Hyper/hypothyroidism Flashcards
Types of hypo/hyperthyroidism?
Primary (majority) - problem is intrinsic within the thyroid:
• Non-goitrous
• Goitrous
• Self-limiting
Secondary (rare) - problem is at the level of the pituitary gland OR hypothalamus, e.g: a pituitary tumour that produces excessive TSH (causing hyperthyroidism) OR pituitary gland failure (causing hypothyroidism)
What is the commonest cause of thyroid disease?
Autoimmune disease
Thyroid hormones that can be measured?
TSH
T4 (free) and T3 (free)
Results in primary hypothyroidism?
TSH - high
T4/T3 - low
Results in primary hyperthyroidism?
TSH - low
T4/T3 - high
Results in secondary hypothyroidism?
TSH - low
T4/T3 - low
Results in secondary hyperthyroidism?
TSH - high
T4/T3 - high
Lab results of the different types of hypothyroidism?
ADD TABLE
What is hypothyroidism?
Variety of abnormalities cause insufficient secretion of thyroid hormones
What is myxoedema?
Either refers to:
• Myxoedema coma - severe hypothyroidism
• Pre-tibial myxoedema - accumulation of hydrophilic mucopolysaccharides in the ground substance of the dermis and other tissues (IT OCCURS IN HYPERTHYROIDISM)
Appearance of pre-tibial myxoedema?
Doughy induration of the skin classically seen in the shins
When does pre-tibial myxoedema occur?
Grave’s disease
Occurrence of hypothyroidism?
More common in women and subclinical hypothyroidism is more common than overt
Incidence is higher in Whites and in areas of high iodine uptake
Causes of the different types of primary hypothyroidism?
Goitrous:
• Chronic thyroiditis (AKA Hashimoto’s thyroiditis)
• Iodine deficiency
Non-goitrous:
• Congenital development defect
• Atrophic thyroiditis
Self-limiting:
• Withdrawal of suppressive thyroid therapy
• Sub-acute thyroiditis and chronic thyroiditis (transient hypothyroidism)
• Post-partum thyroiditis
What is chronic/Hashimoto’s thyroiditis?
Hereditary biosynthetic defect that is maternally transmitted and is an autoimmune disease of the thyroid gland
Causes of iodine deficiency?
Can be drug-induced:
• Amiodarone is a common culprit
• Lithium
• IL-2 and IFN-α
What is atrophic thyroiditis?
Can be:
• Post-ablative, e.g: due to radioiodine or surgery
• Post-radiation, e.g: for a lymphoma
Hypothalamic causes of secondary hypothyroidism?
Congenital
Infection, e.g: encephalitis
Infiltration, e.g: in sarcoidosis
Malignancy, e.g: caraniopharyngioma
Pituitary causes of secondary hypothyroidism?
Panhypopituitarism: • Trauma • Infection, e.g: TB, pituitary abscess • Infilitration, e.g: sarcoidosis, haemochromatosis, etc • Neoplasm, e.g: pituitary tumours
Histiocytosis:
• Neoplasms, e.g: pituitary and parapituitary tumours
Pituitary metastatic depositis
Isolated TSH deficiency
What is autoimmune hypothyroidism?
AKA Hashimoto’s thyroiditis
Most common cause of hypothyroidism and is autoimmune destruction of the thyroid gland, resulting in reduced thyroid hormone production
Occurrence of autoimmune hypothyroidism?
FH of thyroid/autoimmune disease
Females more commonly affected than males
Diagnosis of autoimmune hypothyroidism?
Presence of thyroid peroxidase antibodies in the blood
T-cell infiltrate and inflammation on microscopy
Progression of hypothyroidism?
Tends to progress over many years from:
- Euthyroid
- Mild thyroid failure (with T3 and T4 starting to decrease and TSH starting to increase)
- Overt hypothyroidism (with T3 and T4 dramatically reduced and TSH increased)
General signs and symptoms of hypothyroidism?
Hair - coarse and sparse
Thermogenesis - cold intolerance
Fluid retention - pitting oedema
Face:
• Dull, expressionless face
• Peri-orbital puffiness
• Xanthelasma (due to hyperlipidaemia)
Skin:
• Pale, cool skin that feels doughy
• Vitiligo may be present
• Hypercarotenaemia (increased beta-carotene causes yellow pigmentation of skin)
Cardiac signs and complications of hypothyroidism?
Reduced HR
Cardiac dilatation
Pericardial effusion
Worsening of heart failure
Signs of affected metabolic rate in hypothyroidism?
