The term “diabetes” more often refers to diabetes mellitus (DM). There is, however, another disease also called diabetes, diabetes insipidus (DI). DI is not related to DM, but it can manifest similar symptoms. The fact that DI is far less common than DM accounts for the fact that when the term “diabetes” is unqualified, the usual association is with DM.
Diabetes insipidus results from either a defect in the pituitary gland, which regulates the production of the antidiuretic hormone (ADH), or the kidney’s inability to respond to ADH. The former is referred to as central DI and the latter as nephrogenic DI. ADH is the hormone that regulates the amount of fluid that is retained or passed out of the body.
Diabetes mellitus refers to a group of diseases where the pancreas does not produce enough insulin. Insulin is a hormone that converts sugar, starches, and other food into glucose and other “fuel molecules”. It delivers them to the cells for energy. Its lack or absence causes elevated levels of glucose in the blood stream. This results to a myriad of health problems including cardiovascular diseases; renal failure; damage to the retina, nerves, and blood vessels; and poor healing of wounds. DM is broadly classified into two major types. These are Type 1 diabetes and Type 2 diabetes.
Main Common Symptoms
Diabetes insipidus and diabetes mellitus in all its forms share common characteristic symptoms. These are the trio of polyuria, polydipsia, and polyphagia.
Polyuria
This refers to an increase in urination. On the average, a normal person produces a urine output of about 1.5 liters per day depending on water and food intake and perspiration. A consistent level of 2.5 liters per day is usually deemed excessive. Polyuria is often indicative of underlying pathological conditions that include diabetes, renal abnormalities, cystitis, autoimmune disorders, hyperthyroidism, hypopituitarism, and others; or of biochemical imbalances such as the intake of diuretic drugs, food, and drink or of excessive riboflavin and ascorbic acid.
In a patient with diabetes, polyuria is directly caused by hyperglycemia, or the presence of excessive amounts of glucose or blood sugar in the blood stream. The body’s genitourinary system responds to this condition by attempting to eliminate the excess glucose from the blood through urine. This is filtered from the blood in the kidneys and conveyed to the bladder through the urinary tract. This mode of eliminating the blood sugar leads to frequent urination. This requires additional water, and thus leads to another symptom of diabetes, polydipsia.
In diabetes insipidus, polyuria is caused by a deficient antidiuretic hormone (ADH). This, in turn, is caused by damage to the pituitary gland. ADH induces the kidneys to reabsorb and conserve water for bodily functions limiting urination. The lack of this hormone results to the opposite condition, excessive urination.
Polydipsia
Polydipsia refers to increased or excessive thirst. Thirst is an instinct that induces man to drink. It is normally triggered by a decreased level of fluids in the body. A fluid intake in excess of four liters per day is deemed by medical practitioners to indicate polydipsia. An increased level of liquids decreases osmolality, that is, the concentration of particles in the bloodstream. A level of 50 to 1,400 milliosmoles per kilogram (mOsm/kg) from a clean-catch urine sample is considered normal. While there are normal activities that may lead to excessive thirst, such as intense exercise or the consumption of spicy foods and alcoholic beverages, and medications for various types of illnesses, it could also be symptomatic of a serious illness. Among them is diabetes.
Polydipsia is closely linked with polyuria as the latter depletes the level of liquids in the body. It is for this reason that it (polydipsia) is associated with both diabetes mellitus and diabetes insipidus.
Polyphagia
This means excessive hunger or eating. This condition is also referred to as hyperphagia. The food requirements of each individual may vary according to several factors such as age, size, weight, or usual activity, but medical practitioners generally give a range of 1,200 to 2,400 calories for women and 1,600 to 2,400 calories for men. While a person who exceeds this caloric intake from time to time may not necessarily be afflicted with polyphagia, a continuing desire to eat large quantities of food may be indicative of diabetes.
