Hyperthyroidism Flashcards
What is hyperthyroidism?
pathologically increased thyroid hormone production + secretion by the thyroid gland
What is thyrotoxicosis?
Clinical manifestation of excess circulating thyroid hormones due to any cause
List 6 causes of thyrotoxicosis
Graves’ disease (most common)
Toxic multi nodular goitre
Acute phase of de Quervain’s thyroiditis
Acute phase of postpartum thyroiditis
Acute phase of Hashimoto’s thyroiditis
Amiodarone
What is primary hyperthyroidism?
Thyrotoxicosis caused by abnormality of the thyroid gland e.g. Graves’ disease or nodular goitre
What are the 2 subtypes of primary hyperthyroidism?
Overt: TSH < normal, T3/T4 > normal
Subclinical: TSH < normal, T3/T4 normal
List 4 risk factors for development of hyperthyroidism
F > M
FH
Smoking
Other AI disease e.g. T1DM
What is Graves’ disease?
AI disorder mediated by TSH receptor antibodies
TRAbs timulate TSH receptor, leading to thyroid hyperplasia + unregulated excessive production + secretion of thyroid hormone
List 3 signs specific to Graves’ and not seen in other causes of thyrotoxicosis
Eye signs (30%)
Pretibial myxoedema
Thyroid acropachy
What eye signs may be seen in Graves’ disease?
Exophthalmos
Ophthalmoplegia
Conjunctival oedema
Optic disc swelling
Inability to close eyelids may lead to sore, dry eyes (risks exposure Keratopathy)
What is thyroid acropachy?
Triad of:
Digital clubbing
Soft tissue swelling of hands + feet
Periosteal new bone formation
What is the most important modifiable risk factor for thyroid eye disease in Graves’ disease?
Smoking
How does radio iodine affect thyroid eye disease?
Increases inflammatory Sx of thyroid eye disease
Which antibodies may be found in Graves’ disease?
TSH receptor stimulating antibodies (90%)
Anti-thyroid peroxidase antibodies (75%)
Describe Thyroid Scintigraphy in Graves’ disease
Diffuse, homogenous, increased uptake of radioactive iodine
Describe initial management of Graves’ disease
Propanolol to block adrenergic effects (palpitations, tremor, tachycardia)
Refer
Specialists: ATD e.g. Carbimazole (if Sx not controlled by propranolol)
What are anti-thyroid drugs aka? Give 2 examples
Thionamides
Carbimazole
Propylthiouracil
Describe the titration regime of carbimazole for Graves’ disease
Start Carbimazole 40mg
Reduce gradually to maintain euthyroidism
Continued for ~12-18 months
What is the ‘block and replace’ regime of Carbimazole for Graves’ disease?
Start Carbimazole 40mg
Add Thyroxine when patient is euthyroid
Tx lasts ~6-9 months
Compare the regimes of carbimazole use in Graves’ disease
ATD titration regime suffer fewer side-effects than those on block-and-replace regime
What is the main adverse effect of carbimazole?
Agranulocytosis
What is the main risk of propylthiouracil?
Severe liver injury
When is propylthiouracil used first line in Graves’ disease?
Pre-pregnancy/ 1st Trimester
(Carbimazole a/w congenital abnormalities)
When is radio-iodine used in Graves’ disease?
Relapse following ATD therapy
Resistance to primary ATD Tx
What are the contraindications to radio-iodine for Graves’ disease?
Pregnancy (+ avoid for 4-6 months following Tx)
Age < 16y .
Relative CI: Thyroid eye disease- may worsen the condition
What proportion of patients receiving radio-iodine for Graves’ become hypothyroid?
Depends on dose
Majority require thyroxine supplementation after 5y
Describe management of thyroid eye disease
TOP lubricants: help prevent corneal inflammation caused by exposure
Steroids: Prednisolone
Orbita irradiation
Rehabilitative surgery
For patients with established thyroid eye disease, which 6 features indicate the need for urgent review by ophthalmology?
Unexplained deterioration in vision
Awareness of change in intensity or quality of colour vision in 1/ both eyes
Hx of eye suddenly ‘popping out’ (globe subluxation)
Obvious corneal opacity
Cornea still visible when eyelids are closed
Disc swelling
What is Toxic Multinodular Goitre?
Thyroid gland containing a number of autonomously functioning thyroid nodules resulting in hyperthyroidism (2nd most common cause)
Describe nuclear scintigraphy in Toxic multi nodular goitre
Patchy uptake.
Describe management of Toxic multinodular goitre
Radioiodine therapy
What is Thyrotoxicosis without hyperthyroidism?
Thyrotoxicosis without thyroid gland overactivity
Usually transient
List 3 causes of thyrotoxicosis without hyperthyroidism
Postpartum thyroiditis
Subacute (de Quervain’s) thyroiditis
Drug induced: Amiodarone induced thyrotoxicosis
List features of thyrotoxicosis by system
General: WL, ‘Manic’, restlessness, Heat intolerance
Cardiac: Palpitations, tachycardia
high-output HF (elderly), reversible cardiomyopathy (rare)
Skin: Sweating, Pretibial myxoedema,
Thyroid acropachy
GI: Increased appetite, Diarrhoea
Gynae: Oligomenorrhea, sub fertility
Neurological: Anxiety, Tremor
What is pretibial myxoedema?
Erythematous, oedematous lesions above the lateral malleoli
What is thyroid storm?
Rare but life-threatening complication of thyrotoxicosis.
Typically seen in those with established thyrotoxicosis, rarely seen as presenting feature
List 4 precipitating events of thyroid storm
Thyroid or non-thyroidal surgery
Trauma
Infection
Acute iodine load e.g. CT contrast media
List 7 clinical features of thyroid storm
Fever > 38.5ºC
Tachycardia
Confusion + agitation
N+V
HTN
Heart failure
Abnormal LFTs +/or jaundice
Describe management of thyroid storm
High dose Anti-thyroid drugs: Carbimazole or propylthiouracil
+
Hydrocortisone IV (reduce peripheral conversion of T4 to the more active T3)
+
B-blockers: IV propranolol
+
Lugol’s iodine
+
Symptomatic Tx e.g. paracetamol
Tx of underlying precipitating event
Why may colestyramine be considered in management of thyroid storm?
= bile acid-sequestering agent
Reduces enterohepatic circulation of thyroid hormones.