8. Thyroid Disease Flashcards
hypothyroidism
underproduction of thyroid hormone
primary = due to thyroid problem
secondary = due to hypothalamic/pituitary problem
hyperthyroidism
thyrotoxicosis
overproduction of thyroid hormone
euthyroid
normal production of thyroid hormone
goitre
enlargement of thyroid gland
patient would be hyper, hypo or euthyroid
how to examine thyroid
low down in neck, feel for thyroid cartilage - down and laterally moves on swallowing listen to bruit (increased blood flow) retrosternal extension check cervical lymph nodes
thyroid function tests
TSH, FT4, FT3
thyroid antibodies - anti-TPO (thyroid peroxidase), TRAB-TSH receptor
TSH
best biomarker of thyroid status
slow to respond to change
assumes normal pituitary function
negative feedback regulation
thyroid autoantibodies
different types: destructive or stimulatory
marker of risk for autoimmune condition
hypothyroidism symptoms
may be none lethargy mild weight gain cold intolerance constipation facial puffiness dry skin hair loss hoarseness heavy menstrual periods
signs of severe hypothyroidism
change in appearance (face puffy and pale) preorbital oedema dry, flaky skin diffuse hair loss bradycardia carpal tunnel (median nerve compression effusions croaky voice goitre delayed relaxation of reflexes
causes of primary hypothyroidism
autoimmune hypothyroidism hypothyroidism after treatment for hyperthyroidism (iatrogenic) thyroiditis drugs congenital hypothyroidism iodine deficiency
causes of secondary hypothyroidism
rare
diseases of hypothalamus or pituitary
hypothyroidism investigations
blood tests to confirm - TSH high, FT4 low
could check thyroid antibodies
no imaging necessary
hypothyroidism treatment
daily thyroxine
aim = normal FT4 without TSH suppression
autoimmune hypothyroidism
chronic autoimmune thyroiditis - hashimoto’s
myxoedema (coma)
myxoedema
accumulation of glycosaminoglycans in interstitial spaces of tissues
occurs in very severe hypothyroidism
coma
thyrotoxicosis symptoms
weight loss lack of energy heat intolerance anxiety/irritability increased sweating increased appetite thirst palpitations pruritus weight gain loose bowels oligomenorrhora
signs of severe thyrotoxicosis
tremor warm, moist skin tachycardia brush reflexes eye signs thyroid bruit muscle weakness atrial fibrillation
thyroid eye disease (TED) and thyroid associated opthalmopathy (TAO)
associated with Grave's in ~20% increased risk in smokers antibody mediated inflammation of all orbital tissues except eye (fat, muscles, conjunctiva, eyelids) CT scan imaging helpful
TED/TAO mild symptoms
itchy/dry eyes
prominent eyes, change in appearance
TED/TAO worrisome symptoms
diplopia/loss of sight loss of colour vision redness/swelling of conjunctiva unable to fully close eyes ache/pain/tightness in or behind eye
signs associated with thyrotoxicosis - hands
fine tremor
warm, moist
signs associated with thyrotoxicosis - pulse
sinus tachycardia
atrial fibirillation
signs associated with thyrotoxicosis - neck
goitre
move when swallow
smooth/not
bruit/not
signs associated with thyrotoxicosis - eyes
lid retraction/lag
proptosis/exopthalmos
opthalmoplegia (abnormal eye movements, causes diplopia)
inflammation (of conjunctiva)
causes of thyrotoxicosis
autoimmune hyperthyroidism (Grave's) toxic multi nodular goitre toxic adenoma thyroiditis drugs (eg amiodarone) gestational
Grave’s disease
autoantibody stimulates TSH receptor
causes excess thyroid hormone production and thyroid growth (goitre)
accounts for 70% cases
gestational thyroiditis
placental beta-hCG is structurally similar to TSH - has similar action on thyroid
more likely if hyperemesis/twins
settles after 1st trimester
Grave’s - helpful diagnostic features
personal or family history of any autoimmune endocrine disease
goitre with bruit
thyroid eye disease
positive thyroid antibody titre
hypothyroidism investigations
low TSH, high FT3 and FT4
thyroid antibodies
may not need imaging
thyroid uptake scan (isotype test)
Grave’s treatment options
medical
radioiodine
surgery
risks of untreated Grave’s
symptoms worsen
atrial fibrillation
osteoporosis
Grave’s - medical treatment
carbimazole of propylthiouracil 18 months-2 years rare side effect = agranulocytosis ~1/3 cure rate 2/3 relapse: usually in first year
Grave’s - radioiodine treatment
oral - radioiodine concentrates in thyroid, radiation kills thyroid cells
medical treatment used until euthyroid
~40% risk fo hypothyroidism after
must avoid close treatment for 1-2 weeks after
not if severe thyroid eye disease
Grave’s - surgery
subtotal thyroidectomy (almost total)
patients must be euthyroid post-op
medical therapy first
risks: anaesthetic, neck scar, hypothyroidism, hypoparathyroidism, vocal cord palsy
toxic adenoma/multinodular goitre treatment
initially: short term medical therapy
subsequent curative treatment: radioiodine
thyroid eye disease treatment
encourage smoking cessation
steroids/other immunosuppressives
radiotherapy
surgical treatment: orbital decompression, eyelid surgery
thyroid storm
thyrotoxic crisis
rare, usually occurring in 2nd degree Grave’s
incomplete treatment - erratic compliance, start-stop, early in treatment
high mortality rate, ITU level care
features of thyroid storm
multi-system Grave's hyperpyrexia CNS - agitation, delirium CV - tachycardia, ventricular dysfunction, heart failure GI - nausea, vomiting, diarrhoea
thyroiditis
usually self-limiting
inflammation of thyroid
transient mild: always resolves 1-2 months
longer hypothyroid phase: 4-6 months, 80% after 1 year
autoimmune endocrine diseases associated with thyroid disease
type 1 diabetes pernicious diabetes coeliac anaemia coeliac disease premature ovarian failure Addison's disease
syndromes associated with thyroid disease
Turner syndrome
Down’s syndrome
euthyroid goitre
common
more common in iodine deficient areas
may be multi-nodular
usually nothing to worry about
thyroid nodule
must exclude cancer (~5%)
ultrasound characteristics helpful
fine-needle aspiration biopsy for cytology
