Glycogen Storage Disease Type Ia: Current Management Options, Burden and Unmet Needs

Glycogen storage disease type Ia (GSDIa) is caused by defective glucose-6-phosphatase, a key enzyme in carbohydrate metabolism. Affected individuals cannot release glucose during fasting and accumulate excess glycogen and fat in the liver and kidney, putting them at risk of severe hypoglycaemia and secondary metabolic perturbations. Good glycaemic/metabolic control through strict dietary treatment and regular doses of uncooked cornstarch (UCCS) is essential for preventing hypoglycaemia and long-term complications. Dietary treatment has improved the prognosis for patients with GSDIa; however, the disease itself, its management and monitoring have significant physical, psychological and psychosocial burden on individuals and parents/caregivers. Hypoglycaemia risk persists if a single dose of UCCS is delayed/missed or in cases of gastrointestinal intolerance. UCCS therapy is imprecise, does not treat the cause of disease, may trigger secondary metabolic manifestations and may not prevent long-term complications. We review the importance of and challenges associated with achieving good glycaemic/metabolic control in individuals with GSDIa and how this should be balanced with age-specific psychosocial development towards independence, management of anxiety and preservation of quality of life (QoL). The unmet need for treatment strategies that address the cause of disease, restore glucose homeostasis, reduce the risk of hypoglycaemia/secondary metabolic perturbations and improve QoL is also discussed.

Cornstarch requirements of the adult glycogen storage disease Ia population: A retrospective review

Cornstarch has been the primary treatment for glycogen storage disease type Ia (GSD Ia) for over 35 years. When cornstarch was first described as a treatment, few people survived beyond early childhood. As the prognosis for this population has improved, the need to ensure appropriate cornstarch dosing for different age groups has become imperative. Records from 115 patients (10-62 years of age) with GSD Ia evaluated at our center between 2015 and 2017 were reviewed. Data collected included weight, age, genetic mutation, amount and frequency of cornstarch doses, body mass index, gender, 24-hour glucose and lactate concentrations, and biochemical markers of metabolic control. The data demonstrate that adult treatment needs vary greatly from younger age groups, and the required cornstarch support decreases with age (P < .001). The required number of doses, however, did not change with a mean of six doses (range 4-8) daily in all age groups. General laboratory findings across time demonstrate that significantly reducing the amount of starch required to maintain euglycemia with aging can be done without sacrificing metabolic control. Carbohydrate requirements decrease with aging, and older patients were found to require less cornstarch. Failure to lower the cornstarch doses contributes to over-treatment in adults with GSD Ia. Not only does this lead to worsening hepatomegaly and excessive weight gain, but over-treatment contributes to relative hyperinsulinism and rebound hypoglycemia. This knowledge is essential in designing nutritional therapies for the aging GSD population.

Glycemic control and complications in glycogen storage disease type I: Results from the Swiss registry

BACKGROUND

Regular carbohydrate intake to avoid hypoglycemia is the mainstay of dietary treatment in glycogen storage disease type I (GSDI). The aim of this study was to evaluate the quality of dietary treatment and glycemic control in a cohort of GSDI patients, in relation to the presence of typical long-term complications.

METHODS

Data of 25 patients (22 GSD subtype Ia and 3 GSDIb, median age 20y) from the Swiss hepatic glycogen storage disease registry was analyzed cross-sectionally. Frequency and type of hypoglycemia symptoms were assessed prospectively using a structured questionnaire. Diagnostic continuous glucose monitoring (CGM) was performed as part of usual clinical care to assess glycemic control in 14 patients, usually once per year with a mean duration of 6.2 ± 1.1 consecutive days per patient per measurement.

RESULTS

Although maintenance of euglycemia is the primary goal of dietary treatment, few patients (n = 3, 13%) performed capillary blood glucose measurements regularly. Symptoms possibly associated with hypoglycemia were present in 13 patients (57%), but CGM revealed periods of low glucose (<4 mmol/l) in all patients, irrespective of the presence of symptoms. GSDIa patients with liver adenomas (n = 9, 41%) showed a higher frequency and area under the curve (AUC) of low blood glucose than patients without adenomas (frequency 2.7 ± 0.8 vs. 1.5 ± 0.7 per day, AUC 0.11 ± 0.08 vs. 0.03 ± 0.02 mmol/l/d; p < 0.05). Similarly, the presence of microalbuminuria was also associated with the frequency of low blood glucose. Z-Scores of bone density correlated negatively with lactate levels.

CONCLUSION

The quality of glucose control is related to the presence of typical long-term complications in GSDI. Many patients experience episodes of asymptomatic low blood glucose. Regular assessment of glucose control is an essential element to evaluate the quality of treatment, and increasing the frequency of glucose self-monitoring remains an important goal of patient education and motivation. CGM devices may support patients to optimize dietary therapy in everyday life.

A preliminary study of telemedicine for patients with hepatic glycogen storage disease and their healthcare providers: from bedside to home site monitoring

BACKGROUND

The purpose of this project was to develop a telemedicine platform that supports home site monitoring and integrates biochemical, physiological, and dietary parameters for individual patients with hepatic glycogen storage disease (GSD).

METHODS AND RESULTS

The GSD communication platform (GCP) was designed with input from software developers, GSD patients, researchers, and healthcare providers. In phase 1, prototyping and software design of the GCP has occurred. The GCP was composed of a GSD App for patients and a GSD clinical dashboard for healthcare providers. In phase 2, the GCP was tested by retrospective patient data entry. The following software functionalities were included (a) dietary registration and prescription module, (b) emergency protocol module, and (c) data import functions for continuous glucose monitor devices and activity wearables. In phase 3, the GSD App was implemented in a pilot study of eight patients with GSD Ia (n = 3), GSD IIIa (n = 1), and GSD IX (n = 4). Usability was measured by the system usability scale (SUS). The mean SUS score was 64/100 [range: 38-93].

CONCLUSIONS

This report describes the design, development, and validation process of a telemedicine platform for patients with hepatic GSD. The GCP can facilitate home site monitoring and data exchange between patients with hepatic GSD and healthcare providers under varying circumstances. In the future, the GCP may support cross-border healthcare, second opinion processes and clinical trials, and could possibly also be adapted for other diseases for which a medical diet is the cornerstone.

