Hypothyroidism

Causes

• Iodine deficiency (rare in Singapore)
• Autoimmune disease (Hashimoto’s thyroiditis, primary myxedema). Associated:
  • Addison’s disease
  • Diabetes mellitus
  • Graves’ disease
  • Vitiligo
  • Addison’s disease
  • Pernicious anaemia
  • Hypoparathyroidism
  • Systemic lupus erythematosus
  • Rheumatoid arthritis
• Iatrogenic
  • Radioiodine ablation for hyperthyroidism
  • Sub-total / total thyroidectomy
  • Radiotherapy for lymphoma / head and neck cancer
• Drugs
  • Amiodarone
  • Lithium
  • Anti-thyroid drugs
  • Sunitinib
• Destructive thyroiditis
  • Post-partum thyroiditis
  • Sub-acute thyroiditis
• Infiltrative disorders
  • Amyloidosis
  • Sarcoidosis
  • Haemochromatosis
  • Riedel’s thyroiditis (fibrotic thyroid infiltration)
  • Scleroderma
• Secondary hypothyroidism (low TSH, low T4)
  • Pituitary tumour
  • Brain trauma
  • Pituitary surgery / irradiation
  • Pituitary infarction

History

• Symptoms of hypothyroidism
  • Tiredness
  • Difficulty climbing stairs, standing up from sitting position
  • Change in facial appearance
  • Cold intolerance
  • Dry hair, thinning of hair
  • Poor memory and concentration
  • Constipation
  • Voice hoarseness
  • Weight gain, poor appetite
  • Menorrhagia / impotence
  • Paraesthesia
  • Deafness
  • Depression / psychosis
• Secondary causes
  • Drugs list
  • Bumping into things unintentionally
  • Headache
  • Lump in neck
  • Burnt out Graves’
    • Ever had hyperthyroidism
    • Ever had heat intolerance, weight loss, palpitations, diarrhoea
  • Previous neck surgery, radiation to neck
• Related conditions
  • Diabetes
  • Postural symptoms (Addison’s)
• Complications
  • Carpal tunnel syndrome
    • Numbness / tingling of palm
    • Thumb weakness
    • Wrist pain
  • Heart failure
    • Exertional dyspnea
    • Orthopnoea / PND
  • Goitre
    • Airway compression – stridor?
    • Dysphagia
  • For treatment purposes
    • History of IHD
    • Age

Physical examination

• Inspection:
  • Peri-orbital oedema
  • Coarse, thin hair
  • Dry skin
  • Loss of outer third of eyebrow
  • Hoarse voice
  • Elevated body mass index
• Peripheries
  • Pulse (bradycardia)
  • Tinnel’s test (carpal tunnel syndrome)
• Examine neck for goitre, scar suggesting previous thyroidectomy
• Cardiovascular system for heart failure
  • Pulse: bradycardia
  • Raised JVP
  • Displaced apex beat
  • Bibasal crepitations
  • Peripheral oedema
• Neurological system
  • Proximal weakness
  • Slow-relaxing reflexes
  • Cerebellar signs
• Eyes (burnt-out Graves’)
  • Exophthalmos
  • Ophthalmoplegia
  • Relative afferent pupillary defect

 Counselling

• Diagnosis: low levels of thyroid hormone, which controls your metabolism – energy levels
• Can manage as an outpatient (unless in myxedema coma)
• Will need to do some tests to confirm the diagnosis
  • Blood tests for thyroid hormone levels
  • Electrical recording of the heart
• Treatable condition, which involves replacing hormone levels
  • Will start at a small dose
  • Please take two hours before meals, as it can affect absorption
  • If you experience any symptoms like chest pain or breathlessness with exercise, please do give the clinic a call immediately
• Manage with a few of my colleagues
  • Endocrinologist, specialist in this area
  • Physiotherapy, to help with strengthening exercises
  • Orthopaedic surgeon for carpal tunnel syndrome
• If pregnant
  • Can slow fetal development
  • Increased risk of placental abruption, pre-eclampsia
  • Will need more replacement during pregnancy
• Monitoring and follow-up: 2-monthly TFT and titrate levothyroxine according to TSH

Presentation

This patient has hypothyroidism. He complains of cold intolerance, constipation, lower limb weakness and lethargy. There is an elevated body mass index, dry skin coarsened hair which is thinning, peri-orbital oedema and a hoarse voice. There is proximal 4/5 weakness in all four limbs, and the reflexes are slow-relaxing throughout. There are no signs of heart failure and he is not bradycardic.

There was no surgical scar to suggest previous thyroid surgery, signs of thyroid eye disease to suggest previous Graves’ disease or signs of associated autoimmune conditions. Examination of her medication list did not yield any drugs known to cause hypothyroidism

In summary, this patient has hypothyroidism, which is most likely due to Hashimoto’s thyroiditis