Imbalanced cortisol concentrations in glycogen storage disease type I: evidence for a possible link between endocrine regulation and metabolic derangement

BACKGROUND: Glycogen storage disease type I (GSDI) is an inborn error of carbohydrate metabolism caused by mutations of either the G6PC gene (GSDIa) or the SLC37A4 gene (GSDIb). Glucose 6-phosphate (G6P) availability has been shown to modulate 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), an ER-bound enzyme catalyzing the local conversion of inactive cortisone into active cortisol. Adrenal cortex assessment has never been performed in GSDI. The aim of the current study was to evaluate the adrenal cortex hormones levels in GSDI patients. METHODS: Seventeen GSDI (10 GSDIa and 7 GSDIb) patients and thirty-four age and sex-matched controls were enrolled. Baseline adrenal cortex hormones and biochemical markers of metabolic control serum levels were analyzed. Low dose ACTH stimulation test was also performed. RESULTS: Baseline cortisol serum levels were higher in GSDIa patients (p = 0.042) and lower in GSDIb patients (p = 0.041) than controls. GSDIa patients also showed higher peak cortisol response (p = 0.000) and Cortisol AUC (p = 0.029). In GSDIa patients, serum cholesterol (p = 0.000), triglycerides (p = 0.000), lactate (p = 0.000) and uric acid (p = 0.008) levels were higher and bicarbonate (p = 0.000) levels were lower than controls. In GSDIb patients, serum cholesterol levels (p = 0.016) were lower and lactate (p = 0.000) and uric acid (p = 0.000) levels were higher than controls. Baseline cortisol serum levels directly correlated with cholesterol (ρ = 0.65, p = 0.005) and triglycerides (ρ = 0.60, p = 0.012) serum levels in GSDI patients. CONCLUSIONS: The present study showed impaired cortisol levels in GSDI patients, with opposite trend between GSDIa and GSDIb. The otherwise preserved adrenal cortex function suggests that this finding might be secondary to local deregulation rather than hypothalamo-pituitary-adrenal axis dysfunction in GSDI patients. We hypothesize that 11βHSD1 might represent the link between endocrine regulation and metabolic derangement in GSDI, constituting new potential therapeutic target in GSDI patients.