Lecture 7 - Thyroid Disorders Flashcards
Draw a diagram of the thyroid
2 major lobes, L and R (largest) 4 parathyroid glands Isthmus in centre Pyramidal lobe in triangle
What is the origin of the thyroid?
Back of the tongue
Where is the foramen caecum?
Dimple at back of tongue (disappearing thyroglossal duct)
What is the adult thyroid weight?
20g
How many lobes are there?
4 lobes
Where can you find aberrant parathyroid glands?
Can be higher up on neck
What is the foramen caecum?
The entry to the persistent thyroglossal duct
How is the thyroid formed embryologically?
Midline outpouching of floor of pharynx This forms duct which elongates down (thyroglossal duct) Migrates down neck and divides into 2 lobes
When does thymus move into final position?
By week 7
What happens to the thyroglossal duct?
It disappears leaving the foramen caecum, where the thyroid gland then develops
What are the dimensions of each lobe?
4*2.5*2.5cm
Which nerve runs close to the thyroid?
Left recurrent laryngeal nerve
Why is it difficult to operate on the thyroid?
Damage to the nerve can cause changes in quality of voice/difficulty talking
What are the main problems with development?
Agenesis Incomplete descent Thyroglossal cyst
What is agenesis?
Complete absence of gland Not very good prognosis as no thyroxine released
What is a thyroglossal cyst?
Segment of thyroglossal duct persists and presents as lump years later
What is the prognosis of a lingual thyroid?
Can be lethal if not treated with thyroxine
What is a lingual thyroid?
An ectopic thyroid present at the top of the throat, which hasn’t descended at all - surgery as treatment option
Why is thyroxine essential for brain development?
Neonates with T4 deficiency in utero have irreversible brain damage - CRETIN
What is a cretin?
Individual with irreversible brain damage caused by lack of thyroxine Has thicker tissues Stunted growth
How do you diagnose and treat cretinism?
Heel prick test at 5-10 days (mother’s T4 can falsify test) - measures TSH or Phenylketonuria (Guthrie test) Thyroxine given immediately after - if TSH too high
Where is thyroxine synthesised?
Thyroid follicular cell
What does the colloid contain?
Thyroglobulin and stored thyroxine
What is the difference between thyroglobulin and thyroxine binding globulin?
TBG bonds 75% of T4 in circulation VS Thyroglobulin is inside thyroid gland only
Thyroid diseases affect which sex more?
Females in a 4:1 ratio - women more susceptible to auto-immune diseases
What are the thyroid’s common functions?
Synthesis, storage and secretion of thyroid hormones -> regulate growth, development and metabolic rate
Thyroid disease affects how much of the population?
5% - 1:1 ratio of over and underactive thyroids
What are the type of thyroidisms?
Primary hypOthyroidism (myxoedema) Overactive thyroid gland (hypothyroidism) Graves’ Disease
What is Myxoedema - symptom of primary hypothyroidism?
1ry thyroid failure
Autoimmune/operation damage to thyroid
Thyroxine levels DECREASE > TSH levels INCREASE
What are some features of primary hypothyroidism?
Deepening voice
Depression and tiredness
Cold intolerance
Weight gain with reduced appetite
Constipation
Bradycardia
Eventual myxoedema coma
What are some methods of treatment of primary hypothyroidism?
Essential - death otherwise: Cholesterol ^ causing death from heart attacks/stroke Replace thyroxine - monitor levels, ensuring TSH returns to normal
What is an overactive thyroid gland?
TOO MUCH thyroxine TSH levels FALL to ZERO a.k.a. HYPERTHYROIDISM/THYROTOXICOSIS
What are the symptoms of an overactive thyroid gland?
^ basal metabolic rate
^ temperature - hot
^ appetite, lose weight
Tachycardia
Myopathy
Mood swings
Diarrhoea
Tremor of hands
Palpitations
Sore eyes, goitre
What are the causes of an overactive thyroid gland?
GRAVES’ DISEASE
Toxic multinodular goitre
Thyroiditis
What is Graves’ disease?
Whole gland is smoothly enlarged and overactive
Autoimmune disease - Ab bind and stimulate TSH receptor
Causes Goitre and HERT
What are the symptoms of Graves’ disease?
Proptosis, Periorbital oedema, PRETIBIAL MYXOEDEMA, Exopthalmos, Clubbing, Amenorrhea, Tremor
What is pretibial myxoedema?
Swelling occurring on shins of Graves’ patients - growth of soft tissue
What are the thyroid levels signs of OTG?
^ T3 and 4 LESS TSH
What are the thyroid level signs of OTG?
LESS T3 and 4 ^ TSH
