HYPOTHYROIDISM

THE GREAT MIMICKER

Abstract

INTRODUCTION
Hypothyroidism is a common endocrinopathy presenting with an assortment of well-described symptoms and signs. Less commonly, myopathy may be the sole presenting manifestation, making it perplexing to ascertain the diagnosis from other systemic and local aetiologies. This is a case of severe hypothyroidism which had manifested itself in the form of persistently raised creatine kinase (CK) following a presumed episode of non-ST elevation myocardial infarction (NSTEMI).

CASE
A 57-year-old gentleman first presented to a district hospital in December 2016 with atypical chest pain. His electrocardiogram showed T-wave inversion over leads V2 to V6, I and AVL. Along with his raised CK (3,448 U/L), the impression then was NSTEMI and he was treated accordingly. Throughout his admission, his CK showed a declining trend and was 2,481 U/L upon discharge. An echocardiogram revealed good ejection fraction of 65% with no regional wall motion abnormalities. However, during his subsequent visit, his CK did not normalise. Initial concern of statin-induced myopathy resulted in his statin being withheld. Nevertheless, his CK showed a further rise to 4,328 U/L in May 2017. Further history revealed symptoms of cold intolerance, fatigue and constipation, suggestive of hypothyroidism. He denied muscle aches or weakness and there was no demonstrable proximal myopathy. His subsequent thyroid function test demonstrated extremely high thyroid stimulating hormone (TSH) (>100 µIU/mL) with low free thyroxine (0.8 pmol/L). Following commencement of thyroxine replacement, his TSH (0.67 µIU/mL) and CK normalised.

CONCLUSION
In hypothyroidism, the involvement of skeletal muscles may vary, ranging from an asymptomatic rise in creatine kinase (CK) to overt muscle weakness. Because hypothyroidism can be a great mimicker, a high index of suspicion is imperative.