8. Thyroid disease: hyper, hypo and other Flashcards
What is hypothyroidism?
Underproduction of thyroid hormone
Difference between primary and secondary hypothyroidism?
primary - due to a thyroid problem
secondary - due to a hypothalamic/pituitary problem
hyperthyroidism/thyrotoxicosis
overproduction of thyroid hormone
euthyroid
normal production of thyroid hormone
goitre
enlargement of thyroid gland
Patients with a goitre may be:
hyperthyroid
euthyroid (normal thyroid function)
hypothyroid
How do you examine the thyroid?
Low down in neck, feel for thyroid cartilage (Adam’s apple), then down & laterally
moves on swallowing
listen for bruit
Retrosternal extension: can you get below it? percuss over sternum. Check cervical LNS
What to consider when interpreting thyroid function tests?
- remember the thyroid axis and negative feedback regulation
- what isn’t working properly?
- what is driving the system?
Normal ranges for thyroid hormones?
TSH 0.3-4.2 mu/l FT4 12-22 pmol/l FT3 3.1-6.8 pmol/l thyroid autoantibodies: -anti TPO AB - thyroid peroxidase auto-antibody -TRAB - TSH receptor autoantibody
TSH
best biomarker of thyroid status
Slow to respond to change - about 6 weeks
assumes normal pituitary function
remember negative feedback regulation
Thyroid autoantibodies
Prevalence of autoAB is much higher than autoimmune disease presence- marker of risk rather than causal
many autoAg are sequestered/intracellular
‘negative’ autoAB result doesn’t exclude autoimmune disease, but presence helps confirm diagnosis
different types of thyroid ABs:
-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
Symptoms 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
Causes of primary hypothyroidism
- Autoimmune hypothyroidism
- Hypothyroidism after treatment for hyperthyroidism (iatrogenic)
- Thyroiditis
- Drugs (e.g. lithium, amiodarone)
- Congenital hypothyroidism
- Iodine deficiency (not UK)
Causes of secondary hypothyroidism
Diseases of hypothalamus or the pituitary gland
Hypothyroidism investigations
Look at FT4 first to see if hypo or hyper then TSH to see if primary or secondary
Blood results to confirm primary/secondary hypothyroidism
Could check thyroid autoantibodies
No imaging necessary
Hypothyroidism treatment
Start with thyroxine (T4) -100 mg daily
-Shorter symptomatic period
-Unless elderly / ischaemic heart disease
-> Start 25 mg daily with increments 4-6 weekly
Usual dose 100-150 mg 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
Symptoms of hyperthyroidism
Weight loss Lack of energy Heat intolerance Anxiety/irritability Increased sweating Increased appetite Thirst Palpitations Pruritus Weight gain Loose bowels Oligomenorrhoea (scarce periods)
Signs of thyrotoxicosis
Tremor Warm, moist skin Tachycardia Brisk reflexes Eye signs Thyroid bruit Muscle weakness Atrial fibrillation
Symptoms of thyroid eye disease (TED)/ thyroid associated opthalmopathy (TAO)
- 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
- CT scan imaging helpful
Mild symptoms of thyroid eye disease
itchy’ / dry eyes -Artificial tears help
‘prominent’ eyes / change in appearance
worrisome symptoms of thyroid eye disease
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 -Bruit / not Eyes -Lid retraction / lid lag -Proptosis / exophthalmos -Ophthalmoplegia -Abnormal eye movements, Causes diplopia -Inflammation (conjunctiva)
Causes of thyrotoxicosis
Autoimmune (Graves) Toxic multinodular goitre toxin adenoma thyroiditis drugs e.g. amiodarone
Graves disease
Autoantibody stimulates the TSH receptor, causing excess thyroid hormone production and thyroid growth (goitre)
Accounts for 75% of cases
• Typically women 30-50 yrs
Gestational thyrotoxicosis
Placental β-human chorionic gonadotrophin is structurally similar to TSH and TSH-like action on the thyroid
likely if hyperemesis / twin pregnancy
Settles after 1st trimester of pregnancy
Helpful diagnostic features of Graves disease
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
Further investigations for Graves disease
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
• Medical • Radioiodine • Surgery • Symptom control ○ Beta-blockers (propranolol), not if asthmatic • Risk of no treatment ○ Symptoms worsening ○ Atrial fibrillation e.g. stroke ○ Osteoporosis e.g. 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 therapy
RADIOACTIVE IODINE TREATMENT (I-131)
• 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!
