L08 - Thyroid Disease: Hyper, Hypo and Other Flashcards
(34 cards)
what may be patients with a goitre??
Patients with a goitre may be:
— Hyperthyroid
— Euthyroid (normal thyroid function)
— Hypothyroid
how to examine the thyroid
Low down in neck
Feel for thyroid cartilage
(‘Adam’s apple’) then down & laterally
Moves on swallowing
Listen for a bruit
Retrosternal extension
— Can you get below it?
— Percuss over sternum
Check cervical LNS
What could cause tracheal deviation
retrosternal goitre
how to interpret thyroid function tests
how much of pop are checked
what thyroid antibodies
think about whats not working properly and what is driving the system
Checked in 1:4 population annually!
Thyroid autoantibodies
— Anti-TPO AB - Thyroid peroxidase auto-antibody
— TRAB - TSH receptor autoantibody
TSH
what is the shape of the curve of density
response to change
best biomarker of thyroid status
shape of curve - tails off from 3 upwards (incr in freq of thyroid autoantibodies)
slow to respond to change (
assumes normal pit function
remember -ve feeback reg
THYROID ANTIBODIES
how can you use these as a biomarker. how useful are they.
what are the different types of thyroid antibodies?
Prevalence of autoAB > autoimmune disease
— Marker of risk, or causal?
— Many autoAg are sequestered / intracellular
‘Negative’ autoAB result does not exclude
autoimmune disease; presence helps confirm
diagnosis
Different types of thyroid autoantibodies:
— “destructive” — target thyroid for autoimmune
destruction
“stimulatory” — stimulate TSH receptor
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 eg face puffy and pale Periorbital oedema Dry flaking skin Diffuse hair loss Bradycardia Signs of median nerve compression (carpal tunnel) Effusions, eg ascites, pericardial Delayed relaxation of reflexes Croaky voice Goitre Rarely stupor or coma Croaky voice Goitre
PRIMARY HYPOTHYROIDISM
causes
SECONDARY HYPOTHYROIDISM
causes
Autoimmune hypothyroidism
Hypothyroidism after treatment for hyperthyroidism (iatrogenic)
Thyroiditis
Drugs (e.g. lithium, amiodarone)
Congenital hypothyroidism
Iodine deficiency (not UK)
for 2ary
diseases of the hypothalamus or pituitary
what investigations are done for suspected hypothyroidism
bonus: what levels would you suspect for primary hypothyroidism
TSH and FT4
blood results confirm primary –> high TSH, low FT4
could check thyroid autoantibodies
no imaging necessary
what treatment for hypothyroidism
when would you alter the dosage
— Start with thyroxine (T4) 100 ug daily
Shorter symptomatic period
Unless elderly / ischaemic heart disease
— Start 25 pg daily with increments 4-6 weekly
— Usual dose 100-150 ug daily
‘ Some variation with body weight
— Aim normal FT4 without TSH suppression
‘ Individual variation: may need fine tuning within reference
ranges
— No evidence in properly conducted trials to support
T4/T3 combination therapy
What are the different types of AUTOIMMUNE HYPOTHYROIDISM?
Chronic autoimmune thyroiditis:
— Hashimoto’s disease
• With a goitre
‘ With a lymphocytic infiltration
Myxoedema (coma):
• Myxoedema = accumulation of glycosaminoglycans in
interstitial spaces of tissues
• Very severe hypothyroidism (any cause)
HYPERTHYROIDISM
aka?
Symptoms?
