Paediatric Hypoglycaemia and the Laboratory

AACB Webinar, 8th April 2015 Tina Yen Synopsis

• Definition and classification • Newborn and Neonatal Hypoglycaemia – Transient – Persistant • Hypoglycaemia in infants • Hypoglycaemia in childhood • Essential sample

Definition of hypoglycaemia

• plasma glucose < 2.6 mmol/L • a “practical working definition”

• SYMPTOMS • Note: some infants are asymptomatic with very low blood glucose levels. Others have symptoms of hypoglycaemia at glucose > 2.6 mmol/L and require treatment (but unusual). NEWBORN HYPOGLYCAEMIA 40 mg/dL = 2.2 mmol/L

PEDIATRICS 2011;127:575–579. Clinical Report; Postnatal Glucose Homeostasis in Late-Preterm and Term Infants. AAP 2011 Guidelines on neonatal hypoglycaemia -1 • 1. Routine screening and monitoring of blood glucose not needed in healthy term newborn infants after normal pregnancy and delivery. • 2. Blood glucose concentration only be measured in term infants who have clinical manifestations or who are known to be at risk: – A). Plasma glucose should be measured ASAP (minutes) in symptomatic infant. – B). Glucose monitoring advised if “at risk” • infants who are small for gestational age, • infants who are large for gestational age (>34/40), • infants who were born to mothers who have diabetes • late-preterm infants (LPT 34 – 36(+6)/ 40) AAP 2011 Guidelines on neonatal hypoglycaemia - 2

• 3. Breastfed term infants have lower plasma glucose but higher levels of ketone bodies than formula-fed infants. Breastfed infants may tolerate lower plasma glucose without any clinical manifestations of hypoglycaemia because of high ketones.

PEDIATRICS 2011;127:575–579. Clinical Report; Postnatal Glucose Homeostasis in Late-Preterm and Term Infants. Case-1

• Your lab is called about a baby born at term. Infant is 8h of age and reported to have poor feeding and hypothermia. • Lab plasma glucose was 1.4 mmol/L. • What are the most likely causes ?

Neonatal hypoglycaemia is common

• Hypoglycaemia occurs more commonly during the first days after birth than at any other time of life. • ~ 10% of normal term newborns unable to maintain plasma glucose > 1.7 mmol/L if first feeding is delayed for 3 – 6h after birth. • A transient phenomenon in majority of cases • The significant complexity of the metabolic and endocrine adaptations that occur at birth Paediatric hypoglycaemia by age

NEWBORN NEONATAL INFANT

birth 7 days 2 weeks 1 month 6 months 12 months 5 years

Transient 1. Persistent Idiopathic ketotic hypoglycaemia Hyperinsulinism hypoglycaemia 2. Endocrine disorders 3. Inborn error of metabolism A. Transient (or physiological) hypoglycaemia • Occurs in first 3 days (<72h) after birth prior to establishing feeds • full biochemical screen is not required unless – hypoglycaemia fails to respond to a feed – blood glucose remains persistently or recurrently low. • Neonatal hypoglycaemia may be secondary to septicaemia, severe systemic illness, intrauterine growth retardation or maternal diabetes (ie. NON- PHYSIOLOGICAL)*

* Can have “non-physiological” causes of transient hypoglycaemia Hypoglycaemia in newborns

A Transient B Persistent

• SGA/ LBW • Inborn error of • Preterm metabolism • Stress at delivery • Maternal diabetes • Neonatal illness (infection, hypothermia) C Hypoglycaemia in neonates and infants Transient or persistent?

Peds in Review 1999; 20; e6 – e15. Case-1

• Your lab is called about a baby born at term. Infant is 8h of age and reported to have poor feeding and hypothermia. • Lab plasma glucose was 1.4 mmol/L. • What are the most likely causes ?

