A patient with Type 1 diabetes mellitus develops orthostatic hypotension, gastroparesis, and nocturnal diarrhoea. Autonomic testing shows absent heart-rate variability with deep breathing. This constellation is explained by:

• A Diabetic autonomic neuropathy causing dysfunction of both sympathetic (orthostasis) and parasympathetic (heart rate variability, gut motility) systems ✓
• B Adrenal medullary insufficiency due to chronic hyperglycaemia reducing catecholamine synthesis
• C Excessive vagal tone from chronic hyperglycaemia causing bradycardia and gut hypermotility
• D Pontine autonomic failure from diabetic cerebral microangiopathy affecting the dorsal vagal nucleus

Explanation

Diabetic autonomic neuropathy (DAN) affects both limbs of the autonomic nervous system via advanced glycation end-product accumulation and oxidative damage to autonomic nerve fibres. Parasympathetic dysfunction manifests early: reduced heart rate variability with deep breathing (Ewing's test) and resting tachycardia. Sympathetic failure appears later, causing orthostatic hypotension (absent vasoconstriction), gustatory sweating, and erection failure. Gastroparesis (delayed gastric emptying) and diabetic enteropathy (nocturnal diarrhoea) result from vagal and enteric nervous system dysfunction. This is a peripheral postganglionic neuropathy, not a central or adrenal process.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.