Alternative nighttime nutrition regimens in glycogen storage disease type I: a controlled crossover study

BACKGROUND

Traditional approaches for nighttime glycemic control in glycogen storage disease type I (GSDI) include continuous tube feeding, or ingestion of uncooked corn starch (CS) at bedtime. A modified corn starch (MCS) has been shown to prolong euglycemia in some patients. The aim of this study was to evaluate whether stable nighttime glucose control can be achieved with other types of slowly digested carbohydrates in adult GSDI patients.

METHODS

In this cross-over study, nocturnal glucose control and fasting times were assessed with three different nocturnal nutrition regimens in five patients, using continuous glucose monitoring (CGMS) in an outpatient everyday life setting. For each patient, continuous glucose profiles were measured after ingestion of (1) CS, (2) MCS or (3) a pasta meal at bedtime, during 5 to 6 consecutive nights for each regimen.

RESULTS

Stable nocturnal glucose control was achieved for all patients with a pasta meal, with a mean duration of glycemia >3.5 mmol/l of 7.6 h (range 5.7-10.8), and >4 mmol/l of 7 h (5.2-9.2), similar to CS and MCS. Fasting glucose before breakfast on workdays (after 7.1 ± 0.8 h) was not significantly different between the three interventions (CS 4.1 ± 0.5 mmol/l, MCS 4.6 ± 0.7 mmol/l, pasta 4.3 ± 0.9 mmol/l). During prolonged fasting on weekends, longer duration of normoglycemia was achieved with CS or MCS than with pasta.

CONCLUSION

Consumption of cooked pasta is a suitable and more palatable alternative to uncooked corn starch to achieve nighttime glucose control in adult patients with GSDI.

Hepatic glycogen storage disorders: what have we learned in recent years?

PURPOSE OF REVIEW

Glycogen storage disorders (GSDs) are inborn errors of metabolism with abnormal storage or utilization of glycogen. The present review focuses on recent advances in hepatic GSD types I, III and VI/IX, with emphasis on clinical aspects and treatment.

RECENT FINDINGS

Evidence accumulates that poor metabolic control is a risk factor for the development of long-term complications, such as liver adenomas, low bone density/osteoporosis, and kidney disease in GSD I. However, mechanisms leading to these complications remain poorly understood and are being investigated. Molecular causes underlying neutropenia and neutrophil dysfunction in GSD I have been elucidated. Case series provide new insights into the natural course and outcome of GSD types VI and IX. For GSD III, a high protein/fat diet has been reported to improve (cardio)myopathy, but the beneficial effect of this dietary concept on muscle and liver disease manifestations needs to be further established in prospective studies.

SUMMARY

Although further knowledge has been gained regarding pathophysiology, disease course, treatment, and complications of hepatic GSDs, more controlled prospective studies are needed to assess effects of different dietary and medical treatment options on long-term outcome and quality of life.

In vitro digestion of starches in a dynamic gastrointestinal model: an innovative study to optimize dietary management of patients with hepatic glycogen storage diseases

Uncooked cornstarch (UCCS) is a widely used treatment strategy for patients with hepatic glycogen storage disease (GSD). It has been observed that GSD-patients display different metabolic responses to different cornstarches. The objective was to characterize starch fractions and analyze the digestion of different starches in a dynamic gastrointestinal in vitro model. The following brands of UCCS were studied: Argo and Great Value from the United States of America; Brazilian Maizena Duryea and Yoki from Brazil; Dutch Maizena Duryea from the Netherlands. Glycosade, a modified starch, and sweet polvilho, a Brazilian starch extracted from cassava, were also studied. The starch fractions were analyzed by glycemic TNO index method and digestion analyses were determined by the TIM-1 system, a dynamic, computer-controlled, in vitro gastrointestinal model, which simulates the stomach and small intestine. The final digested amounts were between 84 and 86% for the UCCS and Glycosade, but was 75.5% for sweet povilho. At 180 min of the experiment, an important time-point for GSD patients, the digested amount of the starches corresponded to 67.9-71.5 for the UCCS and Glycosade, while it was 55.5% for sweet povilho. In an experiment with a mixture of sweet polvilho and Brazilian Maizena Duryea, a final digested amount of 78.4% was found, while the value at 180 min was 61.7%. Sweet polvilho seems to have a slower and extended release of glucose and looks like an interesting product to be further studied as it might lead to extended normoglycemia in GSD-patients.

Lipids in hepatic glycogen storage diseases: pathophysiology, monitoring of dietary management and future directions

Hepatic glycogen storage diseases (GSD) underscore the intimate relationship between carbohydrate and lipid metabolism. The hyperlipidemias in hepatic GSD reflect perturbed intracellular metabolism, providing biomarkers in blood to monitor dietary management. In different types of GSD, hyperlipidemias are of a different origin. Hypertriglyceridemia is most prominent in GSD type Ia and associated with long-term outcome morbidity, like pancreatitis and hepatic adenomas. In the ketotic subtypes of GSD, hypertriglyceridemia reflects the age-dependent fasting intolerance, secondary lipolysis and increased mitochondrial fatty acid oxidation. The role of high protein diets is established for ketotic types of GSD, but non-traditional dietary interventions (like medium-chain triglycerides and the ketogenic diet) in hepatic GSD are still controversial and necessitate further studies. Patients with these rare inherited disorders of carbohydrate metabolism meet several criteria of the metabolic syndrome, therefore close monitoring for cardiovascular diseases in ageing GSD patients may be justified.

Dietary dilemmas in the management of glycogen storage disease type I

Over the last 50 years, understanding the biochemical bases of glycogen storage disease type I has led to vastly improved survival and health outcomes but the management still centres around an extremely intensive dietary regimen. Patients' metabolic profiles are really determined by the whole of the diet and it can be very difficult to adjust therapy accordingly. In an iso-energetic diet with reference total energy intake, high carbohydrate intake could compromise other macro- and micro-nutrients; if carbohydrates are not restricted then total energy intake is excessive. The quality of the macronutrient such as the glycemic index of carbohydrate, the type of sugar and the proportion of medium-chain triglyceride and essential fatty acids also has a bearing on an individual's long-term metabolic control with potential clinical correlates. These factors as well as the different requirements between individuals and within individuals as they get older mean that the management of glycogen storage disease type I is particularly fraught. Regular clinical and dietary review is imperative as patients grow, ensuring adequate but not excessive low glycaemic index carbohydrate intake, appropriate dynamic biochemical profiles and suitable age appropriate eating patterns. Without diligent management, and education that empowers the patient, these individuals can struggle in adult life.