IDM - infant of diabetic mother IDM - infant of diabetic mother

• Normal pregnancy – preservation of glucose for the foetus. • If prolonged maternal hyperglycaemia: – foetal hyperglycaemia – foetus produces high levels of insulin and GH (maternal GH and insulin do not cross placenta). Reactive hyperinsulinaemia in foetus – macrosomia • chronic foetal hyperinsulinaemia increases the risk of hypoglycaemia after birth. Newborn may require high concentrations of glucose to maintain euglycaemia. • Neonatal hypoglycaemia due to maternal diabetes should resolve within 7 days. If it does not, the infant should be evaluated for other causes of hypoglycaemia. B. Persistent hypoglycaemia of newborn > 2 days

• May also have hepatomegaly • Neonatal presentation of Inborn Error (IEM) – I. Hepatic enzyme deficiencies • Galactosaemia • Fructosaemia, HFI • Hereditary Tyrosinaemia • Glycogen Storage Disease 1 – II. Mitochondrial fatty acid oxidation and ketogenesis defects C. Hypoglycaemia in neonates and infants

• same as those causing newborn hypoglycaemia • Additional include: – Hyperinsulinism – Endocrine disorders • B. Hypopituitarism • C. Adrenal disorders – Inborn error of metabolism

HYPOGLYCAEMIA OF INFANCY Case-2

• Female aged 7 months presenting with a “bit of gastro” • plasma glucose 0.3 mmol/L • Insulin elevated 61 pmol/L • Cortisol (> 1000 nmol/L) and GH (20.9 nmol/L) (appropriately elevated). • blood glucose and insulin study over 10h - insulin levels were not suppressed by hypoglycaemia. • Dx: PHHI

Persistent hyperinsulinaemic hypoglycaemia of infancy PHHI or “persistent hyperinsulinaemic hypoglycaemia of infancy”

• 1950s described as “idiopathic hypoglycemia of infancy.” • 1960s first insulin RIAs showed that idiopathic hypoglycemia was associated with dysregulation of insulin secretion. • 1970s - problem thought to be islet cell maturation because persistence of ß-cells budding off ductal epithelium. Termed “nesidioblastosis”. • Subsequent investigations showed that nesidioblastosis is a normal feature of the pancreas during the first several months after birth so this term should no longer be used. • 1990s renamed Congenital Hyperinsulinism and thought to be inherited as recessive or dominant traits. Genetic loci associated with HI begin to be defined. Congenital Hyperinsulinism (CH)

• Children with this condition present – during the neonatal period with severe, intractable hypoglycaemia, – later (aged 0 – 3 months) usually at the time of an intercurrent illness. • Plasma insulin concentrations are inappropriately elevated at time of hypoglycaemia. • However insulin levels may not be clearly elevated in CH. Dx requires evidence of excess insulin activity

Criteria for evidence of excess insulin activity

• Suppression of plasma bOHB (hypoketotic) • Suppression of free FA. • Inappropriate glycaemic response (glucose > 1.7 mmol/L) to glucagon Causes of Congenital Hyperinsulinism (CH) • Frequency: rare • ~ 1/30,000 - 50,000 live births. • Five different mutations have been found to cause CH: – sulfonylurea receptor 1 (SUR-1), – Kir6.2, – glucokinase, – Glutamate dehydrogenase (GDH) – mitochondrial enzyme shortchain-3-hydroxyacyl-CoA dehydrogenase (SCHAD) • The most severe forms of CH may require pancreatectomy is the only effective therapeutic option to prevent severe, recurrent hypoglycaemia.

Full list of causes of Congenital Hyperinsulinism

Update on investigating hypoglycaemia in childhood. Tim Lang. Ann Clin Biochem 2011: 1–12. Case-2

• Female aged 7 months presenting with a “bit of gastro” • plasma glucose 0.3 mmol/L • Insulin elevated 61 pmol/L • Cortisol (> 1000 nmol/L) and GH (20.9 nmol/L) (appropriately elevated). • blood glucose and insulin study over 10h - insulin levels were not suppressed by hypoglycaemia. • Dx: PHHI

Persistent hyperinsulinaemic hypoglycaemia of infancy Further Ix

• Transferrin isoform studies - consistent with CDG (Congenital Disorders of Glycosylation type 1) • CDG type 1 defect in synthesis of mannose • persistently elevated insulin that is disproportionate to glucose  prone to hypoglycaemia.

