Hyperthyroidism

Question 1

what is it?

Answer 1

symptoms and signs occur as a result of excess T3 and T4

Question 2

definition of thyrotoxicosis

Answer 2

the clinical, physiological and biochemical state arising when the tissues are exposed to excess thyroid hormone

Question 3

definition of hyperthyroidism

Answer 3

refers specifically to conditions in which overactivity of the thyroid gland leads to thyrotoxicosis

Question 4

what is the difference between primary and secondary hyperthyroidism?

Answer 4

primary - indicated by high free T3/T4 and low TSH

secondary - high free T3/T4 and high TSH (or normal)

Question 5

what causes it?

Answer 5

thyroiditis 
ectopic production (struma ovarii)
factitious (exogenous intake)
excessive thyroid stimulation 
Grave's disease - 85% are due to Grave's disease 
Thyroid nodules with autonomous function 
- toxic solitary nodule 
- toxic multinodular goitre

Question 6

how can Grave’s disease cause hyperthyroidism?

Answer 6

Hashitoxicosis
thyrotropinoma (THSoma - very rare)
thyroid cancer - very rarely cause thyrotoxicosis
Choriocarcinoma (trophoblast tumour secreting hCG)

Question 7

how does it present (thyrotoxicosis)?

Answer 7

Increased  BMR
Very fast pulse rate 
Increased nervousness and excessively emotional
insomnia
Sweating & heat intolerance
Tendency to lose weight easily
Cardiac
o	Palpitation, atrial fibrillation (AF)
o	Cardiac failure (very rare)
Sympathetic
o	Tremor 
o	Sweating
CNS
o	Anxiety, nervousness, irritability, sleep disturbance
GI
o	Frequent, loose bowel movements
Vision
o	Lid retraction (not specific to Graves’)
o	Double vision (diplopia)
o	Proptosis (Graves’)
Hair and skin
o	Hair change – brittle, thin hair
o	Rapid fingernail growth
Reproductive
o	Menstrual cycle changes, including lighter bleeding and less frequent periods
Muscles
o	Muscle weakness, especially in the thighs and upper arms
Metabolism
o	Weight loss despite increased appetite
Thermogenesis
o	Intolerance to heat

Question 8

how is hyperthyroidism treated?

Answer 8

anti-thyroid drugs (ATDs)
B-blocker
Radioiodine
thyroidectomy

Question 9

anti-thyroid drugs

Answer 9

inhibit the TPO (thyroid peroxidase) thereby blocking hormone synthesis
Carbimazole - 1st line
Propylthiouracil (PTU) - 1st line in 1st trimester of pregnancy
Generally well tolerated however some get allergy symptoms and PTU can have a bad effect on the liver
o Highest risk in the first 6 weeks so warn patient verbally and in writing to stop drug and get urgent FBC checked in effect of fever, oral ulcer or oropharyngeal infection

Question 10

B-blockers

Answer 10

B-adrenoreceptor blockade, reduced activity of sympathetic nervous system
Propranolol – drug of choice, additional benefit of inhibition of DIO1
Need caution in asthma – risk of provoking bronchospasm, CCB can be used instead
Useful for immediate symptomatic relief of thyrotoxic symptoms

Question 11

Radioiodine

Answer 11

1st choice treatment for relapsed Graves’ disease and nodular thyroid disease
Contraindicated in pregnancy
Relatively contraindicated in active thyroid eye disease (can be used with steroid cover)
Contact precautions depending on dose given
High risk of hypothyroidism when used in Graves’ disease
No increased risk of thyroid cancer

Question 12

Thyroidectomy

Answer 12

useful when radioiodine is contraindicated 
scar and surgical/anaestheic risks 
recurrent laryngeal nerve palsy 
Hypothyroidism 
Hypoparathyroidism