Improvements of hypertriglyceridemia and hyperlacticemia in Japanese children with glycogen storage disease type Ia by medium-chain triglyceride milk

BACKGROUND

Besides profound hypoglycemia with hyperlacticemia, glycogen storage disease type Ia (GSD Ia) presents hypertriglyceridemia that is often resistant to dietary treatment with cornstarch. The present study aimed to evaluate the effects of medium-chain triglycerides (MCT)--which are absorbed via the portal vein without being incorporated into chylomicrons--on hypertriglyceridemia and to explore otherwise metabolic changes in children with GSD Ia.

PATIENTS AND METHODS

A 13-year-old boy with GSD Ia who received a dietary treatment with MCT milk after cornstarch administration and two infants also with GSD Ia, ages 6 and 7 months, who received MCT milk after carbohydrate-rich, lipid-poor milk were enrolled. In addition to serum glucose and lactate levels, serum levels of total cholesterol, triglycerides, and high-density lipoprotein (HDL) cholesterol were serially determined. Simultaneously, serum levels of total carnitine, free carnitine, acylcarnitine, and ketone bodies were determined to evaluate fatty acid beta-oxidation.

RESULTS

Mean glucose level (mmol/l) of patient 1 remained stable, the value being around 4.5, while those of patients 2 and 3 increased to this level from 4.00 and 3.72, respectively. Lactate levels were significantly decreased in all patients. Mean triglyceride levels (mM) of patient 1 decreased from 3.00 to 2.05. Also, triglyceride levels of patients 2 and 3 decreased from 2.74 and 3.15 to 2.13 and 2.70, respectively. HDL cholesterol, acylcarnitine, and ketone body levels increased in all patients after MCT administration, while total and free carnitine levels decreased.

CONCLUSION

We describe here the beneficial effects on lipid and carbohydrate metabolisms in three Japanese children with GSD Ia. In light of the unfavorable influence of lipid restriction on growth and development in infancy, dietary treatment with MCT milk may be a better treatment for infants with GSD Ia. Further investigation should be required to confirm the efficacy of MCT milk in GSD Ia.

The regulation of growth in glycogen storage disease type 1

OBJECTIVE

To study endocrine and metabolic variables that affect growth in patients with glycogen storage disease type 1 (GSD-1) receiving standard dietary therapy.

DESIGN

Observational study.

PATIENTS AND MEASUREMENTS

Thirty-eight patients with GSD-1, age range 0.6-32.9 years, were investigated on their usual dietary regimens. Data on height, height velocity in prepubertal children, endocrine and metabolic responses to oral glucose load, 24-h serum cortisol and GH concentration profiles and serum IGF-1 concentrations were collected.

RESULTS

The population studied was shorter than average, with a median height standard deviation score (SDS) of -1.60, but significantly taller than a historical population studied at the same institution that had not received dietary therapy at the time of study. A wide range of height SDS was encountered (-5.28 to 1.21) and a subset still exhibit marked growth failure. Median body mass index (BMI) SDS was 0.72 (range -1.34 to 3.96). Those patients with the greatest BMI SDS had the lowest serum GH concentrations but serum IGF-1 concentrations were within the normal range. Patients with the poorest growth exhibit low serum insulin concentration responses to glucose load, GH insensitivity and higher mean 24-h plasma cortisol levels when compared to those patients who were better grown.

CONCLUSION

This study shows that overall the growth of this group of patients with glycogen storage disease type 1 has improved compared to that of a historical control group. There remains a subset of this population with poor growth despite therapy. The measured endocrine responses in this subset are similar to those reported for untreated patients. To improve the growth further in these individuals it will be necessary to understand whether this is failure of prescribed therapy or failure to comply with therapy.

3-methyglutaconic aciduria in a Chinese patient with glycogen storage disease Ib

We report elevated urinary excretion of 3-methylglutaconic (3MGC) and 3-methylglutaric acids (3MGR) in a patient with glycogen storage disease Ib. Combined excretion was 10-fold elevated in comparison to control during inadequate glucose maintenance, and still elevated following dietary improvement. 3MGC acid excretion correlated with plasma lactate and glucose. We speculate that imbalanced gluconeogenesis and de novo cholesterol synthesis result in secondarily increased 3MGC/3MGR production.

Effect of continuous glucose therapy with uncooked cornstarch on the long-term clinical course of type 1a glycogen storage disease

To evaluate the effects of uncooked cornstarch (UCS) on metabolic control, growth, and complications of pubertal and postpubertal subjects with type 1a glycogen storage disease, we studied 26 subjects (16 males), mean age 20.8+/-5.1 years, in whom continuous glucose therapy with cornstarch began at 6.8+/-4.3 years. At the time of this analysis, subjects had received cornstarch for 14.1+/-3.5 years. Metabolic control was determined with subjects receiving their usual home dietary regimens: 4.1+/-1.3 doses of UCS in the day (9.7+/-2.6 g/h) and 2.0+/-0.4 doses at night (11.7+/-2.2 g/h). Mean height standard deviation score (SDS) was -1.2+/-1.3, significantly less than the mean target height of -0.2+/-1.1 ( P<0.01). Mean weight SDS was 0.5+/-1.9 and body mass index SDS was 0.7+/-1.0. Of all subjects, 50% had at least one focal hepatic lesion consistent with an adenoma. Urinary albumin excretion was increased (>20 micro g/min) in 31% of subjects; two subjects had clinical albuminuria (>300 mg per 24 h), but none has progressed to chronic renal insufficiency. Of 26 subjects, 13 (50%) had anemia. All of the complications were associated with evidence of suboptimal metabolic control, whereas subjects with no evidence of any long-term complications had near normal blood lactate and total CO(2) concentrations.

CONCLUSION

The achievement of optimal biochemical control of glycogen storage disease type 1a continues to be a challenge, but is attainable by meticulous adherence to an individualized dietary regimen based on the results of periodic metabolic evaluation and home blood glucose monitoring. Minimizing the metabolic abnormalities of the disease may decrease the risk of long-term complications.

