Thyrotoxicosis

Question 1

def

Answer 1

syndrome resulting from excess circulating free thyroxine(T4) and/or free tri-iodothyronine(T3)
due to either increased thyroid hormone synthesis (hyperthyroidism) or increased thyroid hormone release from an inflamed thyroid (thyroiditis)

Question 2

subclinical hyperthyroidism - thyroid hormone levels

Answer 2

normal T3/T4

low TSH

Question 3

aetiology

Answer 3

graves disease
toxic multinodular goitre
toxic adenoma
thyroiditis (post-partum or de quervains - post-viral)
drugs (amiodarone, self-adminstered T4)

Question 4

how does graves disease cause thyrotoxicosis

Answer 4

plasma IgG to thyroid TSH receptor stimulates thyroid hyperplasia and thyroid hormone hypersecretion

Question 5

epi

Answer 5

1% of females
0.1% of males
graves disease is the most common cause of hyperthyroidism overall
toxic multinodular goitre is the most common cause of hyperthyroidism in the elderly

Question 6

history

Answer 6

heat intolerance, sweating, palpitations, anxiety
weight loss despite good appetite, diarrhoea
exertional dyspnoea
decreased libido
menstrual irregularities in females
impotence in males

Question 7

history in graves

Answer 7

exophthalmos

double or blurred vision

Question 8

history in de quervains thyroiditis

Answer 8

flu-like illness

tender goitre

Question 9

examination

Answer 9

1 general
-underweight
-sweating
-restless
2 hands
-tremor
-warm & moist
-palmar erythema
3 BP
-WPP
4 Eyes
-lid retraction & lid lag
5 thyroid
-goitre
6 neurological
-proximal muscle weakness
-hyper-reflexia

Question 10

what causes lid lag and lid retraction in hyperthyroidism

Answer 10

increased catacholamine sensitivity of levator palpebrae superioris

Question 11

examination of hyperthyroidism with graves disease

Answer 11

thyroid acropachy (clubbing)
graves opthalmology
-exophthalmos
-double or blurred vision
pretibial myxoedema

Question 12

examination of thyroid crisis

Answer 12

hyperpyrexia
signs of dehydration
tachycardia
restlessness
coma

Question 13

investigations

Answer 13

1 TFTs
primary
-high T4/T3
-low TSH
secondary
-high T4/T3
-high or inappropriately normal TSH
2 radioisotope uptake scane
-graves disease has diffuse increased uptake
-toxic multinodular goitre has multiple areas of increased radio-isotope uptake (hot nodules) with suppression of uptake in other areas of the gland
-de quervains has no uptake
3 TSH receptor stimulating antibodies - positive in graves
4 CT/MRI of orbits for graves opthalmology

Question 14

what is used for a radioisotope uptake scan

Answer 14

99 technetium pertechnetate

Question 15

management in acute thyroid crisis

Answer 15

propylthiouracil
propanolol
IV hydrocortisone which inhibits peripheral conversion of T4 to T3
potassium iodide/Lugol's iodine
rehydrate and control temperature

treat underlying cause

Question 16

management for primary hyperthyroidism

Answer 16

1 medical
-anti-thyroid drugs (carbimazole, propylthiouracil, beta-blockers)
2 radioactive iodine
-must avoid pregnancy, pregnant women, young children
3 surgery
-for large goitres causing upper airway obstruction or dysphagia, and cannot take ATDs, and are pregnant or have moderate/severe graves opthalmology

Question 17

how do carbimazole and propylthiouracil treat hyperthyroidism

Answer 17

inhibit thyroid peroxidase and hormone synthesis

Question 18

complications

Answer 18

thyrotoxic crisis
HF
osteoporosis
infertilty

Question 19

complications with chronic subclinical hyperthyroidism

Answer 19

increased long-term risk of atrial fibrillation and decreased bone density

Question 20

prognosis

Answer 20

many patients become hypothyroid due to medication etc.