20/07/2013 by admin | Endocrine
  1. Due to increased circulating free levels of thyroid hormones (T3 and T4).
  2. F>M (5>1). Most common in middle ages. Prevalence = 2%
  3. Causes:
  4. Most common cause = autoimmune disease (Graves, TNG, and toxic adenoma)
    1. o Graves’ disease: 75% of all cases. Due to antibodies interacting with immunoglobulin IgG TSH receptors with the thyroid gland TSH receptor = leading to thyroid gland stimulation, increased T4 secretion, thyroid growth.
    2. o Linked to graves is eye disease = ophthalmopathy and organ specific autoimmune disease.
    3. o Toxic multinodular goitre (TNG): 15% cases. May develop in to longstanding goitre. Will have relapses after anti-thyroid drug therapy – so definitive surgery/RT required.
    4. o Toxic adenoma (single nodular goitre): 5% of cases, an autonomous hyper-functioning nodule that produces excess thyroid hormones and supresses TSH secretion.
    1. o Hashimoto’s thyroiditis: autoimmune (=thyroid peroxidase antibody related)! smooth thyroid enlargement, may produce hyper- then hypothyroidism.
    2. o Postpartum thyroiditis: usually self-limiting
    3. o Rare causes:
    4. Viral (De Quervain’s thyroiditis)
    5. Drugs (amiodarone, thyroxine, iodine excess [=Jod-Basedow effect])
    6. Hypothalamic-pituitary disease (TSH secreting tumour or pituitary resistance to thyroid hormones)
    7. Hyperemesis gravidarum (hCG-mediated stimulation of thyroid)
    8. Factitious
    9. Ovarian tumour (sertoli cell)
  1. p/c: anxiety, irritability, palpitations, weight loss, heat intolerance, increased sweating, goitre +/- bruit, fine tremor, menstrual disturbance, proximal myopathy (difficulty on stairs/reaching top shelf), AF (increased risk in men ~x2, and with increasing age), CMPs, raised JVP, tachycardia, diarrhoea, pretibial myxoedema (infiltration with mucopolysaccharides – giving a waxy indurated discoloured peau d’orange appearance)
  2. Eye signs (=proptosis, exopthlamus, retracted eye lids and cornea exposure (=corneal ulcers = blindness), lid lag, traction on optic nerve, swollen extra-ocular muscles. Eye signs present in 50% of pts at presentation and increased risk in smokers.
  3. Ix:
    1. o TFT: increased T4 and T3, decreased TSH = primary hyperthyroidism
    2. o Thyroid antibodies: thyroid peroxidase and anti-thyroglobulin = autoimmune aetiology
    3. o Imaging (99Technetium Scan) = thyroid uptake scan differentiates between Grave’s (diffusely increased uptake) from TNG (multiple hot spots) and toxic adenoma (single hot spot).
  4. Mx:
    1. o Drug: regardless of diagnosis – start on carbimazole 40-60mg/d, reduce this down to a maintenance dose later on.
    2. o Dose is titrated according to thyroid function and continued for 18/12 after which 50% of Grave’s pts are cured
    3. o Alternative approach = large dose of carbimazole with T4 to avoid hypothyroidism (‘block and replace’ technique).
    4. o Carbimazole can cause agranulocytosis in 0.1% – STOP immediately if sore throat/fever occur
    5. o Avoid carbimazole in pregnancy – safe alternative = Propylthiouracil
  5. Surgery:
    1. o Thyroidectomy for TNG, toxic adenoma, or relapses of Grave’s after anti-thyroid drug therapy
    2. o Specific risks of surgery include: vocal cord palsy (RLN damage), hypothyroidism, and hypoparathyroidism
  6. Radio-iodine: concentrates in thyroid gland and so destroys thyroid tissue. Anti-thyroid drugs are stopped 7-10 d prior to administration to allow uptake of radio-iodine.
    1. o Occasionally repeated disease are required (3 x max in lifetime).
    2. o S/e: worsening of thyroid eye disease, transient/permanent hypothyroidism (50% at 10 years), thyrotoxic crisis (if hyperthyroidism poorly controlled before administration), pain.
  7. Tx for thyroid-associated ophthalmopathy:
    1. o Supportive = elevate head of bed, artificial tears, prismatic glasses for diplopia
    2. o Definitive = high dose steroids +/- immunosuppression to decompress orbit, surgical orbital decompression or orbital RT.
  8. Thyroid Storm:
  1. o Rare, life-threatening (mortality 10%)
  2. o p/c: fever, anxiety, agitation, confusion, tachycardia, occasionally heart failure.
  3. o Mx: carbimazole 10-120mg or propylthiouracil and potassium iodide (reduces thyroid vascularity), b-blockers (propranolol) reduces adrenergic features and inhibit conversion of T4T3. Glucocorticoids, suppuortive treatments, IV fluids, anti-pyretics.


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