Thyroid disease Flashcards
What proportion of the UK population has hypothyroidism?
2%
What is another name of hyperthyroidism?
thyrotoxicosis
What is the gender ratio of thyroid disease?
10:1 F:M
What is the hormone loop that the thyroid is involved in?
- hypothalamus secreted thyrotropin-releasing hormone (TRH) which stimulates the anterior pituitary
- Anterior pituitary gland secretes thyroid-stimulating hormone (TSH)
- TSH acts on the thyroid gland increasing production of thyroxine (T4) and tri-iodothyronine (T3)
What is the role of T4 and T3?
act on variety of tissues helping to regulate use of energy sources, protein systhesis, and controls the body’s sensitivity to other hormones
What are the 3 groups that hypothyroidism can be classified into?
- Primary hypothyroidism
- Secondary hypothyroidism
- Congenital hypothyroidism
What is primary hypothyroidism?
problem with the thyroid gland itself, e.g. autoimmune
What is secondary hypothyroidism?
disorder with the pituitary gland (e.g. pituitary apoplexy) or lesion compressing pituitary gland
What is congenital hypothyroidism?
problem with thyroid dysgenesis or thyroid dyshormonogenesis
What is the most common cause of hypothyroidism?
Hashimoto’s thyroiditis
What are 3 diseases that Hashimoto’s is associated with?
- Type 1 diabetes mellitus
- Addison’s
- Pernicious anaemia
What can Hashimoto’s thyroiditis cause transiently in the acute phase?
thyrotoxicosis (hyPERthyroidism)
What is the commonest cause of thyrotoxicosis (hyperthyroidism)?
Graves’ disease
What is a feature of thyrotoxicosis specific to Graves’ disease?
thyroid eye disease
What are 6 other causes of hypothyroidism, in addition to Hashimoto’s thyroiditis?
- Subacute thyroiditis (de Quervain’s)
- Riedel thyroiditis
- Postpartum thyroiditis
- Drugs - lithium, amiodarone
- Iodine deficiency
- After thyroidectomy or radioiodine treatment
What are 2 features of subacute (de Quervain’s) thyroiditis?
- painful goitre
- raised ESR
What is Riedel thyroiditis?
fibrous tissue replacing the normal thyroid parenchyma
causes a painless goitre
What are 3 drugs which can cause hypothyroidism?
- Lithium
- Amiodarone
- Anti-thyroid drugs e.g. carbimazole
What is the most common cause of hypothyroidism in the developing world?
iodine
In addition to Graves’ disease what are 5 other causes of thyrotoxicosis?
- Toxic multinodular goitre
- Drugs - amiodarone
- Acute phase of subacute (de Quervain’s) thyroiditis
- Acute phase of post-partum thyroiditis
- Acute phase of Hashimoto’s thyroiditis
What is toxic multinodular goitre?
autonomously functioning thyroid nodules that secrete excess thyroid hormones
What are 10 symptoms of hypothyroidism?
- Weight gain
- Lethargy
- Cold intolerance
- Dry, cold, eyllowish skin
- Non-pitting oedema (face, hands)
- Dry, coarse scalp hair, loss of lateral aspect of eyebrows
- Constipation
- Menorrhagia
- Decreased deep tendon reflexes
- Carpal tunnel syndrome
What are 11 symptoms of thyrotoxicosis?
- Weight loss
- Manis, restlessness
- Heat intolerance
- Palpitations, may even provoke arrhythmias e.g. AF
- Increased sweating
- Pretibial myoxedema (above lateral malleoli)
- Thyroid acropachy: clubbing
- Diarrhoea
- Oligomenorrhoea
- Anxiety
- Tremor
What is the principle investigation in thyroid disease?
thyroid function tests
primarily look at serum TSH and T4
Which type of thyroid hormone is rarely used in cases of thyroid disease?
T3 - only clinically useul in small number of cases
What is an easy way to remember how cases of hyper- and hypothyroidism present in terms of TFTs?
often opposite: T4 low, TSH high in hypothyroidism and vice versa in hyperthyroidism
Which thyroid hormone is most sensitive for monitoring patients with existing thyroid problems and for guiding treatment?
TSH
How will thyroid function tests present in thyrotoxicosis e.g. Graves’ disease?
Low TSH, high free T4
How will thyroid function tests present in primary hypothyroidism e.g. Hashimoto’s thyroiditis?
High TSH, low free T4
What will TFTs show in secondary hypothyroidism?
low TSH, low free T4
What will TFTs show in sick euthyroid syndrome?
Low TSH, low free T4
When does sick euthyroid commonly occur and what is the management?
common in hospital inpatients; changes reversible upon recovery frmo systemic illnes and no treatment is usually needed
What are do TFTs show in subclinical hypothyroidism?
High TSH, normal T4
What does subclinical hypothyroidism represent?
common finding, represents patients on the way to developing hypothyroidism but still have normal thyroxine levels
What do TFTs show in poor compliance with thyroxine?
TSH high, T4 normal
What causes the abnormal TFTs in poor thyroxine compliance?
if poorly compliant may only take thyroxine in days before routine blood test, so thyroxine levels normal but TSH lags and reflects longer term low thyroxine levels
What are the 3 main thyroid autoantibodies that can be tested for in thyroid disease?
- Anti-thyroid peroxidase (TPO) antibodies - Hashimoto’s thyroiditis
- TSH receptor antibodies - Graves’ disease
- Thyroglobulin antibodies
What thyroid condition are TSH receptor antibodies associaed with?
Graves’ disease (90-100% of cases)
What thyroid condition are anti-TPO antibodies associated with?
Hashimoto’s thyroiditis
In addition to TFTs what is another test sometimes performed in thyroid disease and what can it show?
nuclear scintigraphy: toxic multinodular goitre reveals patchy uptake
What is the treatment of hypothyroidism?
thyroxine given in form of levothyroxine
What are 3 things that patients with thyrotoxicosis may be treated with?
- Propranolol - thyrotoxic symptoms e.g. tremor
- Carbimazole
- Radioiodine treatment
How does carbimazole work to treat thyrotoxicosis?
blocks thyroid peroxidase from coupling and iodinating the tyrosine residues on thyroglobulin - reduces thyroid hormone production
What is an important adverse effet of carbimazole to be aware of?
agranulocytosis
What may be seen in TFTs when steroid therapy is being used?
low TSH, normal T4
What can cause secondary hypothyroidism?
pituitary failure
What are 3 conditions that can be associated with hypothyroidism (in addition to the autoimmune conditions)?
- Down’s syndrome
- Turner’s syndrome
- Coeliac disease
What is the commonest cause of hypothyroidism in children (juvenile hypothyroidism)?
autoimmune thyroiditis
What are 3 causes of hypothyroidism in children?
- Autoimmune thyroiditis
- Post total-body irradiation eg. treatment for acute lymphoblastic leukaemia
- Iodide deficiency
What is the danger of not treating congenital hypothyroidism in babies?
irreversible cognitive impairment
What are 5 features of congenital hypothyroidism?
- Prolonged neonatal jaundice
- Delayed mental and physical milestones
- Short stature
- Puffy face, macroglossia
- Hypotonia
What is the significant of subclinical hypothyroidism?
risk of progressing to overt hypothyroidism 2-5% (higher in men)
Whatt are 2 factors that increase the risk of subclinical hypothyroidism becoming overt hypothyroidism?
- Male
- Presence of thyroid autoantibodies