Endocrine Abstracts

Introduction: Individuals with glycogen storage disease type 1b (GSD1b) usually have low blood glucose and are at constant risk of hypoglycemia. We recently hospitalized a pregnant woman with GSD1b, where despite nutritional management, her glycemia values were almost unwaveringly towards the lower physiological limits. In a recent study (Rossi et al. Orphanet Journal of Rare Diseases 2020; 15: 99, https://doi.org/10.1186/s13023-020-01377-w) it was reported that under resting conditions and after stimulation with corticotropin (ACTH), individuals with GSD1b (n:7) show lower cortisol levels compared to a control group.

Aim: Considering that the stimulus of hypoglycemia is strong for the hypothalamic-pituitary-adrenal (HPA) axis, we investigated the postpartum diurnal variation of salivary cortisol (sF) in a woman with GSD1b.

Methods: Postpartum, in a 35-year-old woman with GSD1b, we assessed the diurnal variation in sF (5 samples per day) for two days, the first week postpartum and after three months. Corresponding sampling was performed in two, age-matched healthy women, 2-4 months postpartum, who formed the control group. The sF determinations were performed using the Elecsys Cortisol II assay (Roche) with electrochemiluminescence. The Sign test was applied for statistical analysis.

Results: The diurnal profile of sF changes was similar in shape for the patient and control group, with a peak at wake-up and nadir at 20:00-midnight. Overall, the patient’s early sF measurements were higher than her late ones (P:0.03). The patient’s late sF measurements were higher than those of the control group on the first day (P:0.05). On the second day, the patient’s late cortisol awakening response (CAR, sF at 08:00 - sF at 08:30) was marginally lower, compared to the control group (P:0.06).

Discussion: The early sF measurements of the GSD1b patient point towards a stimulation of the HPA, however this is also a finding in normal women postpartum, where within a few days after delivery, plasma total and free F values gradually return to pre-pregnancy levels after increasing, especially in the third trimester of pregnancy (Jung et al J Clin Endocrinol Metab 2011; 96:1533-1540 & Mistry et al. Reproductive Biology and Endocrinology 2015; 13:101). According to our results, in GSD1b, no particular effect of the sustained stimulus of hypoglycemia on HPA is found.