Endocrine Abstracts

Postural orthostatic tachycardia syndrome (PoTS) occurs as a consequence of the abnormal functioning of the autonomic nervous system (dysautonomia). Despite the many associated conditions, the assessment and relationship to reactive hypoglycaemia has not been explored in the clinical literature.

The purpose of this retrospective observational-cohort study was to identify relationships between the physical and biochemical characteristics in potential carbohydrate metabolic disorders in individuals diagnosed with PoTS. This study used a standard prolonged oral glucose tolerance test (POGTT) over 5 hours.

Seventeen individuals were tested, with a mean age of 27.23 years; one patient was unable to complete the test due to an intense and significant response to the sugar load; 41% achieved peak glucose levels at 30 minutes and 57% attained nadir glucose (ranges: 1.8–3.4 mmol/L) between 210–240 minutes. Fasting insulin levels were noted in 30% of individuals, cortisol levels at baseline were adequate and unremarkable. Joint hypermobility (29%), Inappropriate Sinus Tachycardia (31%) and Chronic Fatigue (22%) were additional associated conditions represented within the study group.

The data collected from this small study suggests a strong relationship between PoTS and carbohydrate metabolic dysfunction. We observed that patients exhibited a biphasic response with symptoms related to the both the nadir glucose and the large changes in blood glucose that were independent of the recorded glucose level. Significant symptoms occurred despite only 60% achieving a nadir glucose of 3.0 mmol/L; with a considerable number of these patients exhibiting a substantial improvement in symptoms with dietary changes to address reactive hypoglycaemia.

Our study is hampered by the small number and homogeneity of our participants; however our results underpin the recommendations of a low carbohydrate diet with the consumption of meals every 2–3 hours for the stabilisation of blood glucose values and an improvement to symptoms.