A Case of Persistent Hypoglycemia: When to Think Outside the Box

Abstract

A 71-year-old Chinese woman with autoimmune Hashimoto's hypothyroidism and mixed connective tissue disease (MCTD) was referred to the Endocrine Unit for frequent episodes of hypoglycemia. The patient was diagnosed with diabetes by her general practitioner several weeks earlier and started on metformin for symptoms of polyuria, polydipsia, and a random blood glucose level of 468 mg/dl. The hyperglycemia was initially thought to be secondary to initiation and subsequent increase in dose of the steroid used for treatment of her MCTD. A week after taking metformin, she noted increased episodes of palpitations, dizziness, and diaphoresis, which were relieved with food intake. She subsequently decided for herself to discontinue the metformin. Her fasting capillary blood glucose readings were 44–55 mg/dl. Hypoglycemia occurred despite constant and pre-planned food intake. Additionally, these episodes of hypoglycemia became more frequent with discontinuation of her oral hydroxychloroquine (because of skin hyperpigmentation) and steroids, and the hypoglycemia persisted until she sought medical care. During the patient's inpatient workup for hypoglycemia, numerous fasting capillary blood glucose readings ranged from 32 to 65 mg/dl, and 2-hour postprandial glucose readings were between 47 and 61 mg/dl. These readings were confirmed with measurements of serum blood glucose. The patient's A1C was 5.7%. Because of her frequent and persistent hypoglycemic events, she was given a continuous dextrose drip and advised to eat frequent meals. Given her history of chronic steroid use, a low-dose adrenocorticotropic hormone stimulation test was performed to assess her hypothalamic-pituitary-adrenal axis; results were consistent with adrenal insufficiency. She was then placed on daily replacement doses of hydrocortisone, 10 mg every morning and 5 mg every evening. Despite having steroid replacement, taking frequent meals, and being on a 10% continuous dextrose drip, her hypoglycemia continued. There was no history of insulin use. During inpatient monitoring, there was no evidence to suggest …