Pathogenesis of Diabetes mellitus:
The actions of insulin are all anabolic, that is, they promote the lying down of tissue stores
from circulating nutrients. The consequences of insulin deficiency are therefore catabolic,
that is, there is breakdown of tissue energy stores. The major features of diabetes
mellitus are:
• Inability to utilize, and overproduction of, glucose (hyperglycemia)
• Diminished protein synthesis.
• Lipolysis resulting in hyperlipidaemia, hence there is rapid wasting and weight loss.
This state has been aptly described as starvation in the midst of plenty.
In hyperglycaemia the renal threshold for glucose conservation is exceeded, so that there
is osmotic diuresis resulting in polyuria, dehydration and thirst. Lipolysis may also have
serious consequences.
Free fatty acids are converted in the liver to ketone bodies, such as acetoacetate,
acetone and 3-hydroxybutyrate. These dissociate to release hydrogen ions, and a
profound metabolic acidosis may ensue.
The combined result of severe ketosis, acidosis, hyperglycaemia, hyperosmolarity and
electrolyte disturbance is to impair cerebral function, producing diabetic ketoacidotic
coma. This is quite distinct from the hypoglycaemic coma which may also be found in
diabetic patients; this is due to insulin over dosage, and has entirely different clinical
features.
The actions of insulin are all anabolic, that is, they promote the lying down of tissue stores
from circulating nutrients. The consequences of insulin deficiency are therefore catabolic,
that is, there is breakdown of tissue energy stores. The major features of diabetes
mellitus are:
• Inability to utilize, and overproduction of, glucose (hyperglycemia)
• Diminished protein synthesis.
• Lipolysis resulting in hyperlipidaemia, hence there is rapid wasting and weight loss.
This state has been aptly described as starvation in the midst of plenty.
In hyperglycaemia the renal threshold for glucose conservation is exceeded, so that there
is osmotic diuresis resulting in polyuria, dehydration and thirst. Lipolysis may also have
serious consequences.
Free fatty acids are converted in the liver to ketone bodies, such as acetoacetate,
acetone and 3-hydroxybutyrate. These dissociate to release hydrogen ions, and a
profound metabolic acidosis may ensue.
The combined result of severe ketosis, acidosis, hyperglycaemia, hyperosmolarity and
electrolyte disturbance is to impair cerebral function, producing diabetic ketoacidotic
coma. This is quite distinct from the hypoglycaemic coma which may also be found in
diabetic patients; this is due to insulin over dosage, and has entirely different clinical
features.
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Diabetes Mellitus