Type I glycogen storage disease: favourable outcome on a strict management regimen avoiding increased lactate production during childhood and adolescence

Our objective was to evaluate the long-term effects of dietary therapy of type I glycogen storage disease which avoids increased lactate production during childhood and adolescence. In order to suppress hepatic glucose and increased lactate production consistently day and night, the treatment regimen included nocturnal intragastric feeding of glucose polymer during childhood and adolescence. The aim was to keep the blood glucose concentration in the "high normal range" (4.3-5.5 mmol/l) and the lactate concentration in urine in the normal range (<0.06 mol/mol creatinine). The amounts of dietary carbohydrate required decreased in an age-related manner from 11.9+/-1.3 mg/kg body weight per min by day and 6.9+/-0.9 mg/kg body weight per min by night at 1 year of age to 5.2+/-1.0 and 2.9+/-1.2 mg/kg body weight per min, respectively, at the age of 16 years. In 15 infants, therapy started at 5.8+/-3.2 months of age and induced catch up growth over 1-2 years by which time the mean height SDS increased from -1.02+/-0.91 to -0.19+/-1.07. In the well controlled patients, further growth continued within that range. From 12 years of age, mean height SDS was in line with the respective mean SDS of mid-parental target height. The plasma lipid concentrations were markedly reduced, but were not brought into the normal range. So far, no adolescent showed liver adenoma or renal damage. Four patients with poor metabolic control due to poor compliance with treatment (frequently subnormal plasma glucose concentrations, severe hypoglycaemia, and increased urinary lactate excretion) showed retardation of growth and bone maturation.

CONCLUSION

avoiding increased lactate production by keeping the blood glucose concentration permanently in the "high normal range" seems to be crucial for growth according to the genetic potential.

Guidelines for management of glycogen storage disease type I - European Study on Glycogen Storage Disease Type I (ESGSD I)

Life-expectancy in glycogen storage disease type I (GSD I) has improved considerably. Its relative rarity implies that no metabolic centre has experience of large series of patients and experience with long-term management and follow-up at each centre is limited. There is wide variation in methods of dietary and pharmacological treatment. Based on the data of the European Study on Glycogen Storage Disease Type I, discussions within this study group, discussions with the participants of the international SHS-symposium 'Glycogen Storage Disease Type I and II: Recent Developments, Management and Outcome' (Fulda, Germany; 22-25th November 2000) and on data from the literature, guidelines are presented concerning: (1). diagnosis, prenatal diagnosis and carrier detection; (2). (biomedical) targets; (3). recommendations for dietary treatment; (4). recommendations for pharmacological treatment; (5). metabolic derangement/intercurrent infections/emergency treatment/preparation elective surgery; and (6). management of complications (directly) related to metabolic disturbances and complications which may develop with ageing and their follow-up.

CONCLUSION

In this paper guidelines for the management of GSD I are presented.

Continuous glucose monitoring in children with glycogen storage disease type I

Glycogen storage disease type I (GSD I) is characterized by impaired production of glucose from glycogenolysis and gluconeogenesis resulting in severe fasting hypoglycaemia. The aim of the present study was to examine the efficacy of a continuous subcutaneous glucose monitoring system (CGMS MiniMed), to determine the magnitude and significance of hypoglycaemia in GSD I and to evaluate the efficacy of its dietary treatment. Four children with GSD I were studied over a 72-h period. Results indicated that the values recorded with continuous subcutaneous glucose monitoring were highly correlated with paired blood glucose values measured by glucometer. Significant periods of asymptomatic hypoglycaemia were noted, especially during night-time. The study suggests that repeated continuous subcutaneous glucose monitoring may serve as a useful tool for the assessment of the long-term management of GSD I patients.

Very low-density lipoprotein apolipoprotein B-100 turnover in glycogen storage disease type Ia (von Gierke disease)

Mixed hyperlipidaemia is a common finding in glycogen storage disease type Ia (GSD Ia). Although cross-sectional studies have demonstrated increases in intermediate-density lipoproteins (IDLs) and reductions in lipoprotein lipase activity, no studies have investigated the dynamics of apolipoprotein B-100 (apo B) metabolism in GSD Ia. This study investigated apoB turnover in GSD Ia using an exogenous labelling method in one sib from a kinship with established GSD Ia. The study demonstrated normal hepatic secretion of very low-density lipoprotein (VLDL), but hypocatabolism of VLDL, probably due to lack of lipoprotein lipase activity. The production rate of IDL was slightly increased, but the turnover rate of low-density lipoprotein was normal. The findings suggest that, as well as a corn starch diet and dietary fat restriction, treatment of severe mixed hyperlipidaemia in GSD Ia and its attendant risk of pancreatitis should possibly involve fibrates that activate lipoprotein lipase and may enhance the clearance of IDL, rather than omega-3 fatty acids, which principally suppress hepatic secretion of VLDL.

Urinary lactate excretion to monitor the efficacy of treatment of type I glycogen storage disease

The purpose of this study was to investigate the usefulness of urinary lactate measurements to assess the adequacy of dietary treatment in patients with type I glycogen storage disease (GSD-I). We determined the correlation of urine and blood lactate concentrations in 21 GSD-I patients during 24-h admissions to the General Clinical Research Center (GCRC) during which hourly blood samples and aliquots of every void were obtained. In all but 1 patient, we found a good correlation between blood lactate concentrations and urinary lactate excretion. One patient did not excrete lactate in significant amounts despite elevated blood lactate concentrations. In 17 patients, the highest blood lactate concentrations occurred during the night. Markedly elevated nighttime average blood lactate concentrations above 3.5 mmol/l resulted in a urinary lactate concentration above the normal limit of 0.067 mmol/mmol creatinine in the first morning urine specimen. Mildly elevated nighttime blood lactate concentrations (between 2.2 and 3.5 mmol/l) led to urinary lactate concentrations that were either normal or moderately elevated. All patients with normal blood lactate concentrations during the night also had normal first morning urinary lactate concentrations. The degree of urinary lactate excretion in relation to blood lactate concentrations varied by individual. Urinary filter paper specimens, collected at home during the night and in the morning and mailed to the laboratory, were used to monitor the dietary compliance of 5 GSD-I patients at home over a period of 6 to 9 weeks prior to their GCRC admissions. These data suggested variable degrees of dietary control. In conclusion, the urinary lactate concentration is a useful parameter to monitor therapy of GSD-I patients at home. To be interpretable, the baseline urinary lactate concentration in relation to the blood lactate concentration has to be determined.

