Diabetes Mellitus: The Pathophysiology

Deficiency in the production of insulin by the beta cells, delayed or insufficient release of insulin, excessive inactivation of insulin by chemical inhibitors or insensitivity of insulin secretory mechanism of the beta cells lead to a disproportion between blood glucose levels and insulin secretion.
The absence of insulin action leads to impairment in the ability to maintain normal fasting blood glucose bringing about accumulation of glucose in the blood since it cannot enter into muscles and fat cells. The accumulation of glucose raises the blood sugar level (hyperglycaemia)
Excess sugar in the blood suppresses the renal tubular re-absorption mechanism for glucose; the level may rise above 180mg/100ml of blood. This gives way for some of it to be excreted in the urine (glucosuria).
The high molecular weight of glucose ensures that water is pulled along with it as it is excreted, leading to excessive output of urine (polyuria). Uncontrollable loss of excess quantity of water from the body results in excessive thirst and high water intake (polydipsia). Dehydration occurs if the quantity of water the patient takes is not commensurate with the quantity lost through the urine.
The body is starved of energy following the impairment in glucose uptake. The patient feels hungry and eats more in order to meet up the energy requirement of the body. As the cells continue to be deprived of vital energy the body begins to break down its own protein and fat stores leading to loss of weight, and weakness. Continual breakdown of protein and fat leads to an increase in ketone bodies in the blood. If unchecked, this leads to ketoacidosis, hyperventilation, and loss of sodium, chloride, potassium and water.
Large and small vessels in the kidneys, eyes, extremities, heart and brain may be damaged in the long run. The nerves may also be damaged leading to impaired sensitivity in the extremities.
The female diabetic may experience pruritus vulvae (itching of the vulva) as a result of fungal infection which takes advantage of the environment provided by excess glucose deposit from the urine to thrive.
The patient can become prone to injuries on the extremities as a result of impaired sensitivity and eventually develop diabetic ulcers since the wound usually takes a long time to heal because of excess glucose and infection. This may eventually lead to gangrene and amputation. The male patient may also suffer impotence.This is due to changes in the arterial vessels supplying the penile region which makes it difficult to sustain erection.