SIgns?
thyrotoxicosis
SYMP Weight loss Lack of energy Heat intolerance Anxiety/irritability Increased sweating Increased appetite Thirst Palpitations Pruritus Weight gain Loose bowels Oligomenorrhoea
SIGNS Tremor Warm, moist skin Tachycardia Brisk reflexes Eye signs Thyroid bruit Muscle weakness Atrial fibrillation
Thyroid eye disease TED / thyroid associated opthalmopathy TAO
what is it associated with
what increases the risk
what is it mediated by
where is the inflammation
what can be helpful to do
Associated with autoimmune hyperthyroidism (Graves disease) in 20% of patients — Graves and TED may not occur at the same time, or at all
Increased risk in smokers
Autoantibody mediated
Inflammation of all orbital
tissues except the eye
—Fat, muscles, conjunctiva, eyelids, extraocular muscles
Thyroid eye disease TED / thyroid associated opthalmopathy TAO
MILD and WORRISOME symptoms
MILD SYMP
‘itchy’ / dry eyes
• Artificial tears help
‘prominent’ eyes / change in
appearance
WORRISOME SYMP:
Diplopia / loss of sight — Loss of colour vision Grey / blurred patches — Redness / swelling of conjunctiva — Unable to close eyes fully — Ache / pain / tightness in or behind eye
Signs associated with thyrotoxicosis
Hands — Fine tremor — Warm Pulse — Sinus tachycardia — Atrial fibrillation Neck — Goitre — Move when swallow ---Smooth / not — Bruit/ not
Eyes
— Lid retraction / lid lag
— Proptosis / exophthalmos
Ophthalmoplegia
Abnormal eye movements
• Causes diplopia
— Inflammation (conjunctiva)
Thyrotoxicosis causes?
how does autoimmune one work also list some other causes
autoimmune hyperthyroidism (grave’s disease)
autoantibody stimulates TSH receptor which causes XS thyroid hormone and thyroid growth - goitre
Other: Toxic multinodular goitre Toxic adenoma Thyroiditis Drugs - eg amiodarone
Gestational Thyrotoxicosis
Placental ß-human chorionic gonadotrophin is
structurally similar to TSH and TSH-like action on the thyroid
More likely if hyperemesis / twin pregnancy
Settles after 1st trimester of pregnancy
What diagnostic features increase the likliness that the cause of hyperthyroidism is graves?
Helpful diagnostic features
(cause of hyperthyroidism)
Likely Graves disease:
— Personal or family history of any autoimmune
thyroid / endocrine disease
— Goitre with a bruit = Graves disease
— Thyroid eye disease = Graves disease (20%)
— Positive thyroid autoantibody titre
CASE
low TSH
FT4 FT3 high
what does this mean
INTERPRETATION? — Hyperthyroidism — 'Driven' by the thyroid ' Autonomous function of the thyroid • TSH-receptor autoantibodies (Graves disease) ' Remember the negative FB loop!
What further investigations can you do for suspected hyperthyroidism
Further investigations
‘ Thyroid autoantibodies
’ May not need any imaging
— clinical diagnosis may be clear
’ Thyroid uptake scan (isotope scan)
— Functional scan: darker areas of increased activity
Graves disease treatment options
Risks of no treatment
Medical
Radioiodine
Surgery
’ Symptom control
— ß-blockers (propranolol)
• Not if asthmatic
' Risks of no treatment — Symptoms worsening — Atrial fibrillation • Stroke — Osteoporosis • Fractures
Medical therapy for hyperthyroidism
— Carbimazole or propylthiouracil (PTU) — 18 months — 2 years — Titrate or block-replace — Rare side effect: agranulocytosis — Approx one third long term cure rate — Two thirds relapse • Usually first year • Cannot predict in advance
Radioiodine
what is the treatment like how does it work
when would you do it
what is the risk of perm hypo after
when wouldnt you do it
what is the aftercare like and what are the after effects
— Oral treatment, radioiodine concentrated in thyroid, radiation
kills thyroid cells
— Medical therapy first till euthyroid
— Approx 40% risk permanent hypothyroidism after treatment
— Not if pregnant / breast feeding
— Need to avoid prolonged close contact with others for 1-2
weeks after treatment
• Tricky if young children
— Not if severe thyroid eye disease
— Future pregnancies
• Women advised to wait 6m, men 4m
— Warn patients about airplane security systems!
