PROLONGED HYPOTHYROIDISM AS A RARE COMPLICATION AFTER ANTITHYROID TREATMENT FOR A PATIENT PRESENTING WITH THYROID STORM

Abstract

INTRODUCTION/BACKGROUND
Hypothyroidism rarely occurs following anti-thyroid therapy (ATT). We present a case of prolonged hypothyroidism following ATT for thyroid storm.

CASE
A 50-year-old female presented to the emergency department with a 3-week history of failure symptoms, 10 kg weight loss and diarrhoea. She was in respiratory distress, hypotensive with a high fever and had atrial fibrillation in rapid ventricular response (170 beats/min) with congestive heart failure. She had no goitre or ophthalmopathy. She was diagnosed with thyroid storm (Burch-Wartofsky Score 90) with free T4 79.9 pmol/L and TSH <0.005IU/L. Despite prompt initiation of carbimazole, IV hydrocortisone, Lugol’s iodine, non-invasive ventilation, IV amiodarone and electrical cardioversion, she suffered cardiorespiratory arrest. She was revived after cardiorespiratory resuscitation, intubation and triple inotropic support. Her 21-day ICU stay was eventful with multiorgan failure (ischaemic hepatitis, cardiogenic shock, oliguric kidney injury) complicated by nosocomial infection, critical illness myopathy and bedsore. She spent three months in the hospital, including one month of inpatient rehabilitation. Thyroid-wise, she responded to ATT with fT4 dropping to 36 pmol/L on day 3 of admission. All ATT was discontinued on day 11 when fT4 was reduced to 3.64 pmol/L and TSH <0.005 IU/L. On Day 28, her fT4 remained suppressed, reaching a nadir of 1.36 pmol/L (TSH 0.084IU/L, fT3 1.60 pmol/L [normal 3.1–6.8 pmol/L]). Her fT4 rebounded to 47.80 pmol/L (TSH <0.005 IU/L) after 6 weeks (or one month from the last dose of carbimazole). Carbimazole was reintroduced and continued up to her recent follow-up at 2 months post-discharge.

CONCLUSION
Hypothyroidism can occur with ATT for primary hyperthyroidism due to overdosage or increased individual sensitivity, but it is usually short-lived. Prolonged hypothyroidism shortly after presentation of thyroid storm is unusual. Possible explanations include the presence of TSH blocking or stimulating antibodies, sick euthyroid syndrome and the elusive “shock thyroid.” A thyroid storm due to a thyrotoxic phase of thyroiditis is unlikely here due to the subsequent relapse of thyrotoxicosis. Careful clinical assessment and monitoring are essential to guide treatment direction.