In Type 1 diabetes, this feeling of hunger is caused by the inability of the beta cells in the islets of Langerhans of the pancreas to produce sufficient insulin. The hormone insulin metabolizes carbohydrates and fats and converts glucose to glycogen, storing it in the liver and muscles. Without insulin glucose cannot be absorbed by the cells. High levels of glucose remain in the blood stream, a condition known as hyperglycemia, instead of providing nutrients for the cells. The cells are starved and this results in hunger and the consequent overeating.
In spite of overeating, a diabetic patient may still suffer weight loss. This is because the inability of the cells to use glycogen for nourishment forces them to use stored fat instead. This depletion of fatty tissues leads to the emaciation of the patient.
This type of diabetes has also been called insulin-dependent diabetes mellitus (IDDM) because its treatment involves the injection of insulin.
In Type 2 diabetes, the beta cells are able to produce sufficient insulin, but the body is unable to use it properly. This condition is called insulin resistance. Insulin resistance has the same effect on the cells as the inability to produce the hormone. It also leads to frequent hunger and overeating and to hyperglycemia. The difference is that in insulin resistance, there is also an elevated level of insulin in the blood. This is known as hyperinsulinemia. This is caused by the continuous production of insulin by the pancreas in response to overeating. The insulin that is present in the blood stream metabolizes the ingested food, but since this is not absorbed by the cells, it is stored as body fat. It is for this reason that a person suffering from Type 2 diabetes could conceivably gain weight, and yet feel fatigued and lethargic. The weight comes from the stored fat, the feeling of lethargy from the starved cells.
Since this type of diabetes does not ordinarily require insulin injections, it has been referred to as non-insulin-dependent diabetes mellitus (NIDDM). However, since current medical research has established that the injection of insulin may be used to manage both types of diabetes depending upon the particular circumstance of the patient, the terms Type 1 and Type 2 are now more frequently used.
Other Symptoms
In addition to the above common symptoms, patients who suffer from Type 1 diabetes also manifest symptoms of chronic nausea and vomiting. Vomiting is a reflex that responds to stimuli from the digestive system, bloodstream, ear, and brain. In patients with diabetes, nausea and vomiting is often due to a paralysis of the muscles of the stomach. This is called gastroparesis and it leads to the improper grinding of food and its abnormal passage into the small intestines. Vomiting usually occurs after meals and since the food is not ground, it comes out in large recognizable pieces. One of the causes of gastroparesis is the damage to the nerves that control stomach muscles due to diabetes mellitus.
Type 1 diabetics may also show symptoms of diabetic ketoacidosis (DKA). This is a metabolic dysfunction characterized by the acetone-smelling breath of the patient and abdominal pain, in addition to polyuria, nausea, and vomiting. If the DKA progresses, this may lead to diabetic coma and may eventually be fatal.
Erectile dysfunction (ED) is attributed to Type 2 diabetes. This is because the disease damages blood vessels, nerves, and certain muscle functions that control erection. While age and other health factors may contribute to the development of ED, it is estimated that men who are afflicted with diabetes experience ED 10 to 15 years earlier than those who are not diabetic.
Amenorrhea or the absence of menstruation results from Type 1 and Type 2 diabetes. Among diabetics, this is often brought about by the weight loss associated with the disease. Sometimes, amenorrhea is also caused by the sheer stress of the abnormal condition of the body.
In both Type 1 and Type 2 diabetes, the patient may show symptoms of blurred vision that could eventually lead to blindness. The lenses of the eyes may change in shape due to glucose absorption. This results in visual changes. While a sustained control of glucose levels may reverse the changes in the lens, failure to implement proper control could result to the more serious ocular damage called diabetic retinopathy. Retinopathy refers to the condition wherein the small blood vessels in the eyes are damaged by excessive levels of glucose. It may be non-proliferative or proliferative. Non-proliferative diabetic retinopathy is a condition wherein blood vessels in the eyes leak fluid into the retina. This causes blurred vision. In its later stages, non-proliferative advances to the proliferative type where new but fragile blood vessels grow in the eye. As these are fragile, they are prone to hemorrhaging and can cause blindness and scarring of the retina.