Hypoglycaemia in the Non-Diabetic Patient Flashcards
What might hepatic glucose output be reduced by?
(General)
Inhibition of hepatic glycogenolysis and gluconeogenesis by insulin
Depletion of hepatic glycogen reserves by malnutrition, fasting, exercise or advanced liver disease
Impaired gluconeogenesis e.g. following alcohol ingestion
What can inhibition of hepatic glycogenolysis and gluconeogenesis by insulin be reversed by?
Injection of glucagon
Will injection of glucagon work in depletion of hepatic glycogen or impaired gluconeogenesis?
In this case insulin levels are already low.
Glucagon will be ineffective.
For example in malnutrition.
What type of symptoms are most common for hypoglycaemia?
Neurological
What are insulinomas?
Pancreatic islet tumours that secrete insulin.
Most of them are sporadic but some patients have multiple tumours arising from neural crest tissue due to multiple endocrine neoplasia.
Are insulomas benign or malignant?
95% are benign
Presenting features of insulinomas.
Recurrent hypoglycaemia often present for months or years before the diagnosis is made.
Diplopia
Sweating, palpitations, weakness
Confusion or abnormal behaviour
Loss of consciousness
Grand mal seizures
What are insulinomas commonly misdiagnosed as?
Psychiatric disorders such as:
Pseudodementia
Epilepsy
Cerebrovascular disease
What is the basis of clinical diagnosis of insulinomas?
Whipple’s triad
What is Whipple’s triad?
Symptoms are associated with fasting or exercise
Hypoglycaemia is confirmed during these episodes
Glucose relieves symptoms
What is a fourth criterion of insulinomas that may be useful?
Inappropriately high insulin levels during hypoglycaemia
How can a diagnosis of an insulinoma be confirmed?
Demonstration of hypoglycaemia in association with inappropriate and excessive insulin secretion.
What tests might be done to diagnose insulinoma?
Measurement of overnight fasting of 16h glucose and insulin levels. This is done on three occassions. It should show up as low glucose and high insulin.
If this is inconclusive a prolonged 72 hour supervised fast can be done.
Suppressive tests such as giving insulin IV and measure C-peptide can be done. Normally exogenous insulin suppresses C-peptide production, but this does not occur in insulinoma.
How can you tell if a patient has overdosed on insulin or whether it is an insulinoma in hypoglycaemia?
Measuring C-peptide or proinsulin.
In an insulinoma they will be high.
Management of insulinomas.
Surgical or medical.
Surgical management of insulinomas.
Excision of the tumour.
Why might surgery of insulinomas be difficult?
They are often very small and difficult to localise.
What techniques can be used to attempt to localise an insulinoma?
Highly selective angiography
Contrast-enhanced high-resolution CT
Scanning with radiolabelled somatostatin (some insulinomas have receptors)
Endoscopic US
Intraoperative US
When is medical treatment of insulinomas indicated?
When the insulinoma is malignant
Tumour cannot be located
Elderly patients with mild symptoms.
What is the medical treatment for insulinomas?
Diazoxide
Somatostatin analogue
Can hypoglycaemia occur with other tumours?
Yes
Explain hypoglycaemia in non-insulinomas.
In advanced neoplasia and cachexia hypoglycaemia might present.
Massive tumours such as sarcomas can produce hypoglycaemia due to secretion of insulin-like growth factor-1.
True ectopic insulin secretion is extremely rare.
Postprandial hypoglycaemia used to be overdiagnosed. Frequent testing after prolonged glucose tolerance test will lead to about 25% of patients showing at least one value below 3 mmol/l. This leads to overdiagnosis.
Give examples of true postprandial hypoglycaemia.
Develop in presence over alcohol.
After gastric surgery (Gastric dumping syndrome)
Explain why postprandial hypoglycaemia might occur in alcohol.
Alcohol primes the cell to produce an excessive amount of insulin.
When a person substitutes lunch for an alcoholic drink instead, this can become a problem.
Explain why postprandial hypoglycaemia might occur after gastric surgery.
Rapid gastric emptying and mismatching of nutrient absorption and insulin secretion.
It is called dumping and is rare nowadays.
Give hepatic and renal causes if hypoglycaemia.
Acute hepatic failure
Terminal renal failure
Why might terminal renal failure cause hypoglycaemia?
Kdiney has a subsidiary role in glucose production via gluconeogenesis in the renal cortex.
Give an example of a hereditary intolerance that can cause hypoglycaemia.
Hereditary fructose intolerance
Endocrine cause of hypoglycaemia.
Addisons
Give drugs that can cause hypoglycaemia
Insulin
Sulphonylureas
Quinine when treating malaria
Salicylates (accidental ingestion in children)
Propranolol (if strenous exercise or starvation)
Pentamidine used to treat resistant Pneumocystis pneumonia.
Explain alcohol-induced hypoglycaemia.
Alcohol inhibits gluconeogenesis.
This means that alcohol can induce hypoglycaemia in poorly nourished chronic alcohol users, binge drinkers and also in children who’s taken a little bit of alcohol.
What do patients with alcohol-induced hypoglycaemia present with?
Coma and hypothermia
What is factitious hypoglycaemia?
Induced by insulin or sulphonylurea.
Can be distingiushed by C-peptide not being proportional to to the levels of insulin.
Sulphonylurea abuse can be detected by chromatography of plasma or urine.
Explain the EXPLAIN mnemonic in hypoglycaemia.
Exogenous drugs?
Pituitary insufficiency?
Liver failure?
Addison’s disease?
Islet cell tumoures?
Non-pancreatic neoplasms?
