Hypothyroidism

Question 1

Cause of primary hypothyroidism (myxoedema)

Answer 1

Autoimmune damage to the thyroid
post thyroidectomy
post radioactive iodine

Question 2

Thyroid function test in hypothyroidism

Answer 2

Low T3/T4
High TSH (thyroid stimulating hormone from the pituitary)

Question 3

Clinical features of primary hypothyroidism

Answer 3

Bradycardia
Voice deepens
Tired
Cold
Weight gain (BMR falls)
Decreased appetite 
Constipation

Question 4

How T3 is made and percentage from where….

Answer 4

Made by deiodination of T4 (by deiodinase)
80% from deiodination of T4
20% by direct thyroid secretion

Question 5

treatment for primary hypothyroidism

Answer 5

Thyroid hormone replacement therapy
Give T4 - **levothyroxine sodium; thyroxine sodium; thyroxine
Give T3 - liothyronine sodium

Question 6

Use of levothyroxine sodium (T4)

what levels are used as a guide

Answer 6

Used for primary hypothyroidism (autoimmune)
Oral once a day. TSH levels used as a guide
Also for primary hypothyroidism (iatrogenic)

Used for secondary hypothyroidism. No TSH is produced since problem is with the pituitary, so the middle of the reference range for free T4 is used.

Question 7

Use of Liothyronine sodium (T3)

Answer 7

for myxoedema coma (rare complication)
given IV (faster than T4)
then switch to oral

Question 8

Use of combination therapy (T3+4)

but may complain of symptoms…because

Answer 8

for patients that don’t feel better with T4 even if their TSH is normal

Palpitations
tremor
Anxiety

Because T3 is very potent (hard to get dose right) and switches off TSH

Question 9

adverse effects of thyroid hormone overreplacemnt

Answer 9

Symptoms of thyrotoxicosis. Low TSH

Skeletal - low bone density, osteoporosis, increased bone turnover

Cardiac - tacharrhythmia, dysrhthmia (atrial fibrillatoin)

Metabolism - increased energy expenditure, weight loss

Increased Beta-adrenergic sensitivity - tremor, nervousness