Hypoglycaemia

Question 1

Definition

Answer 1

Low fasting blood glucose, fasting blood glucose <3.3 mmol/L

Question 2

Causes

Answer 2

• In diabetics: insulin therapy & sulfonylureas (e.g. oral Gliclazide, Glibenclamide- stimulate insulin secretion by binding to & closing ATP-dependent K+ channels on beta cell membrane resulting in depolarisation, opening of V-G Ca2+ channels & Ca2+ influx triggering exocytosis of insulin secretory granules)

In non-diabetics: ExPLAIN

Exogenous- alcohol binge on no food, insulin

Pituitary insufficiency- produces GH which increases plasma glucose & ACTH which stimulates cortisol production & cortisol increases plasma glucose (by

Liver failure- IGF-1 stimulated by GH release from anterior pituitary acts in liver

Adrenal insufficiency- adrenal gland doesn’t produce cortisol from zona fasciculata

Islet cell tumours e.g. insulinoma

Non-pancreatic neoplasms e.g. fibrosarcoma

Question 3

Pathophysiology

Answer 3

• Low blood glucose stimulates alpha cells of pancreatic islets to secrete glucagon, which increases hepatic gluconeogenesis & glycogenolysis to increase BG.
• Low BG stimulates release of adrenaline, GH & cortisol (directly stimulates gluconeogenesis; indirectly stimulates glycogenolysis) to increase blood glucose.

Question 4

Signs and symptoms

Answer 4

Autonomic symptoms occur when blood glucose < 3.3.mmol/L due to release of adrenaline & glucagon:

sweating, shaking, hunger, anxiety, nausea

Neuroglycopenic symptoms occur when blood glucose < 2.8 mmol/L due to inadequate glucose supply to brain (brain obligately relies on glucose as an energy source as FFA can’t cross BBB so ketones can’t be used by brain for fuel):

weakness, confusion, vision changes, dizziness

Severe features: convulsions & coma

Question 5

Diagnosis

Answer 5

Whipple’s triad:

• signs & symptoms of hypoglycaemia
• low blood glucose
• resolution of symptoms when blood glucose corrected

Question 6

Treatment

Answer 6

In the community (for example, diabetes mellitus patients who inject insulin):

1st line = Initially give fast-acting carbohydrate- 10-20g oral glucose (tablet/gel/liquid ) then once patient has recovered, give long-acting carbohydrate e.g. slice of toast, 2 biscuits

2nd line = If symptoms don’t resolve: IM glucagon (ineffective in prolonged fasting as liver glycogen stores are depleted) or IV glucose 10%.

• A ‘HypoKit’ may be prescribed which contains a syringe and vial of glucagon for IM or SC injection at home

In the hospital setting:

• If the patient is alert, give quick-acting carbohydrate: 10-20g oral glucose (tablet/gel/liquid)
• If patient is unconscious or can’t swallow, give IM or SC glucagon injection. Alternatively give 10% IV glucose solution.