Tells us nothing about the mechanism of the disease
Solely whether it is hyperthyroidism or hypothyroidism
What are possible causes of thyroid disorders?
Iodide deficiency
Autoimmunity
Neoplasia - thyroid cancer/ nodule formation
What is the most common cause of thyroid disorders?
Iodide deficienct
Affects 2.7% of the population
Easily treated - add dietary salt or supplementation
Most common in underdeveloped areas
What is the consequence of iodide deficiency?
Enlarged thyroid gland -> goitre
What gland regulates TH synthesis?
Pituitary
What hormone regulates TH synthesis?
TSH
What happens when TH are larger than required?
Negative feedback loop
TH send negative feedback to the hypothalamus pituitary axis to decrease TSH release
What happens to TH synthesis in iodide deficiency?
Low T3 and T4 means negative feedback loop is compromised
Has long-term and short-term effects
- Short-term effect: TSH release T3 and T4 from gland stores
- Long-term effects: TSH enhances proliferation of thyroid cells = enlargement of thyroid gland and formation of goitre
What is the compensatory mechanism for formation of a goitre?
Ensures the gland absorbs all iodine from the circulation
What is a multinodular goitre?
Over time the large thyroid can develop nodules
What two autoimmune diseases affect the thyroid?
Grave’s disease
Thyroiditis
How do Thyroiditis and Grave’s differ?
Thyroiditis = autoantigens formed against the thyroid - leads to destruction and inflammation of the gland. Decreased TH levels
Grave’s = autoantigens are complementary for TSH receptors on gland. Increased TH levels.
Pathogenesis of thyroiditis
Destruction of thyroid gland by inflammatory cells
Antibodies against thyroid gland taget the cells
Infiltration of inflammatory cells - neutrophils and macrophages
Secretion of inflammatory mediators - induce damage to the thyroid cells
Inflammation and destruction of thyroid gland
What does Thyroiditis cause?
Hypothyroidism
Pathogenesis of Grave’s disease
Formation of autoantibodies targeted against TSH receptor
Agonist to TSH and causes release og T3 and T4
What does Grave’s cause?
Hyperthyroidism
What are symptoms of Grave’s?
Exophthalmos
Fat tissue in the eyes express TSH receptors
Proliferation of the cells in the orbit upon activation
Treatment of Hypothyroidism
Thyroxine structure is simple - easy to synthesise synthetically
Injection of supplements
Treatment of Hyperthyroidism
More complicated
- Inhibition of TH synthesis by inhibition of TPO
- Ablation - if the patient doesn’t respond to pharmacological inhibition
- Surgical or radioactive iodine