Decreased appetite
Weight gain
GI signs of hypothyroidism?
Constipation
Megacolon and intestinal obstruction
Ascites
Respiratory signs of hypothyroidism?
Deep hoarse voice
Macroglossia (big tongue)
Obstructive sleep apnoea
Neurological/CNS signs and complications of hypothyroidism?
Decreased intellectual and motor activities
Depression, psychosis, neuro-psychiatric problems
Muscle stiffness, cramps
Peripheral neuropathy
Prolongation of the tendon jerks
Carpal Tunnel Syndrome
(Cerebellar Ataxia, Encephalopathy)
Decreased Visual Acuity
Gynae/reproduction signs and complications of hypothyroidism?
Menorrhagia (heavy periods) and then, later on, oligo- or amenorrhoea
Hyperprolactinaemia (↑ TRH causes ↑ prolactin secretion)
Other Ix for hypothyroidism?
Macrocytosis is typical
Vitamin B12 (to rule out a concurrent deficiency)
Elevated creatinine kinase
Increased LDL cholesterol
Hyponatraemia (reduced renal tubular water loss); can occur less commonly due to co-existing cortisol deficiency
Hyperprolactinaemia (increased TRH increases prolactin secretion)
Antibodies present in Autoimmune hypothyroidism?
Anti-TPO (thyroperoxidase) Ab (best test)
Anti-thyroglobulin Ab
TSH receptor Ab
Mx of hypothyroidism?
Normal metabolic rate restored GRADUALLY:
• Younger patients - start thyroxine at 50-100μg daily
• Older patients with a PMH of IHD - start thyroxine at 25-50μg daily and adjust every 4 weeks based on response
In pregnancy, dose requirements may increase by 25-50%, due to increase in thyroid binding globulin (TBG)
Preferably taken before breakfast
Cautions with thyroixine use?
Check TSH 2 months after any dose change
Once stabilised, TSH should be checked once every 12 – 18 months
Complications of restoring normal metabolic rate too quickly?
May precipitate cardiac arrhythmias; particular care must be taken in elderly patients
What is the main treatment in hypothyroidism?
Thyroxine (T4)
Why is T3 therapy rarely used?
Has a short 1/2-life
Monitoring of therapy in primary hypothyroidism?
TSH reflects tissue thyroid hormone actions; TSH is an index of therapeutic success and potential toxicity
Monitoring of therapy in secondary hypothyroidism?
TSH is not as useful (remains lows if T4 therapy is commenced)
Instead, T4 is used to monitor treatment
Occurrence of myxoedema coma?
Tends to affect elderly women with long-standing but frequently unrecognized OR untreated hypothyroidism
Mortality is high
Investigation findings in myxoedema coma?
ECG: • Bradycardia • Low voltage complexes • Varying degrees of heart block • T wave inversion • Prolongation of the QT interval
Type 2 respiratory failure (hypoxia, hypercarbia, respiratory acidosis)
Co-existing adrenal failure is present in 10% of patients
Treatment of myxoedema coma?
Intensive care (ABC)
Passively rewarm (aim for a slow in body temp)
Monitor for arrhythmias, BP, CVP, oxygenation, urine output, blood glucose levels, electrolytes
Fluids OR fluid restriction
Broad spectrum antibiotics
Thyroxine cautious; administer hydrocortisone
Cardiac signs of hyperthyroidism?
Palpitations
Increased risk of AF
Cardiac failure (rare), due to increased rate and force of contraction of the heart
Sympathetic signs of hyperthyroidism?
Tremor and sweating
CNS signs of hyperthyroidism?
Anxiety, nervousness, irritability, sleep disturbance
GI signs of hyperthyroidism?
Frequent, loss bowel movements (diarrhoea)
Visual signs of hyperthyroidism?
Lid retraction
Double vision
Eyes that bulge out or protrude (in patients with Grave’s disease)
Hair and nail signs in hyperthyroidism?
Brittle and thinning hair
Rapid fingernail growth
Reproductive signs in hyperthyroidism?
Menstrual cycle changes, inc. lighter bleeding and less frequent periods
Muscle signs in hyperthyroidism?
Muscle weakness, esp. thighs and upper arms
Metabolic signs of hyperthyroidism?
Weight loss despite increased appetitie
Thermogenesis signs of hyperthyroidism?
Intolerance of heat
Causes of hyperthyroidism?
