Thursday, November 15, 2012

Secondary diabetes : Tropical Diabetes, Haemochromatosis, Iatrogenic diabetes

Several diseases and other conditions can cause diabetes or glucose intolerance. Here the defect is not in pancreatic beta cell or in insulin. But other conditions can affect pancreatic functions.

TROPICAL DIABETES

Diabetes present in tropical developing countries. Occur due to fibrosis and calcification of pancreas, called fibrocalcific pancreatic diabetes (FCPD).

ALCOHOL RELATED AND PANCREATIC CAUSES OF DIABETES

Chronic pancreatitis accounts for <1% of all diabetes and chronic alcohol consumption is the usual cause. There is sclerosis of islet cells and thus reduced insulin secretion.
Fig. Haemochromatosis mechanism

HAEMOCHROMATOSIS

Iron storage disease results in liver damage that may progress to cirrhosis and β-cell damage.
Fig. Causes of Secondary diabetes

ENDOCRINE DISORDERS

Polycystic ovary syndrome is common condition associated with obesity, insulin resistance and glucose intolerance or frank type 2 diabetes.

Active thyrotoxicosis or hyperthyroidism on the long run can induce glucose intolerance in about 30-50% of the subjects. Here hepatic glucose production is increased; increased GI motility, insulin clearance is increased, hypersensitivity of beta adrenoreceptors may mediate the elevation of NEFA found in hyperthyroidism.

The hypercortisolemia of Cushing’s syndrome causes increased hepatic gluconeogenesis and hepatic glucose output while skeletal muscle becomes insulin resistant. It also induce lipolysis and protein catabolism, thus reducing glucose clearance (Randal cycle), thus developing glucose intolerance in 80-90% patient and diabetes in 15-20%.

GH in acromegaly can cause glucose intolerance and even diabetes.

Phaeochromocytoma is hypersecretion of adrenal medulla hormones. Adrenaline (epinephrine) has higher hyperglycaemic effect than norepinephrine. Catecholamines stimulate hepatic glycogenolysis and hepatic glucose output, and inhibit insulin secretion via α-receptors; β-receptors induce lipolysis, skeletal muscle glycogenolysis and reduced skeletal muscle glucose uptake. Both receptors augment glucagon secretion.

IATROGENIC DIABETES

Treatment with steroid is the most common form of iatrogenic diabetes. Drugs like thiazides and β-blockers worsen glucose tolerance.

ANTI-INSULIN ANTIBODIES:

Another common form of insulin resistance was due to anti-insulin antibodies in circulation usually occurring by the use of exogenous insulin. 
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