MI. Alexandre*a (Dr), JV. Rochaa (Dr), AC. Gomesa (Dr)

a Hospital de Santa Maria, CHULN, Lisboa, PORTUGAL

* mariaines.f.alexandre@gmail.com

Introduction: MEN-1 is a rare genetic disorder that predisposes patients to primary hyperparathyroidism, duodeno-pancreatic neuroendocrine tumours and pituitary tumours. We present the case of a patient whose initial diagnostic workup suggested MEN-1, however it was not confirmed.

Observations: A 40-year-old woman was referred to our endocrinology outpatient clinic with hypoglycemia, suspected hyperparathyroidism and pituitary adenoma. She had also been recently diagnosed with Graves’ disease. At her first appointment, blood tests, which were done 3 weeks after starting thiamazole, showed hyperthyroidism with positive TSH receptor antibodies (TRAbs) and revealed a blood glucose of 39 mg/dL associated with elevated insulin levels (100 mIU/L; N:2,6-24,9) and elevated PTH (125 pg/mL; N:10-55). The cranial CT-scan, performed during an episode of hypoglycemia-associated confusion, revealed a small area of hypocaptation in the pituitary that suggested a possible microadenoma.

The association of these problems suggested a MEN-1 phenotype with insulinoma, hyperparathyroidism and pituitary adenoma, so a more thorough investigation was initiated. Regarding hypoglycemia, the episodes only begun after initiating thiamazole. Additional workup revealed high titers of insulin autoantibodies and there was no image suggestive of insulinoma in the abdominal CT. The diagnosis of insulin autoimmune syndrome (IAS) triggered by thiamazole was assumed. As the patient started on prednisolone and thiamazole was gradually reduced, these episodes resolved. Regarding the elevated PTH, additional blood tests revealed a normal serum calcium and phosphorus and low 25-hydroxyvitamin D, so the diagnosis of secondary hyperparathyroidism was made and the patient was successfully treated with cholecalciferol. Concerning the suspected pituitary adenoma, MRI revealed a normal pituitary and pituitary function blood tests were all normal.

Discussion: IAS is a rare condition characterized by hypoglycemia and autoantibodies directed towards insulin. The thiamazole-related autoimmunity has been reported previously, mostly in Japan. What is particular about this case is the association between this rare condition and other features that could mislead into the diagnosis of MEN-1. This highlights the importance of a detailed anamnesis and to carefully access the need for some complementary exams, as some incidental findings can lead to unnecessary costly exams and worries.

The author has declared no conflict of interest.