Endocrine Abstracts

Background: Hypothyroidism, a common condition, manifests with diverse clinical symptoms and is generally manageable but can be life-threatening if untreated in severe cases. It has been recognized as an uncommon cause of renal impairment and rhabdomyolysis; conditions reversible with levothyroxine replacement therapy. Here, we present the case of a teenager incidentally diagnosed with severe primary hypothyroidism due to autoimmune thyroiditis, accompanied by acute kidney injury (AKI), myositis, and pancreatitis, all of which improved with appropriate treatment.

Case report: A 14-year and 9-month-old boy presented to the gastroenterology team with a two-month history of recurrent epigastric pain. He reported significant weight gain and extreme fatigue over the past year. Clinical examination revealed obesity (BMI 32.4 kg/m², +2.99 SDS), hypotonia, dull facial expressions with periorbital oedema, and slow speech, with stable cardiovascular status. A barium meal study confirmed severe gastroesophageal reflux disease, leading to the initiation of Proton Pump Inhibitors. Biochemical investigations showed elevated creatine kinase levels, AKI, rhabdomyolysis, hepatitis, pancreatitis, and anaemia. Subsequent thyroid function tests confirmed primary hypothyroidism due to autoimmune thyroiditis, indicated by undetectable free T4 (<3.9 pmol/l), markedly elevated thyroid-stimulating hormone (250 mU/ml), and positive anti-TPO antibodies. Despite extensive investigations, no other clear cause for his conditions was identified except for a dysplastic small right kidney found on renal ultrasound. Therefore, the diagnosis of severe, long-standing primary hypothyroidism causing AKI secondary to rhabdomyolysis was established. Levothyroxine replacement therapy was cautiously initiated at a low dose (50 mg daily) to minimize the risk of atrial fibrillation. The dose was gradually increased to 125 mg daily, achieving euthyroid status. Importantly, starting thyroid hormone replacement therapy led to rapid resolution of myositis, hepatitis, pancreatitis, and significant improvement in renal function.

Conclusion: Delayed diagnosis of primary hypothyroidism can lead to complex and life-threatening presentations, including AKI secondary to hypothyroidism-induced myopathy and rhabdomyolysis. Hypothyroidism should be considered in patients presenting with decreased renal function and elevated creatine kinase in the absence of other causes of rhabdomyolysis. Initiation of treatment in severe primary hypothyroidism cases should be gradual and closely monitored to achieve euthyroidism while minimizing the risk of atrial fibrillation.