13 Thyroid Disorders Flashcards
What is primary hypothyroidism?
thyroid function test results
Low levels of blood T4 due to a problem of thyroid gland itself (often autoimmune)
T3/T4 low
TSH high
What is secondary hypothyroidism?
thyroid function test results
Low levels of T4 due to TSH deficiency (pituitary disease)
.
low T4
non elevated TSH
What is subclinical hypothyroidism?
thyroid function test results
Normal fT4 with elevated TSH
Treatment of subclinical hypothyroidism
Treatment is not always needed if asymptomatic
if TSH >10miU/L then thyroxine should be prescribed
or TSH 5-10miU/L in women planning pregnancy
Causes of primary hypothyroidism
- autoimmunity e.g. hashimoto’s disease - most common
- iodine deficiency
- post surgery or radiation
- medication e.g. amiodarone, lithium
- dyshormonogensis - hereditary defects in thyroid hormone synthesis
- pregnancy
Causes of secondary hypothyroidism
TSH deficiency due to hypothalamic-pituitary disease
Symptoms of hypothyroidism
lethargy
Weight gain/change in appearance
Puffy eyes (myxoedema)
Cold intolerance
Dry hair/skin
Joint/muscle ache
Constipation
Signs of hypothyroidism
- Bradycardia
- Slow-relaxing reflexes
- Peaches and cream-smooth pale skin, pink cheeks
- loss of eyebrows
- Pre-orbital oedema
- Carpal tunnel syndrome
- cold hands
What does the sign of peaches and cream mean?
Smooth pale skin with pink cheeks
Investigations of hypothryoidism
- TFTs
- autoantibodies test (thyroid peroxide in Hasimoto’s disease)
Treatment of hypothyroidism
Thyroxine replacement therapy T4 for life
Caution needed in elderly and heart disease (lower dose needed)
Aims of treatment of hypothyroidism
what do the TSH levels indicate?
Resolution of symptoms
Normalisation of blood tests after 6-8 weeks
High TSH indicates under-replacement
Low TSH indicates over-replacement
What is primary hyperthyroidism/thyrotoxicosis?
thyroid function test results
High levels of thyroid hormones due to an overactive thyroid gland
T3/T4 high
TSH low
Causes of hyperthyroidism
- Graves’ disease - most common
- thyroiditis
- excessive T4/3 therapy
- drugs e.g. amiodarone
- thyroid carcinoma
- post-partum thyroiditis
- toxic multinodular goitre
- ectopic thyroid tissue
Symptoms of hyperthyroidism
- weight loss with increased appetite
- irritability
- restlessness/insomnia
- heat intolerance
- sweating
- muscle ache
- palpitations
- diarrhoea
- reduced fertility
Signs of hyperthyroidism
- resting tremor
- hyperkinesis - state of excessive restlessness
- resting tachycardia (sinus or atrial fibrillation)
- warm peripheries
- hypertension
- proximal myopathy- symmetrical weakness of limbs
- lid lag - upper eyelid is higher than normal when looking down
Proximal myopathy meaning
Symmetrical weakness in limbs
Lid lag meaning
What is it due to?
Upper eyelid is higher than normal when looking down
Increased sympathetic tone in upper eyelid
What is Graves’ disease?
- Autoimmune condition
- Immune system mistakenly attacks thyroid which cause it to be overactive > hyperthyroidism
- caused by production of thyroid stimulating immunoglobulin
Clinical signs specific to Graves’ disease
- thyroid eye disease - exophthalmos
- skin changes > pre tibia myxoedema
- thyroid acropathy (similar to clubbing)
What is nodular thyroid disease?
Solid or fluid filled lumps within thyroid
Investigations of hyperthyroidism
thyroid function test results
- TFTs
- autoimmune antibodies - TSH receptor stimulating antibodies (TSHrAb) for Graves’
- thyroid USS
- nuclear imaging - thyroid scintigraphy (to determine cause)
What is the imaging process to look at the thyroid gland?
Thyroid scintigraphy
Using technetium-99m isotope
What is seen on thyroid scintigraphy in the following conditions?
- Graves’ disease
- nodular disease
- thyroiditis
- thyroid cancer
- Graves’ disease: uniform increased uptake
- nodular disease: increased uptake in autonomonous nodules
- thyroiditis: absent uptake
- thyroid cancer: cold/absent area
Treatment of hyperthyroidism
- Medication - thionamides: carbimazole + propylthiouracil
- B blockers to control symptoms until thyroid function returns to normal
- thyroidectomy
- single dose of I131 radioactive iodine
What are the medications used to treat hyperthyroidism?
thionamides
Carbimazole
Propylthiouracil
How do thionamides work?
How long does it take?
What can be given in the meantime?
- reduces T3/T4 synthesis by preventing thyroid peroxidase from coupling + iodinating tyrosines
- 4-6 weeks
- B blockers to control symptoms
Side effects of thionamides
What should patients be warned of?
- rash
- bone marrow suppression
. - if they get an unexplained fever or sore throat, an urgent FBC is needed to exclude pancytopaenia
What must patients be advised to do after being administered radioactive iodine + why?
avoid children + pregnant women for a few week after treatnet
a small amount of radiation is emitted post treatment
Complications of thyroid surgery
- bleeding
- infection
- damage to recurrent laryngeal nerve
- damage to parathyroid gland > temporary or permanent hypocalcaemia
What is thyroid crisis/storm?
Large amount of thyroxine released in short amount of time
Rare complication of hyperthyroidism
Medical emergency - life threatening
Symptoms of thyroid crisis/storm
Hyperpyrexia >41.5°C
Tachycardia
Cardiac failure
Liver dysfunction
What can happen in pregnancy with hyperthyroidism?
In Graves’ disease antibodies can cross placenta
Baby can be born with hyperthyroidism
What is goitre?
Enlargement of thyroid gland
Types of goitre
- Diffuse goitre- simple goitre, autoimmune thyroid disease, thyroiditis
- Nodular goitre- multinodular goitre, solitary nodule RED FLAH SYMPTOM
- Fibrotic goitre- Riedel’s thyroiditis RARE
- Iodine deficiency- common worldwide, rare in UK
Red flag symptoms of thyroid cancer
Very young or old
Rapid enlargement of lump in neck
Hoarse voice + dysphagia -swallowing issues
Family history
Hard irregular thyroid mass
Fixed to surrounding structures
Cervical lymph nodes
Where does a thyroglossal cyst present?
Exact midline
Moves up when you stick tongue out
Investigation of suspected thyroid cancer
Thyroid ultra-sound
Fine needle aspiration
CT scan thorax and mediastinum - space within chest
What does hypothyroidism cause in infants + adults?
Infants - cretinism
Adults - myxoedema
what is severe hypothyroidism in infants + how does it present?
Cretinism
- dwarfed stature
- mental deficiency
- poor bone development
- slow pulse
- muscle weakness
What does TRH stand for?
Thryoptropin-releasing hormone
Thyroid function test in hashimoto’s disease
Low T3+4
High TSH
Thyroid function test in grave’s disease
- increased T3+4
- low TSH
What does a high T3/T4 with non suppressed TSH suggest?
TSHoma
thyroid hormone resistance
assay interference
What antibodies are related to thyroid disorders?
- anti-TPO - Grave’s disease+ Hashimoto’s thyroiditis
- anti-thyroglobulin - Grave’s disease, Hashimoto’s thyroiditis + thyroid cancer
- TSH receptor antibodies - Grave’s disease
