Endocrine Abstracts

JOINT3996

Background: The association between diabetes mellitus and thyroid abnormalities is well established. However, a new-onset case of diabetes mellitus associated with severe hyperthyroidism poses a number of diagnostic and pathophysiological questions. We thus attempt to use this case to highlight the need to seek for an underlying autoimmune origin.

Case summary: A 52-year-old man, an active smoker with a family history of type 1 diabetes (T1DM) in both father and son, presented to the emergency department with a one month history of polyuria, polydipsia, polyphagia and significant weight loss. Physical examination revealed a fatigued patient with tachycardia at 120 beats/min, with no marked signs of thyrotoxicosis (exophthalmos, goitre). Finger glucose was 4.60 g/l. Urine examination showed two-cross glycosuria and one-cross ketonuria. Initial laboratory data revealed normal natraemia and kaliemia, alkaline reserves of 21 mmol/l, and creatinemia of 67 µmol/l. Glycated haemoglobin was 7.4%. New-onset diabetes with ketotic decompensation was diagnosed and the patient was admitted to emergency. An electrocardiogram confirmed the tachycardia. In parallel, thyroid function tests were performed. Decreased thyroid-stimulating hormone (0.005 µUI/l) and increased free thyroxine (84.4 pmol/l) confirmed the diagnosis of hyperthyroidism and anti–thyroid peroxidase autoantibodies were found to be markedly positive. In order to determine both the type of diabetes and the cause of the hyperthyroidism, we carried out an assay of antibodies (anti-glutamic acid decarboxylase (anti-GAD65), anti-TSH receptor), and a cervical ultrasound scan, which showed signs of hyperthyroidism. The patient was treated with insulin, synthetic antithyroid drugs (Thyrozol 3 tablets/day) and a beta-blocker to control the tachycardia.

Discussion: The coexistence of new onset diabetes and severe hyperthyroidism suggests a common autoimmune cause. The diagnosis of Latent autoimmune diabetes in adults ( LADA ) associated with basedow’s disease is the most likely in this family context of T1DM. Hyperthyroidism increases insulin resistance and exacerbates diabetes, requiring adjustment of insulin therapy. Early identification of anti-GAD and anti-TSH receptor antibodies is extremely important in order to adjust treatment and prevent complications.

Conclusion: This case highlights the importance of a rigorous assessment of associated endocrine disorders in a patient with newly diagnosed diabetes. Screening for associated autoimmune diseases allows more appropriate management and better prediction of complications.