Hypoglycaemia due to endocrine disorders • Addison’s or other adrenal insufficiency – Congenital or acquired bilateral adrenal haemorrhage • Hypopituitarism – GH deficiency +/- ACTH deficiency – Midline facial defect (cleft lip, and palate) – Males may have hypoplastic external genitalia and micropenis.

• Most important laboratory findings – Low plasma GH in presence of hypoglycaemia – short synacthen test showed low basal cortisol and no rise after synacthen • In panhypopituitarism, isolated ACTH deficiency, isolated GH deficiency, or combined ACTH and GH deficiencies, the rate of hypoglycaemia is 20% • In children with CAH, hypoglycaemia is common (prevalence of ~ 8 - 9%). Hypoglycaemia due to inborn errors

GSD 1 final enzyme step for glycogen breakdown and for gluconegenesis Fructose 1,6 block of gluconeogenesis from precursors bisphophatase below pathway level of fructose 1,6 di- def phosphate. Hypoglycaemia if glycogen reserves depleted galactosaemia accumulation of gal-1-phosphate inhibits phosphoglucomutase (hence cannot convert glycogen to glucose) MCAD toxic metabolite accumulation inhibits pyruvate carboxylase (gluconeogenesis). Also faster depletion of glucose due to inability to use ketones as glucose substitute Full list of IEM which present with hypoglycaemia

Update on investigating hypoglycaemia in childhood. Tim Lang. Ann Clin Biochem 2011: 1–12. Fasting study for evaluation of paediatric patient with hypoglycaemia Evaluation of metabolic pathways resulting in hypoglycaemia

• 1. Glycogenolysis • 2. Gluconeogenesis (reverse glycolysis) • 3. Substrates for carbohydrate metabolism • 4. Ketogenesis and Fatty acid oxidation

Glycogen storage disease 1a

• GSD 1a “von Gierke’s disease” • commonest GSD causing hypoglycaemia • Deficiency of glucose-6-phosphatase • The most serious GSD because of complete block in glucose generation from hepatic glycogen stores • PRIMARY Fasting hypoglycaemia • SECONDARY Hyperlactataemia, metabolic acidosis, hyperuricaemia and hyperlipidaemia • Glycogen stores accumulating in the liver leading to marked hepatomegaly. Glucose 6 phosphatase deficiency

• Absence of hepatic G6Pase means glucose unable to leave the hepatocyte phosphorylated  Accumulation of G6P • G6P is metabolized by glycolysis (G6P  pyruvate  lactate). • or G6P is incorporated into glycogen. • Lactate provides the brain with alternative energy source. • Lactate competes with uric acid reducing renal urate clearance  hyperuricemia. Importance of glycogen

• Hepatic glycogen breakdown fundamental role in maintaining blood glucose • Deficiency in G6Pase (GSD 1a and 1b) can present with no measurable blood glucose level. • Tendency to hypoglycaemia - improvement with age due to more efficient utilitisation of gluconeogenic pathways • Note: in GSD 1 (a and b) there is no muscle involvement (muscle does not have G6Pase enzyme). Case 3 (from CHW records)

• 17 year old male • Glycogen storage disease 1a. • Dx at 3.5 months of age • Now has multiple hepatic ademonas, gout, hyperlipidemia, cholelithiasis. • AST 206; ALT 206, GGT 390; Chol 4.9; TG 4.2. • Younger brother Justin also affected (Trig 10.0; Chol 9.2 mmol/L). Case from literature • 3-month-old boy presented to ED • 3-day Hx of poor feeding, reduced urinary output, fever, cough and rhinorrhoea. • Critical hypoglycaemia 0.3 mmol/L • In GSD Ib even profound hypoglycaemia might be clinically unapparent because of the brain’s capability to metabolise ketones and lactate to create energy. • GSD type Ia are genetically deficient in glucose-6- phosphate activity, while those affected with GSD type Ib lack translocase.