Long-term follow-up of portacaval shunt in glycogen storage disease type 1B

In two girls with glycogen storage disease (GSD) type 1b, terminolateral portacaval shunt (PCS) with partial circular resection of the lobus quadratus of the liver was performed at the age of 12 and 10 years, respectively. At that time, the patients had a height of -3.1 and -1.7 SDS, respectively. PCS resulted in a spectacular growth spurt of 35 cm within the first 5 years after surgery in both of them. As first sign of puberty, breast enlargement started 2.5 years after PCS in both patients. Improved glucose tolerance was evidenced by increased levels of blood glucose and insulin after PCS. Diet with raw cornstarch (CS), 2g/kg body weight four times daily, was started 8 years after PCS in patient 1, but initiated with nightly gastric feeding at the age of 2 years in patient 2, 8 years before PCS. Treatment with recombinant granulocyte colony-stimulating factor (rhGCSF), 6 microg/kg body weight every 36-48 h, was started 20 years after PCS in patient 1, but only 1 month before PCS in patient 2. Progressive development of up to 7-8 liver adenomas was observed after PCS, but without conclusive signs of malignancy on Ferrit MRI. The PCS is still open 23 and 7 years after PCS, respectively. Terminolateral PCS with partial circular resection of the lobus quadratus of the liver associated with dietary control and rhGCSF might still have a place in the treatment of GSD type 1b because it improves the tolerance to fasting and the quality of life and moreover yields excellent metabolic control.

CONCLUSION

Treatment of glycogen storage disease type 1b by portacaval shunt might be considered in patients with height-for-age below the 3rd percentile occurring in spite of dietary control, or before considering liver transplantation which, if necessary, can still be performed after shunt surgery.

Liver transplantation for glycogen storage disease types I, III, and IV

Glycogen storage disease (GSD) types I, III, and IV can be associated with severe liver disease. The possible development of hepatocellular carcinoma and/or hepatic failure make these GSDs potential candidates for liver transplantation. Early diagnosis and initiation of effective dietary therapy have dramatically improved the outcome of GSD type I by reducing the incidence of liver adenoma and renal insufficiency. Nine type I and 3 type III patients have received liver transplants because of poor metabolic control, multiple liver adenomas, or progressive liver failure. Metabolic abnormalities were corrected in all GSD type I and type III patients, while catch-up growth was reported only in two patients. Whether liver transplantation results in reversal and/or prevention of renal disease remains unclear. Neutropenia persisted in both GSDIb patients post liver transplantation necessitating continuous granulocyte colony stimulating factor treatment. Thirteen GSD type IV patients were liver transplanted because of progressive liver cirrhosis and failure. All but one patient have not had neuromuscular or cardiac complications during follow-up periods for as long as 13 years. Four have died within a week and 5 years after transplantation. Caution should be taken in selecting GSD type IV candidates for liver transplantation because of the variable phenotype, which may include life-limiting extrahepatic manifestations. It remains to be evaluated, whether a genotype-phenotype correlation exists for GSD type IV, which may aid in the decision making.

CONCLUSION

Liver transplantation should be considered for patients with glycogen storage disease who have developed liver malignancy or hepatic failure, and for type IV patients with the classical and progressive hepatic form.

Effect of continuous glucose therapy begun in infancy on the long-term clinical course of patients with type I glycogen storage disease

BACKGROUND

To evaluate the effects of continuous glucose therapy on metabolic control, occurrence of severe hypoglycemia, physical growth and development, and complications of glycogen storage disease type I (GSD-I).

METHODS

Seventeen patients (11 males) with GSD-I were studied, mean age 14.6+/-5.0 (SD) years, in whom continuous glucose therapy was begun at 0.8+/-0.4 years. At the time of this study, subjects had received continuous glucose therapy for a total duration of 13.9+/-5.0 years. Uncooked cornstarch was used as the method of providing glucose continuously for 10.2+/-3.2 years. Subjects were admitted to the Clinical Research Center and followed their usual home dietary regimens, which included cornstarch supplements at 2- to 4-hour intervals during the day and at 4- to 8-hour intervals during the night. Plasma glucose, blood lactate, and glucoregulatory hormones were measured hourly for 24 hours.

RESULTS

During a 24-hour period of biochemical monitoring, mean hourly plasma glucose concentrations for the group of 17 subjects ranged from 76+/-17 (SD) mg/dl (4.2+/-0.9 mmol/l) to 108+/-16 mg/dl (6.0+/-0.9 mmol/l), and blood lactate concentrations ranged from 2.1+/-1.2 mmol/l to 3.8+/-2.8 mmol/l. Four subjects had transient plasma glucose levels of 50 mg/dl (2.8 mmol/l) or less in the interval between midnight and 8:00 AM. Mean blood lactate levels were highest (> or =3 mmol/l) between 2:00 and 09:00 AM. Mean height standard deviation score for chronological age (SDS(CA)) was -0.8+/-1.1, significantly (p < 0.01) less than the mean target height SDS of -0.1+/-1.1; mean weight SDS was 0.3+/-1.3. Six (35%) subjects (12.2-21.4 years of age) had anemia with hemoglobin concentrations of 10.6 to 11.6 g/dl. Ultrasound examination showed one or more focal hepatic lesions, consistent with an adenoma in 5 (29%) subjects (10.4 to 21.4 y); 16 subjects had glomerular hyperfiltration; and urinary albumin excretion was increased in 2 subjects, ages 15.9 and 21.1 years.

CONCLUSIONS

Long-term continuous glucose therapy with cornstarch, begun in infancy, resulted in mean height 0.7 SDS less than target height. Optimal biochemical control of GSD-I requires meticulous adherence to an individualized dietary regimen that is based on the results of periodic metabolic evaluation and home blood glucose monitoring. Renal glomerular dysfunction and formation of hepatic adenomata remain serious long-term complications.

[Corn starch in the treatment of patients with glycogenosis type I and III]

RATIONALE

Administering raw corn starch can maintain normoglycemia for long periods after being ingested, thus facilitating control in patients with type I and III glycogenosis.

METHODS

The metabolic effects and the effects on the nutritional status of a treatment with fractionated administrations of raw starch are assessed in two patients with type I glycogenosis (ages 18 and 12 years) and one patient with type III glycogenosis (aged 13 years). In the first two cases the response was previously studied after administering a load of raw corn starch in a water suspension, in an amount similar to the estimated rate of endogenous glucose production during the fasting period (5 mg/kg/minute).

RESULTS

The results of the overload of starch showed a normoglycemia and an absence of lactoacidosis between 4 and 6 hours after its ingestion. The three patients were given two doses of raw corn starch (2 g/kg/dose) at 1.00 and 5.00 hours during the night. After one year of treatment, all patients showed glycemia levels at 9.00 AM that were greater than 90 mg/dl and lactic acid levels that were lower than 2.4 mmol/l. Moreover, in two of the cases there was an increase in the growth rate. In all cases the amount of the hepatomegaly decreased as did the size of the hepatic adenomas that were present in two of the cases.

