Endocrine Abstracts

Introduction: Therapy with hydroxychloroquine (HCQ) and chloroquine (CQ) constitutes a rare but documented cause of hypoglycemia in non-diabetic adults. The physiopathological mechanism is not fully understood, and symptoms may appear several years after starting treatment. In this paper, we describe the clinical presentation and investigation of a case of hypoglycemia attributed to HCQ therapy.

Clinical Case: A 60-year-old female patient was referred for an Endocrinology consultation due to recurring symptomatic hypoglycemia (headache, tremors, nausea) documented by capillary blood glucose measurement at home. The patient had a history of Systemic Lupus Erythematosus with nephropathy, treated with HCQ, mycophenolate mofetil, and prednisolone, with no history of diabetes mellitus or insulin or sulfonylurea therapy. The patient underwent a 72 h-fasting test, which induced symptomatic hypoglycemia at 24 hours (48 mg/dl, confirmed by laboratory assay) without biochemically evident hyperinsulinism (Insulin 0.6 umol/l, C-peptide 0.3 ng/l). The remaining etiological study was negative: laboratory testing for adrenal function was normal (ACTH, Cortisol within normal range). Sulfonylurea dosing was negative, IGF-1, IGF2, and anti-insulin antibody levels were within normal limits. β-hydroxybutyrate levels were slightly elevated (1.10 mmol/ml). Thoracic and abdominal CT scan did not reveal morphological changes, most notably in the pancreas; 18F-FDOPA PET scan did not show areas of increased radionuclide uptake. Given the absence of aetiologically suggestive biochemical or structural findings, as well as the existence of reported cases of hypoglycemia secondary to HCQ therapy, a decision was made to discontinue the drug. To date (approximately 5 months), there has been complete absence of symptoms, with no recurrence of hypoglycemia.

Conclusion: Although a rare condition, hypoglycemia due to HCQ therapy should be considered as a possible aetiology in patients with proven hypoglycemia under this therapy.