Thyroid disease: hyper, hypo and other Flashcards
Hypothyroidism
Underproduction of thyroid hormone
Primary- due to a thyroid problem
Secondary- due to a hypothalamic/ pituitary problem
Hyperthyroidism
Thyrotoxicosis
Overproduction of thyroid hormone
Euthyroid
Normal production o f thyroid homrone
Goitre
Enlargement of thyroid gland
Patients may be
- hyperthyroid
- euthyroid
- hypothyroid
Examining the thyroid
Low down in the neck
Feel for thyroid cartilage then down and laterally
Moves on swallowing
Listen for a bruit
Retrosternal extension
Normal range thyroid function tests
TSH: 0.3-4.2 mu/l
FT4: 12-22 pmol/l
FT3: 3.1-6.8 pmol/l
Thyroid antibodies
- anti-TOP AB (thyroid peroxidase auto antibody)
- TRAB (TSH receptor auto antibody)
TSH
The best biomarker of thyroid status
Slow to respond to change (about 6 weeks)
Assumes normal pituitary function
Remember the negative feedback regulation
Thyroid autoantibodies
Prevalence of autoAB > autoimmune disease
- marker of risk, or causal
Negative autoAB result does not exclude autoimmune disease; presence heps confirm diagnosis
Different types of thyroid autoantibodies
- destructive- target thyroid for autoimmune destruction
- stimulatory- stimulate TSH receptor
Symptoms of hypothyroidism
May be none
Lethargy
Mild weight gain
Cold intolerance
Constipation
Facial puffiness
Dry skin
Hair loss
Hoarseness
Heavy menstrual periods
Signs of serve hypothyroidism
Change in appearance e.g. face puffy and pale
Perioribital oedema
Dry flaking skin
Diffuse hair loss
Bradycardia
Sings of median nerve compression (carpal tunnel)
Effusions e.g. ascites, pericardial
Delayed relaxation of reflexes
Croaky voice
Goitre
Rarely stupor or coma
Causes of primary hypothyroidism
Autoimmune hypothyroidism
Hypothyroidism after treatment for hyperthyroidism
Thyroiditis
Drugs (e.g. lithium, amiodarone)
Congenital hypothyroidism
Iodine deficiency
Causes of secondary hypothyroidism
Diseases of the hypothalamus or pituitary
Treatment for hypothyroidism
Start with thyroxine (T4) 100ug daily
- shorter symptomatic period
- unless elderly/ ischaemic heart disease
Usual dose 100-150ug 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
Chronic autoimmune thyroiditis
Hasimoto’s disease
With a goitre
With a lymphocytic infiltration
Myxoedema (coma)
Accumulation of glycosaminoglycans in interstitial spaces of tissues
Very severe hypothyroidism
Symptoms of thyrotoxicosis
Weight loss
Lack of energy
Heat intolerance
Anxiety/ irritability
Increased sweating
Increased appetite
Thirst
Palpitations
Pruritus
Weight gain
Loose bowel
Oligomenorrhoea
Signs of thyrotoxicosis
Tremor
Warm, moist skin
Tachycardia
Brisk reflexes
Eye signs
Thyroid bruit
Muscle weakness
Atrial fibrillation
Mild symptoms of thyroid eye disease/ thyroid associated opthalmopathy
Itchy/ dry eyes
Prominent eyes/ change in appearance
Worrisome symptoms of TED/ TAO
Diplopia/ loss of sight
Loss of colour vision
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
- opthalmoplegia
- inflammation
Causes of thyrotoxicosis
Graves disease
Autoantibody stimulates the TSH receptor
Causes excess thyroid hormone production and thyroid growth
Other causes of thyrotoxicosis
Toxic multinodular goitre
Toxic adenoma
Thyroiditis
Drugs (e.g. amiodarone)
Gestational thyrotoxicosis
Placental B-human chorionic gonadotrophin is structurally similar to TSH and TSH like action on the thyroid
Increased likeliness if hyperemesis/ twin pregnancy
Settles after 1st trimester of pregnancy
Likely Graves disease if
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
Graves disease treatment options
Medical
Radioiodine
Surgery
Symptom control
- beta blockers
Risks of no treatment
- symptoms worsening
- atrial fibrillation
- osteoporosis
Medical therapy of Graves disease
Carbimazole of propylthiouracil
18 months - 2 years
Titrate or block replace
Rare side effect: agranulocytosis
Approx 1/3 long term cure rate
2/3 relapse
- usually first year
Radioiodine
Oral treatment, radioiodine concentrated in thyroid, radiation kills thyroid cells
Medical therapy first till euthyroid
Not if pregnant. breast feeding
Need to acoid prolonged close contact with other for 1-2 weeks after
Not if severe thyroid eye disease
Surgery
Sub-total thyroidectomy
Patients must be euthyroid pre-operatively
Risks
- anaesthetic
- neck scar
- hypothyroidism
- hypoparathyroidism
- coval cord palsy
Treatment for a toxic adenoma or toxic multinodular goitre
Initial treatment: short term medical therapy
Subsequent curative treatment: radioiodine
Thyroid eye disease treatment options
Active
- encourage smoking cessation
- steroid
- other immunosuppressive/ steroid sparing agents
- radiotherapy
Burn out
- may be left with disfigurement causing impaired quality of life
- surgical treatment (orbital decompression, eyelid surgery)
Thyroid storm
Thyrotoxic crisis
Who gets thyroid storm?
Usually secondary graves
Unrecognised
Incompletely treated
- start- stop
- erratic compliance
- early on in course of treatment
- surgery/ radioiodine treatment without adequate preparation
What triggers thyroid storm?
Surgery
Childbirth
Acute severe illness
- infection
- trauma
- diabetic ketoacidosis
- stroke
- pulmonary embolus
What are the features of thyroid storm?
Multi-system
Graves (goitre, TED)
Hyperpyrexia
CNS (agitation, delirium)
CV (tachycardia, atrial dysrhythmias, ventricular dysfunction, heart failure)
GI (nausea and vomiting, diarrhoea, hepatocellular dysfunction)
Thyroiditis
Transient mild thyrotoxicosis
- always resolves
- beta blockers if required
- isotope scan would be cold
- anti thyroid drugs will not work
Longer hypothyroid phase
- 80% normal at 1 year
- may require thyoxine treatments for a while
Consider thyroiditis if
Patient is pregnant/ within 1 year post partum
Patient has very tender thyroid
Clinical thyroid status does not fit with lab results
No diagnostic features of Graves disease
Current/ recent treatment with immunomodulatory medication
Associations of autoimmune thyroid disease with other autoimmune endocrine diseases
Type 1 diabetes
Pernicious anaemia
Coeliac disease
Premature ovarian failure
Addison’s disease
Association of autoimmune thyroid disease with syndromes
Turner syndrome
Down’s syndrome
Association of autoimmune thyroid disease with medication for other diseases
Lithium
- inhibits thyroid hormone synthesis and secretion
Amiodarone
Euthyroid goitre
Common
More common in iodine deficient areas
May be multinodular
Usually nothing to worry about
Thyroid nodule
Must exclude thyroid cancer
Ultrasound scan characteristics helpful
Fine needle aspiration biopsy for cytology
