[37] Acquired Hypothyroidism Flashcards
Is acquired hypothyroidism common?
Relatively
What is acquired hypothyroidism?
A condition where the thyroid gland makes insufficient thyroid hormone
What is primary hypothyroidism due to?
Inadequate function of the gland itself
What is secondary hypothyroidism due to?
A problem upstream of the thyroid gland
What problems upstream of the thyroid gland can cause secondary hypothyroidism?
- Inadequate stimulation by TSH from the pituitary gland
- Inadequate release of thyrotropin-releasing hormone from the brain’s hypothalamus
How much more common is primary hypothyroidism than secondary hypothyroidism?
1000x
What are the causes of primary hypothyroidism?
- Autoimmune
- Iodine deficiency
- Subacute thyroiditis
- Drugs
- Post-irradiation
- Post-ablative
What are the autoimmune causes of primary hypothyroidism?
- Hashimoto’s
- Chronic lymphocytic thyroiditis
Give two examples of drugs that can cause hypothyroidism
- Amiodarone
- Lithium
Give two causes of ablative hypothyroidism
- Radioiodine therapy
- Surgery
What will be found on blood tests in central hypothyroidism?
- Low serum TSH
- Low T4
What are the causes of central hypothyroidism?
- Intracranial tumour/mass
- Post cranial radiotherapy/surgery
- Developmental pituitary defects
What is the problem with the diagnosis of acquired hypothyroidism?
The symptoms and signs and usually insidious, and can be extremely difficult to diagnose clinically
What is the result of the signs and symptoms of acquired hypothyroidism usually appearing insidiously?
A high index of suspicion is required
What are the symptoms of acquired hypothyroidism?
- Dry skin
- Constipation
- Delayed puberty/amennorhoea
- Poor concentration and deterioration in school work
What are the signs of acquired hypothyroidism?
- Cold intolerance
- Thin, dry hair
- Bradycardia
- Cold peripheries
- Goitre
- Slow-relaxing reflexes
- Slipped upper femoral epiphysis
- Short stature/poor growth
What investigations should be done in acquired hypothyroidism?
- Thyroid function tests
- Thyroid antibody screen
What might the thyroid antibody screen show in acquired hypothyroidism?
Raised antibody titres for;
- Anti-thyroid peroxidase
- Anti-thyroglobulin
- TSH receptor (blocking type)
What are the differential diagnoses for acquired hypothyroidism?
- Other causes of short stature
- Other causes of fall-off in growth
- Other causes of goitre
How is acquired hypothyroidism managed?
Oral levothyroxine 25-200micrograms/day
What monitoring is required in acquired hypothyroidism?
Need to monitor TFTs every 4-6 months during childhood, and monitor growth and neurodevelopment
What are the complications of acquired hypothyroidism?
Increased risk of developing other autoimmune disorders, e.g. vitiligo, RA
