Endocrine Abstracts

Introduction: Graves’ disease is one of the leading causes for hyperthyroidism, worldwide. Complications include arrhythmias, osteoporosis and ophthalmopathy. Graves’ myopathy is not frequently encountered and sometimes overlooked.

Case Presentation: A 73-year-old female presented with leg swelling, difficulty getting up and mobilising. She had severe myalgia in proximal muscles and history consistent with proximal myopathy. Examination revealed mild bilateral exophthalmos and features of chronic venous insufficiency over legs. Power was reduced in proximal muscles. Blood tests revealed: TSH <0.01mU/l, FT4 39 pmol/l. Both TPO and TRAb were raised: >600IU/mL and 17.40 U/l, respectively. NT-pro BNP and CK normal. Notably, her potassium was normal. Venous doppler revealed DVT of the right leg. EMG showed proximal myopathic changes with early recruitment pattern, supportive of mild non-muscle irritable myopathy, keeping with thyrotoxic myopathy. After commencing Carbimazole, her symptoms improved. She was able to mobilise with ongoing physiotherapy. Neurology agreed with “thyrotoxic myopathy”. She received DOAC for DVT. She is back to her baseline mobility, with TSH <0.01, FT4 14.4 and FT3 6.73.

Discussion: While some patients with Graves’s disease treated with thionamides may manifest myalgia and rhabdomyolysis (usually associated with rapid thyroid hormone reduction), thyrotoxic myopathy rarely is associated with elevated CK and occurs due to accelerated muscle protein catabolism. Thyrotoxic myopathy is a distinct entity that presents with weakness and muscle wasting, unlike Thyrotoxic Periodic Paralysis (episodes of temporary paralysis and hypokalaemia). Symptoms usually resolve with treatment of underlying hyperthyroidism. Furthermore, hyperthyroidism also promotes a pro-coagulant state by enhancing activity of FVIII and vWF and autoantibody mediated platelet activation.

Conclusion: This case represents an atypical presentation of Graves disease where the patient did not have any of the classical symptoms of hyperthyroidism. When a patient presents with proximal myopathy, a thyroid myopathy should be considered as a differential.