Diseases Related to Canine Diabetes Mellitus
Certain diseases may contribute to the development of diabetes.
Acromegaly
Acromegaly
is a rare endocrine disease caused by growth hormone excess. It is characterized
by chronic overgrowth of connective tissue, bone and viscera.
Among other clinical signs, insulin resistant diabetes and enlargement
of soft tissue organs and proliferation of gum tissue is seen.
Dogs generally develop acromegaly due to progesterone secretion and growth hormone production by the mammary glands. Acromegaly may rarely be caused by pituitary or hypothalamic neoplasia.
Spaying of bitches is usually curative, although the concurrent diabetes may be permanent, depending on the remaining ability of the pancreas to secrete insulin.
Exocrine pancreatic insufficiency (EPI)
Exocrine pancreatic insufficiency is a congenital or acquired condition that can affect both dogs and cats, although it is more common in dogs. Young adult dogs, especially German Shepherds, are usually affected.
In dogs EPI is usually due to pancreatic acinar atrophy (PAA). It may be seen together with diabetes mellitus if there is damage to both the exocrine and endocrine pancreas.
Pathophysiology
- Digestive enzymes are not secreted normally by the pancreas
- Food is not sufficiently digested and processed
- Diarrhoea and weight loss in spite of a normal or increased appetite
Diagnosis and
treatment
EPI is diagnosed on the basis of blood tests and is treated with
pancreatic enzyme replacements, e.g. Tryplase
(Intervet). Enzyme replacements usually result in improvement
of the clinical signs, and dietary management. However, if due to
chronic pancreatitis and accompanied by diabetes mellitus, it can
be more difficult to treat successfully.
Hyperadrenocorticism (Cushing’s disease)
Hyperadrenocorticism is a relatively common endocrine disease of dogs but is rare in cats.
Aetiology
- Excessive endogenous cortisol production
- pituitary tumour (85% of cases) producing excessive adrenocorticotrophic hormone (ACTH) or
- an adrenal (15% of cases) tumour) producing excessive cortisol
- Iatrogenic administration of exogenous glucocorticoids (iatrogenic hyperadrenocorticism).
Clinical signs
Hyperadrenocorticism is a slowly progressive disease with signs
that vary in severity depending on the duration and degree of cortisol
excess.
Clinical signs are similar to diabetes mellitus:
- polyuria
- polydipsia
- polyphagia
In addition dogs frequently have a pot-bellied appearance and alopecia or other skin and/or coat changes. Diabetes mellitus may develop secondary to hyperadrenocorticism, due to insulin resistance caused by cortisol excess.
Treatment
Hyperadrenocorticism can be treated medically or surgically. Concurrent
diabetes mellitus requires insulin treatment.
Pancreatitis
Pancreatitis is inflammation of the pancreas. Digestive enzymes leak into and damage the surrounding pancreatic tissues.
Aetiology
In most cases the cause of pancreatitis is idiopathic. Other predisposing
factors may be:
- high fat, low protein diet
- other diseases (Cushing's disease, diabetes mellitus)
Risk factors for pancreatitis include:
- breed - Miniature Schnauzer, Miniature poodle and Cocker spaniel are at higher risk
- obesity
- diabetes mellitus
- Cushing's disease
- chronic renal failure
Acute pancreatitis may produce temporary diabetes mellitus and if there is extensive pancreatic necrosis this may become permanent. A similar situation can arise if there is pancreatic neoplasia.