Surgery for thyrotoxicosis
• Sub-total thyroidectomy (“almost total”)
• Patients must be euthyroid pre-operatively
○ Medical therapy first
• Risks
○ Anaesthetic
○ Neck scar
○ Hypothyroidism
○ Hypoparathyroidism
○ Vocal cord palsy (recurrent laryngeal nerve damage)
Treatment for a toxic adenoma or toxic multinodular goitre
• Initial treatment: short term medical therapy (to control thyroid function tests)
Subsequent curative treatment: radioiodine
Agreeing expectations
Reassurance that variety of Sx all relate to hyperthyroidism
• E.g. swings in emotion, anxiety, panic, irritability
May take time to feel ‘normal’ again
• Even after TFTs normalise, may be ‘lag’ phase of few months due to ‘metabolic rollercoaster’
Treatments for thyroid do not help eye disease
Risk of weight gain – watch dietary intake!
Confirm ‘family’ plans / intentions – guide treatment
Thyroid eye disease treatment options
‘Active’
• Encourage smoking cessation
• Steroids
○ Pulsed IV methylpred / oral prednisolone
• Other immunosuppressive / steroid-sparing agents
• Radiotherapy
‘Burnt out’
• May be left with disfigurement causing impaired quality of life and social avoidance
• Surgical treatment
○ Orbital decompression
○ Eyelid surgery
Thyroid storm
Who gets it? • Usually 2º Graves • Unrecognised • Incompletely treated ○ “start-stop” ○ erratic compliance ○ early on in course of treatment ○ Surgery / radioiodine treatment without adequate preparation • RARE! What triggers it? • Surgery (GA) • Childbirth • Acute severe illness ○ Infection ○ Trauma ○ Diabetic ketoacidosis ○ Stroke ○ Pulmonary embolus
Features of a thyroid storm
• Multi-system • Graves ○ Goitre, thyroid eye disease • Hyperpyrexia • CNS ○ Agitation, delirium • Cardiovascular ○ Tachycardia >140 bpm ○ Atrial dysrhythmias ○ Ventricular dysfunction ○ Heart failure • GI ○ Nausea & vomiting ○ Diarrhoea ○ Hepatocellular dysfunction Degree of elevation of thyroid hormone concentrations does NOT distinguish uncomplicated thyrotoxicosis from thyroid storm High mortality rate ITU-level care
Thyroiditis
Usually self-limiting thyroid disease Transient mild thyrotoxicosis • Always resolves (1-2 m) • b-blockers if required • Isotope scan would be ‘cold’ • Anti-thyroid drugs will not work Longer hypothyroid phase (4-6 m) • 80% normal at 1 year • May require thyroxine treatment for a while Annual TFTs: 30% hypothyroid @ 1 yr, 50% @ 3 yr
When to consider thyroiditis?
Consider if:
Patient is pregnant / within 1 year post-partum
risk T1 diabetes, FHx thyroid disease, smoker
Patient has very tender thyroid
• May be raised inflammatory markers
Clinical thyroid status does not fit with lab results
• Rapidly changing thyroid function tests
No diagnostic features of Graves disease
Current / recent treatment with immunomodulatory medication
Associations with thyroid disease
Other autoimmune endocrine diseases • Type 1 diabetes • Pernicious anaemia • Coeliac disease • Premature ovarian failure • Addison’s disease Syndromes • Turner syndrome • Down's syndrome Medication for other diseases • Lithium ○ Inhibits thyroid hormone synthesis & secretion • Amiodorone Annual thyroid functioning test screening recommended
Goitre & thyroid nodules in euthyroid patients
Euthyroid Goitre • Common • More common in iodine-deficient areas • May be multinodular • Usually nothing to worry about Thyroid nodule • Thyroid nodule in euthyroid patient • Must exclude thyroid cancer - 5% • Ultrasound scan characteristics helpful • Fine needle aspiration biopsy for cytology
