Thyrotoxicosis

Background

Thyrotoxicosis causes

• Commonest is Graves disease (auto Ab to TSH receptor with XS T4 and reduced TSH from pituitary)
• Thyroid adenoma (or rarely carcinoma)
• Toxic multi-nodular goitre
• TRH producing pituitary adenoma
• Iodine or amiodarone administration
• 1% of thyrotoxic pushed by trigger (AMI, meds change, sepsis, surgery etc.) into thyroid storm (30 - 60yo)

Differential Dx

• CCF
• Heatstroke
• Neuroleptic malig syndrome (NMS)
• Septicaemia
• Serotonin syndrome
• Anticholinergic toxicity
• Cocaine or similar

Thyroid storm

• Life threatening hyper-metabolic state
• Clinical Dx
• Wt loss, tachyarrhythmias, alopecia, eye abnormalities etc
• Hyper-metabolic state (pyrexia, hypertension, tachycardia [AF], tachypnoea, CCF, eye signs, hyperglycaemia)
• Low TSH, high T3 T4
• Look for precipitating cause (particularly sepsis)
• Beware CCF (arrhythmia, persistent hypertension, cardiomyopathy)

General approach to Mx

• Target each T4 synthesis step
• Propylthiouracil (PTU) (inhibits hormone synthesis and T4 to T3 conversion)
• Β blockers (traditionally propanolol but cardioselective may be safer in COPD/asthma etc) inhibit target organ effects and inhibit conversion T4 to T3
• Iodine inhibits T4 release from gland: but must not be given before PTU as it may stimulate T4 release
• Avoid Aspirin (unbinds T4 from plasma proteins)

Storm Management