CONCLUSIONS

In patients with type I and III glycogenosis, raw corn starch can balance the results of the nightly gastric glucose infusion, both with regard to the metabolic control and with regard to the growth.

Metabolic control and renal dysfunction in type I glycogen storage disease

This study was undertaken to determine the effect on renal function of continuous glucose therapy from early childhood. Twenty-three subjects, median age 13.9 years, range 5.9-26.9 years, with type I glycogen storage disease (GSDI) treated with continuous glucose therapy from a median age of 1.3 years, range 0.1-12.9 years, had 24 h monitoring of metabolites and glucoregulatory hormones on their home feeding regimen to assess metabolic control at approximately yearly intervals for a median duration of 8 years. During the most recent evaluation, 24 h urinary albumin excretion rate (AER), kidney size, and creatinine clearance (Ccr) were measured. CCr was unrelated to age and was increased (> 2.33 ml/s per 1.73 m2) in 10/23 (43%). Mean kidney length exceeded 2SD in 16/23 (70%). AER was normal in all five subjects < 10 years and was increased (> 10 micrograms/min) in 8/23 (35%), all > 10 years of age. AER was significantly greater in subject of similar age who started continuous glucose therapy later in childhood and was significantly higher in subjects with lower mean 24 h plasma glucose concentrations and higher mean 24 h blood lactate concentrations, both at the time of assessment of renal function and over the preceding 5 years. GSDI subjects with persistently elevated concentrations of blood lactate, serum lipids and uric acid are at increased risk of nephropathy. Optimal dietary therapy instituted early in life may delay, prevent, or slow the progression of renal disease.

Type Ib glycogenosis

Type Ib glycogenosis is a rare glycogen storage disorder resulting from a defect in the enzyme, glucose-6-phosphatase microsomal translocase. We report a case of Type Ib glycogenosis in an 18 month-old male child who presented with a history of hypoglycemic seizures and recurrent infections and had a massive hepatomegaly, recurrent hypoglycemia, hyperuricemia, hypertriglyceridemia, neutropenia and fasting lactacidemia which decreased sharply on glucose administration.

Three consecutive pregnancies in a patient with glycogen storage disease type IA (von Gierke's disease)

Glycogen storage disease type IA is associated with metabolic abnormalities that can compromise fetal outcome. Normal outcome can be achieved by maintaining euglycemia throughout gestation. We report three consecutive pregnancies in a patient with glycogen storage disease type IA. The patient, a 35-year-old woman, has been maintained on a regimen of nightly nasogastric or cornstarch feedings for the past 12 years with improving metabolic control, reduced liver size, and no progression of multiple hepatic adenomas. On confirmation of each pregnancy, early in the first trimester nightly feeding was changed from cornstarch ingestion to Polycose by nasogastric intubation, with good metabolic control. During the last trimester of each pregnancy metabolic control showed further improvement, with lowering of lactate, urate, and triglyceride levels. During the first pregnancy unexpected fetal death occurred at 33 weeks. During the last two pregnancies, the patient was admitted at 33 and 34 weeks, respectively, for closer supervision of metabolic status and fetal monitoring. She underwent a cesarean section at 35 weeks 4 days of gestation and was delivered of a girl. She underwent a repeat cesarean section at 35 weeks 2 days for the subsequent gestation and was delivered of a boy. Both infants are healthy and appear to be unaffected by von Gierke's disease. Hepatic adenomas did not enlarge during the pregnancies. Meticulous management resulted in normal pregnancy outcomes in two consecutive gestations. Rapid fetal growth late in the third trimester may require particularly careful supervision to maintain euglycemia.

Nutrition therapy for hepatic glycogen storage diseases

Hepatic glycogen storage diseases (GSD) are a group of rare genetic disorders in which glycogen cannot be metabolized to glucose in the liver because of one of a number of possible enzyme deficiencies along the glycogenolytic pathway. Patients with GSD are usually diagnosed in infancy or early childhood with hypoglycemia, hepatomegaly, poor physical growth, and a deranged biochemical profile. Dietary therapies have been devised to use the available alternative metabolic pathways to compensate for disturbed glycogenolysis in GSD I (glucose-6-phosphatase deficiency), GSD III (debrancher enzyme deficiency), GSD VI (phosphorylase deficiency, which is less common), GSD IX (phosphorylase kinase deficiency), and GSD IV (brancher enzyme deficiency). In GSD I, glucose-6-phosphate cannot be dephosphorylated to free glucose. Managing this condition entails overnight continuous gastric high-carbohydrate feedings; frequent daytime feedings with energy distributed as 65% carbohydrate, 10% to 15% protein, and 25% fat; and supplements of uncooked cornstarch. In GSD III, though glycogenolysis is impeded, gluconeogenesis is enhanced to help maintain endogenous glucose production. In contrast to treatment for GSD I, advocated treatment for GSD III comprises frequent high-protein feedings during the day and a high-protein snack at night; energy is distributed as 45% carbohydrate, 25% protein, and 30% fat. Patients with GSD IV, VI, and IX have benefited from high-protein diets similar to that recommended for patients with GSD III.

Type I glycogen storage disease: nine years of management with cornstarch

Long-term effects of cornstarch (CS) therapy on biochemical values and physical growth in children with type I glycogen storage disease (GSD I) were compared to those of children receiving continuous nocturnal nasogastric glucose feedings (CNG). Only patients who had received more than 5 years of dietary therapy (either CS or CNG) were evaluated. Six patients (five female, age 13.5 years +/- 1.3, range 11.7-16.5 years) received CS (1.75-2.5 g/kg, four times daily) and seven patients (five female, age 9.6 +/- 2.5 years, range 7.3-14.8 years) received CNG. Blood glucose, lactate, cholesterol and triglyceride levels were not significantly different between the two methods of treatment. All patients maintained linear growth rates normal for their age. The standard deviation score of height after 6.7 +/- 1.6 years (range 5-9 years) of CS treatment was -1.29 +/- 0.59 and after 8.8 +/- 2.4 years (range 7-14 years) of CNG was -1.24 +/- 0.63. These values did not differ significantly from each other or from the target height, an estimate of genetic potential for height as determined from parental heights. With the exceptions of diarrhea, increased flatulence and excess weight gain, there were no adverse effects of CS after 9 years of treatment. Our data suggests that cornstarch is a simple, effective and safe therapy for GSD I.

