Endocrine Abstracts

Introduction: Glycogen storage disease type 1a (GSD1a) is an inborn error of metabolism with several metabolic decompensations including anaerobic glycolysis and lactic acidosis but few known about GSD1a-related hypercalcemia. Here we aimed to present a putative relationship between serum Ca and the affected metabolic parameters during metabolic decompensation of GSD1a.

Case report: Two patients with GSD1a and hypercalcemia were retrospectively analyzed. Fasting plasma glucose, serum calcium (Ca), triglyceride (TG), lactate and HCO3 levels were documented as the markers for metabolic control. Corrected/ionized Ca ratio was used as an indirect marker of serum unbound calcium fraction other than ionized calcium.

Case 1 is a 19-year-old male, diagnosed of GSD1a at the age of eight. Case 2 is 32-year-old female, diagnosed as GSD1a at the age of three. Ionized-Ca levels were normal in both patients despite high levels of the corrected serum Ca and low PTH levels. When the levels of corrected serum Ca matched with fasting plasma glucose, serum TG, lactate and HCO3 levels, a positive correlation between serum Ca and TG levels was observed.

Conclusion: Hypercalcemia in GSD1a might be simply related to an erroneous measurement due to high triglyceride levels. However, it cannot explain PTH-supression. The Corrected/ionized Ca ratio was negatively correlated with PTH levels. During the course of chronic lactic acidosis, bone works as a buffer-tissue by mobilizing CaCO3. Therefore slightly high calcium levels suppressing PTH may be related to release of calcium from the bone tissue. Consequently mild hypercalcemia itself may be a sign of metabolic decompensation like high triglyceride levels in patients with GSD1a.