Bock DE et al (2010) Acta Pædiatrica 2011 100, pp. e130–e132 Asymptomatic critical hypoglycaemia: a dangerous presentation of glycogen storage disease type Ib in infancy. Abnormality with substrates for carbohydrate metabolism

• All exogenous carbohydrates like fructose, galactose, lactose, sucrose and starch are converted to glucose for generation of energy. • inability to utilise dietary carbohydrate predispose to hypoglycaemia. • Note: Galactosaemia can cause hypoglycaemia

Case 4 (from RCPA)

• 9 day old baby boy • Emergency Department • Term baby, 600 g marked weight loss and jaundice

• Total BR 442 umol/L • Conjugated BR 74 umol/L (0 ‐ 10)

• Additional Information • Random glucose 1.9 mmol/L • (Urine reducing substances +++) Galactosaemia

• Most common form of galactosaemia is deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT) GK • 1. Galactose Gal-1-Phosphate GALT • 2. Gal-1-P UDP Galactose + Glu-1-P epimerase • 3. UDP Galactose UDP Glucose

GK = Galactokinase

Galactosaemia

• Occurs ~ in 60,000 births in Australia (autosomal recessive) • vomiting, hypoglycaemia and liver failure with introduction of lactose-containing milk feeds • Gram negative sepsis • Hepatomegaly. Later cataract occurs. • Can be diagnosed by newborn screening

Galactosaemia

• Normal Lactose metabolism produces: – glucose as immediate supply of energy – galactose which requires conversion into glucose (provides ongoing carbohydrate availability). • Deficiency of galactose-1- phosphate uridyltransferase (GALT) 1:47,000 = Classical Galactosaemia • toxic accumulation of galactose-1-phosphate leads to hepatomegaly, hepatic failure, hypoglycaemia with ketones and predisposition to sepsis particularly Escherichia coli. • Hypoglycaemia is usually only seen once liver impairment has developed. (1) Intestinal lactase

(2) Galactokinase

(3) Galactose-1-phosphate uridyltransferase (GALT)

(4) UDP-galactose-1,4-epimerase (GALE)

HYPOGLYCAEMIA IN CHILDREN Hypoglycaemia in children > 1 year • Ketotic hypoglycaemia – Most common cause of hypoglycaemia in > 12 month old – Occurs between 12 months and 5 years – Develop hypoglycaemia and ketosis when there is carbohydrate restriction • Medications/ Drugs – Intoxication - ETOH – Beta-blockers – Oral hypoglycaemics or insulin Causes continued:

• Secondary hypoglycaemia (acquired causes) – systemic illness, – sepsis, – poor nutritional status (poor diet, malabsorption, coeliac disease). • Malignancy • Insulinoma

Hypoglycemia complicating dehydration due to acute gastroenteritis; Clin Ped 2003; 42: 641 – 646. Essential Diagnostic Sample

• to be collected on child during hypoglycaemic episode • plasma glucose < 2.6 mmol/L • serum for GH, cortisol, insulin, bHB, free FA, lactate, plasma NH3 and acylcarnitines. • Urine ketones and reducing substances (galactose), organic acids (urine metabolic screen), and urine drug screen. Summary

• Definition: plasma glucose < 2.6 mmol/L • “hypoglycaemia” is more common in paediatrics compared to adult medicine. • Acquired causes - systemic illness, sepsis, medications, and poor nutritional status. • Hypopituitarism and adrenal insufficiency should be excluded. • First presentation of an inborn errors of amino acid and organic acid metabolism  urine metabolic screen (organic and amino acids).

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