Optimal daytime feeding regimen to prevent postprandial hypoglycemia in type 1 glycogen storage disease

To determine the optimal daytime dietary regimen for type 1 glycogen storage disease (GSD), we used uncooked cornstarch (UCS) at a basal glucose production rate (GPR) in single and divided doses, with mixed meals at 0700 and 1700 h. This regimen was compared with a 1.5 times larger single dose of UCS at 0700 h, and with dextrose at GPR at 1200 h. Two-hour UCS loads (amount equal to GPR in 2 h) given with a mixed meal at 0700 h and 180 min later maintained mean blood glucose (BG) concentrations at greater than or equal to 4.2 mmol/L for 300 min. BG was significantly greater from 240 to 300 min compared with a single 4-h UCS load, and at 300 min compared with a single 6-h UCS load. Similar effects were noted when the divided UCS regimen was given with a mixed meal at 1700 h, but not when isoenergetic amounts of dextrose were given on the same schedules with a mixed meal at 1200 h. A daytime schedule of six UCS feedings (with the three main meals and 180 min later) at GPR maintains BG at concentrations that should minimize biochemical abnormalities and optimize clinical outcome in patients with GSD.

Hyperlipidemia and fatty acid composition in patients treated for type IA glycogen storage disease

Because glycogen storage disease type IA (GSD-IA) is characterized by recurrent episodes of hypoglycemia that promote a marked elevation in blood triglyceride levels, we evaluated plasma lipid levels in 12 patients with GSD-IA on a regular basis. Six of the 12 patients had plasma fatty acid composition measured; because of possible essential fatty acid deficiency, urinary prostaglandin excretion was also measured. All patients had triglyceride levels between 1440 and 6120 mg/dl (16.25 to 69.09 mmol/L) before treatment. After treatment to promote blood glucose levels of 75 to 85 mg/dl (4.2 to 4.7 mmol/L), triglyceride levels in each of 11 patients were between 189 +/- 31 (2.13 +/- 0.35 mmol/L) and 510 +/- 60 mg/dl (5.76 +/- 0.68 mmol/L). The lipoprotein fatty acid composition in six patients showed a substantial elevation in C16:0, C16:1 omega 7, and C18:1 omega 9, but no increase in C20:3 omega 9 (the fatty acid that characteristically increases in essential fatty acid deficiency). In addition, each of the six patients had normal 24-hour urinary excretion of prostaglandin. One patient, whose triglyceride levels remained elevated despite dietary treatment, was given either clofibrate, lovastatin, niacin, or fish oil. With the exception of lovastatin, these agents produced a decrease in triglyceride values for 1 to 2 months; however, by 3 months triglycerides reached pretreatment levels. Combined treatment with clofibrate and niacin resulted in a sustained decrease in plasma triglyceride levels for 4 months. The findings indicate that dietary management of GSD-IA is usually associated with improvements in triglyceride levels; however, patients maintain triglyceride values between 300 and 500 mg/dl (3.38 to 5.65 mmol/L). No patient had biochemical evidence of essential fatty acid deficiency.

Continuous glucose for treatment of patients with type 1 glycogen-storage disease: comparison of the effects of dextrose and uncooked cornstarch on biochemical variables

Responses to uncooked cornstarch (UCS), dextrose (Dex), and a 3:1 mixture (UCS:Dex) were determined in seven children with type 1 glycogen-storage disease (GSD-1). UCS maintained blood glucose (BG) and serum insulin concentrations between 3.5 +/- 0.3 and 4.0 +/- 0.4 mmol/L (mean +/- SEM) and 50 +/- 7 and 79 +/- 22 pmol/L, respectively, in six of the seven patients for 4 h. Only four of seven patients completed the 4-h test after UCS:Dex (BG 2.9 +/- 0.3 mmol/L): After Dex, tests had to be stopped in all patients by 150 min after initiation (BG 2.7 +/- 0.4 mmol/L). Two methods of providing dietary glucose overnight, continuous intragastric glucose infusion (COG) and intermittent UCS at 2100 and 0200, were compared by monitoring metabolites and glucoregulatory hormones. The use of UCS in amounts equal to the calculated glucose production rate is an effective method of providing a continuous dietary source of glucose overnight to patients with GSD-1.

Glucose therapy for glycogenosis type 1 in infants: comparison of intermittent uncooked cornstarch and continuous overnight glucose feedings

This study was undertaken to test the glycemic response of five infants with glycogen storage disease type 1, aged 0.7 to 1.5 years, to uncooked cornstarch under various dietary conditions, and to evaluate the long-term effects of a dietary regimen consisting of uncooked cornstarch in milk every 4 hours, in addition to three meals daily, on biochemical values and physical growth. The results were compared with previous experience in treating six infants with continuous overnight glucose infusion via gastrostomy plus multiple daily feedings containing an adequate source of glucose. A test dose of cornstarch (1.6 to 1.8 gm/kg) providing four times the calculated hourly glucose production rate, when given in water 15 to 30 minutes after a continuous overnight intragastric glucose infusion was stopped, did not maintain normoglycemia. When the same dose was given in 2% cow milk 4 hours later, mean blood glucose levels remained greater than 68 mg/dl (3.8 mmol/L) for up to 4 hours. A regimen of uncooked cornstarch in 2% cow milk at 4-hour intervals in addition to three meals daily prevented hypoglycemia, and maintained blood lactate at nearly normal levels and serum uric acid and cholesterol within the normal range; triglyceride levels were increased only modestly. Overnight blood glucose levels were comparable to those achieved with continuous intragastric glucose infusion. With this regimen the five infants have maintained linear growth rates normal for their age and genetic potential; the mean percentage of ideal body weight for length percentile did not change significantly, although two of the five patients were overweight (123% and 124% of ideal body weight respectively) after 3 years of treatment. We conclude that a trial of uncooked cornstarch in feedings of milk every 4 hours should be attempted as soon as a more frequent feeding schedule with dextrose-containing formulas proves ineffective, because the former has the potential to provide the continuous glucose required by infants with glycogen storage disease type 1 in a safer and less invasive fashion than continuous intragastric glucose infusion.

