Thyroid disorders Flashcards
Where is the thyroid gland located?
Between C5-T1
What are the two lobes of the thyroid connected by?
The isthmus
What important structures are located close to the thyroid gland and must be considered when operating on the thyroid gland?
- Recurrent laryngeal nerve
- Superior laryngeal nerve
- Parathyroid glands
- Trachea
- Common carotid artery
- Internal jugular vein
What is T3 also known as?
Triiodothyronine
What is T4 also known as?
Thyroxine
Which of T3 and T4 is more active and which is produced more?
T3 is more active but more of T4 is released
What is the thyroid gland made up of?
Lots of follicles consisting of follicular cells surrounding a protein-rich material called the colloid
What does synthesis of T3 and T4 begin with?
Circulating iodine being actively transported with Na+ ions across the basolateral membrane of the follicular cells
Once inside the follicular callow does iodide cause T3/4 synthesis?
- Oxidised to iodine
- Iodine bind to tyrosine on thyroglobulin molecules
- If tyrosine binds to one iodine = T1, If bind to two = T2
- Thyroid gland is stimulated and the T1 and T2 molecules are cleaved from tyrosine and join to either make T3 or T4
- Follicular cells engulf the T3 and T4 containing portions of the colloid via endocytosis
- TSH stimulates movement of Colliod into secretory cells
- Proteolysis results in T3 and T4 release
How much iodinated thyroglobulin is stored in follicles?
Enough to provide thyroid hormone for several weeks even in the absence of dietary iodine
What is graves disease?
- Cause of hyperthyroidism
- Autoimmune condition that results in excess secretion of thyroid hormones and hyperplasia of thyroid follicular cells
What is a toxic multinodular goitre?
- Cause by a lack of dietary iodine
- The anterior pituitary compensates by producing more TSH leading to thyroid hypertrophy and hyperplasia
What is de quervain’s thyroiditis?
- Transient hyperthyroidism which sometimes results from acute inflammation of the thyroid gland
What drug can induce hyperthyroidism?
Amiodarone - an anti-arrhythmic drug that can cause both hypo and hyperthyroidism
What risk factors are associated with hyperthyroidism?
- Female
- Genetic
- Autoimmune disease
- Smoking
- Stress
What three effects does graves disease have?
- Hyperthyroid effects
- Opthamological effects
- Dermatological
What are the general signs of hyperthyroidism?
- Hands - palmar erythema
- Diffuse goitre
- Lid lag and stare
- Hyperkinesis
- Warm
Proximal myopathy and muscle wasting
What are the symptoms of hyperthyroidism?
- Palpitations
- Diarrhoea
- Weight loss and increased appetite (due to higher metabolic rate)
- Oligomenorrhea +/- infertility
- Heat intolerance
- Irritability/behavioural change
- Anxiety
What would you see on a thyroid function test in hyperthyroidism?
TSH is low and T3 and T4 are raised
If there was a secondary cause of hyperthyroid what would be different about the TFTs?
TSH will be elevated as the problem is with the pituitary