Autoimmune:
• Graves disease
Nodular thyroid:
• Multi-nodular goitre
• Toxic nodule (adenoma)
Thyroiditis (inflammation):
• Sub-acute
• Post-partum
Rarer causes of hyperthyroidism?
Iodine:
• From medications, e.g: amiodarone and thyroxine
• Supplements like kelp
Other medications, e.g: lithium, amiodarone and thyroxine
Occurrence of Grave’s disease?
More common in women and in younger people (20-50 years)
May have a +ve FH
May be related to high iodine intake, smoking
Ix results for Grave’s disease?
High T3/T4 and low TSH
Ab +ve (TSH receptor antibody is best)
Smooth symmetrical goitre shows with US and scintigraphy (shows symmetrical uptake)
Antibodies for Graves’s disease?
TSH-receptor Ab (best and more present than in autoimmune hypothyroidism)
Anti-thyroglobulin Ab
Anti-TPO Ab (2nd best)
Natural progression of Grave’s disease?
Varying course over 1 year but at 18 months:
• 50% will burn out
• 50% will relapse
Eye signs of Grave’s disease?
Grave’s opthalmopathy has signs of:
• Lid retraction
• Lid lag (not specific to Grave’s but occurs in hyperthyroidism)
• Chemosis (redness)
• Proptosis
• Visual loss (encroachment on optic nerve)
• Diplopia
Treatment of Grave’s opthalmopathy?
Depends on severity:
- Lubricants
- Decompression Surgery
- Radiotherapy
- Corrective Surgery
Smoking cessation
Presentation of nodular thyroid disease?
Occurs in older patients and has a more insidious onset
Gland may feel nodular
Ix results in modular thyroid disease?
High T3/T4 and low TSH
Ab -ve
Asymmetrical goitre shows with US and scintigraphy
What is thyroid storm?
Severe hyperthyroidism assoc. with:
• Respiratory and cardiac collapse
• Hyperthermia
• Exaggerated reflexes
There may be an assoc. underlying infection
Treatment of thyroid storm?
EMERGENCY (ABC): • Lugols iodine • Glucocorticoids (calm systemic inflammatory response) • PTU • β-blockers • Fluids
Must monitor frequently
It may require ventilation
Treatment options for hyperthyroidism?
• Carbimazole
• Propylthiouracil (preferred in pregnancy)
In Graves, start at a high dose and reduced over 12-18 months before stopping (50% chance of relapsing)
- Can give β-blockers for symptomatic treatment
- Radio-iodine
- Surgery (thyroidectomy)
Side effect of both carbimazole and propylthiouracil?
Risk of agranulocytosis; advise them to see doctor if they develop a febrile illness
Precautions with radio-iodine use?
Patient becomes slightly radioactive so:
• Avoid close prolonged contact with young children/pregnant women
• Do not share a bed for a certain no. of weeks/days
• Avoid pregnancy for 6 months and ensure not pregnant
Risk with radio-iodine use?
High risk of hypothyroidism (esp. in Grave’s)
Risks with surgery?
Scar
Surgical/anaesthetic risks, inc. recurrent laryngeal nerve palsy
Hypothyroidism
Hypo-parathyroidism
Types of thyroiditis?
Grave’s
Hashimoto’s
DeQuervain’s/subacute (viral)
Post-partum
Drug-induced (amiodarone, lithium) and radiation thyroiditis
Acute thyroiditis/suppurative (bacterial)
Presentation of sub-acute thyroiditis/De Quervain’s?
More common in females than males; tends to be 20-50 years
As it may be viral triggered it may be assoc. with a sore throat/fever/other viral symptoms
Treatment of sub-acute thyroiditis/DeQuervains’s?
Usually self-limiting (over a few months)
Ix results in sub-acute thyroiditis/DeQuervain’s?
T4 is high in early stages and low in late before becoming normal
TSH is low in early stages, high in late before becoming normal
Scintigraphy scan shows LOW UPTAKE
Occurrence of amiodarone-induced thyroid dysfunction?
Can occur in up to 1/2 of patients on the drug
Some develop hypothyroidism (amiodarone-induced thyrotoxicosis occurs more frequently in areas with low iodine intake)
Thyrotoxicosis can occur but less commonly (amiodarone-induced hypothyroidism occurs more frequently in areas with high iodine intake)
Ix results in SUB-CLINICAL hyperthyroidism?
There is a mildly overactive thyroid:
• TSH low
• T4/T3 normal
Ix results in SUB-CLINICAL hypothyroidism?
There is a failing thyroid gland:
• TSH high
• T4/T3 normal