Effects of cornstarch treatment in very young children with type I glycogen storage disease

Three children aged 1-2 years with glycogenosis type I were treated with 2 g/kg bodyweight oral cornstarch per meal (4-5 times a day) for a period up to 16 months. In comparison to the previous dietary regimen (day and nocturnal feedings every 3 h) the cornstarch diet stabilised serum glucose profiles and dramatically improved secondary hyperlipoproteinaemia. Mean total triglycerides decreased up to one half, consistent with a fall of very low density lipoprotein-triglycerides up to two thirds. Metabolic acidosis and hyperuricaemia did not occur and normal growth rates (0.7-1 cm/month) were achieved. We conclude that the cornstarch regimen even in the age group up to 2 years can be considered as an efficient alternative in the treatment of glycogenosis type I patients with less frequent feedings and without nocturnal infusion.

[Carbohydrates in the treatment of glycogenoses]

Glycogen storage diseases (GSD) include inborn errors in glycogen synthesis and degradation which, like most metabolic diseases, evades any therapeutical concept up to now. Nevertheless, in a subgroup of glycogenoses, characterized by functional absence of the key glycogenolytic enzyme glucose-6-phosphatase (GSD-1), dietary treatment is able to ensure almost normal development of affected patients. The principle of treatment consists of oral application of raw cornstarch, which is hydrolyzed slowly in the intestinum resulting in normoglycemia over a period of several hours. Thus, nighttime nasogastric tube-feeding, the standard dietary regimen in GSD-1, could be avoided. Based on our experiences, this therapeutic approach, which has proven successful up to now only in elder children and adults, can be recommended even in children under 2 years of age, if the individual response to an oral starchload has been examined prior to the starch diet.

Glucose production rates in type 1 glycogen storage disease

Glucose production rates were measured in six patients with glycogen storage disease type 1 (five type 1A, one type 1B) using a primed continuous infusion of either [3-3H]glucose or [6,6-2H2]glucose. In four patients exogenous glucose was needed to maintain normoglycaemia. At blood glucose concentrations of 2.3-4.7 mmol/L, the endogenous glucose production rates were between 34 and 100% of that predicted for healthy subjects. No relationship was found between the blood glucose concentration and glucose production rates but there was a positive correlation between that of blood lactate and glucose production rate. The initial steady state was perturbed either by reducing the exogenous glucose infusion rate or by giving intravenous glucagon (20 micrograms/kg) or alanine (0.1-0.2 g/kg). Reducing the exogenous glucose infusion rate had little short term effect on glucose production rate. Intravenous glucagon increased the glucose production rate as well as blood glucose and lactate concentrations. A bolus of alanine (0.2 g/kg) given intravenously increased the glucose production rate and blood glucose concentrations but blood lactate concentrations fell. In four of the patients the studies were repeated under similar conditions and the glucose production rate was higher in all patients. We conclude that the glucose production rate is not fixed but varies with the prevailing metabolic status, a finding that has implications for the treatment of type 1 glycogen storage disease.

Nutritional therapy for selected inborn errors of metabolism

Nutritional approaches are available for the management of several different classes of inborn metabolism errors. In phenylketonuria (PKU), phenylalanine is not properly metabolized; and its accumulation leads to neurologic dysfunction and metal retardation. Altering the diet to limit phenylalanine intake led to remarkable improvement in children with PKU. It was later found that instituting dietary therapy immediately after identification of the disorder in newborns prevented mental retardation. Throughout the 1960s nutritional therapies were found for other inborn disorders, including galactosemia, maple syrup urine disease, and homocystinuria. For the group of disorders associated with defects in the urea cycle, leading to profound hyperammonemia, therapy based on the concept of waste nitrogen excretion (i.e., by increasing excretion of urea cycle intermediates in the urine, nitrogen that would otherwise recycle as ammonia can be eliminated) dramatically produced better control of hyperammonemia and its consequences. Some inborn errors of metabolism respond to vitamin therapy. Biotin-related multiple carboxylase synthetase deficiency can be produced by either of two enzyme defects--holocarboxylase synthetase deficiency or biotinidase deficiency. Both are treatable with biotin supplementation. The symptoms of multiple carboxylase deficiency can also occur after intestinal resection or ingestion of raw eggs. Multiple carboxylase deficiency has been treated successfully in utero by giving the mother biotin supplements. Peroxisomal disorders may respond to dietary management. Liver disease in hereditary tyrosinemia may be accentuated by hypermethioninemia and treated by controlling the blood methionine level. Glycogen storage disease Type I, which causes hypoglycemia, can be controlled by oral administration of cornstarch.

Glycogen storage disease: recommendations for treatment

A workshop was held on "Aspects of treatment of patients with glycogen storage disease" within the framework of the Concerted Action "Inborn errors of metabolism" of the European Communities. Consensus was reached on the main issues of treatment of patients with deficiency of glucose-6-phosphatase, glucose-6-phosphate translocase, debranching enzyme, liver phosphorylase and phosphorylase-b-kinase. The resulting recommendations are reported.

The dietary management of inborn errors of metabolism

Many inborn errors have now been described that can be treated by alterations in diet. Such treatment requires an understanding of both the biochemistry of the defect and of normal nutritional requirements. The principal strategies are cofactor therapy, steps to prevent accumulation of toxic metabolites and the replacement of essential nutrients that are deficient as a result of the metabolic block. It is essential to make sure that any diet used for more than a brief period is complete and capable of sustaining normal growth and development. The treatment of disorders of carbohydrate and amino acid metabolism including organic acidaemias and disorders of the urea cycle and of fat oxidation are discussed.

The dietary treatment of children with type I glycogen storage disease with slow release carbohydrate

The effect of ingestion of uncooked cornstarch (2 g/kg body weight) in water, uncooked starch (1 g/kg) added to a meal, and glucose (2 g/kg) in water, was studied in eight patients with type IA glycogen storage disease (GSD) and one patient with type IB GSD. Blood glucose concentrations were determined at 30-min intervals during each tolerance test; blood lactate, blood insulin, and expiratory hydrogen were determined at 60-min intervals. The glucose levels remained in the normal range (greater than or equal to 1.8 mM) during approximately 6.5-9.0 h, 3.5-6.5 h, and 2.25-4.0 h during the three tolerance tests, respectively. The lactate levels differed markedly for the different tests per patient, and for the same type of test between the patients. Blood insulin concentrations after starch administration did not exceed values of 50 mU/liter above fasting levels and were markedly lower than those after glucose administration (maximum levels of 280 mU/liter). The expiratory hydrogen excretion did not increase or only slightly increased after cornstarch administration (less than 20 ppm).