DIABETES MELLITUS

Definition

Diabetes mellitus is a condition in which the pancreas no longer produces enough insulin or cells stop responding to the insulin that is produced, so that glucose in the blood cannot be absorbed into the cells of the body. Symptoms include frequent urination, lethargy, excessive thirst, and hunger.

The treatment includes changes in diet, oral medications, and in some cases, daily injections of insulin.

Description

Diabetes mellitus is a chronic disease that causes serious health complications including renal (kidney) failure, heart disease, stroke, and blindness. Approximately 17 million Americans have diabetes. Unfortunately, as many as one-half are unaware they have it.

Background

Every cell in the human body needs energy in order to function. The body's primary energy source is glucose, a simple sugar resulting from the digestion of foods containing carbohydrates (sugars and starches). Glucose from the digested food circulates in the blood as a ready energy source for any cells that need it. Insulin is a hormone or chemical produced by cells in the pancreas, an organ located behind the stomach. Insulin bonds to a receptor site on the outside of cell and acts like a key to open a doorway into the cell through which glucose can enter. Some of the glucose can be converted to concentrated energy sources like glycogen or fatty acids and saved for later use. When there is not enough insulin produced or when the doorway no longer recognizes the insulin key, glucose stays in the blood rather entering the cells.

The body will attempt to dilute the high level of glucose in the blood, a condition called hyperglycemia, by drawing water out of the cells and into the bloodstream in an effort to dilute the sugar and excrete it in the urine. It is not unusual for people with undiagnosed diabetes to be constantly thirsty, drink large quantities of water, and urinate frequently as their bodies try to get rid of the extra glucose. This creates high levels of glucose in the urine.

At the same time that the body is trying to get rid of glucose from the blood, the cells are starving for glucose and sending signals to the body to eat more food, thus making patients extremely hungry. To provide energy for the starving cells, the body also tries to convert fats and proteins to glucose. The breakdown of fats and proteins for energy causes acid compounds called ketones to form in the blood. Ketones also will be excreted in the urine. As ketones build up in the blood, a condition called ketoacidosis can occur. This condition can be life threatening if left untreated, leading to coma and  death.

Types of diabetes mellitus

Type I diabetes, sometimes called juvenile diabetes, begins most commonly in childhood or adolescence. In this form of diabetes, the body produces little or no insulin. It is characterized by a sudden onset and occurs more frequently in populations descended from Northern European countries (Finland, Scotland, Scandinavia) than in those from Southern European countries, the Middle East, or Asia. In the United States, approximately three people in 1,000 develop Type I diabetes. This form also is called insulin-dependent diabetes because people who develop this type need to have daily injections of insulin.  Brittle diabetics are a subgroup of Type I where patients have frequent and rapid swings of blood sugar levels between hyperglycemia (a condition where there is too much glucose or sugar in the blood) and hypoglycemia (a condition where there are abnormally low levels of glucose or sugar in the blood). These patients may require several injections of different types of insulin during the day to keep the blood sugar level within a fairly normal range.

The more common form of diabetes, Type II, occurs in approximately 3-5% of Americans under 50 years of age, and increases to 10-15% in those over 50. More than 90% of the diabetics in the United States are Type II diabetics. Sometimes called age-onset or adult-onset diabetes, this form of diabetes occurs most often in people who are overweight and who do not exercise. It is also more common in people of Native American, Hispanic, and African-American descent. People who have migrated to Western cultures from East India, Japan, and Australian Aboriginal cultures also are more likely to develop Type II diabetes than those who remain in their original countries. Type II is considered a milder form of diabetes because of its slow onset (sometimes developing over the course of several years) and because it usually can be controlled with diet and oral medication. The consequences of uncontrolled and untreated Type II diabetes, however, are the just as serious as those for Type I. This form is also called noninsulin-dependent diabetes, a term that is somewhat misleading. Many people with Type II diabetes can control the condition with diet and oral medications, however, insulin injections are sometimes necessary if treatment with diet and oral medication is not working.

Another form of diabetes called  gestational diabetes can develop during  pregnancy and generally resolves after the baby is delivered. This diabetic condition develops during the second or third trimester of pregnancy in about 2% of pregnancies. In 2004, incidence of gestational diabetes were reported to have increased 35% in 10 years. Children of women with gestational diabetes are more likely to be born prematurely, have hypoglycemia, or have severe  jaundice at birth. The condition usually is treated by diet, however, insulin injections may be required. These women who have diabetes during pregnancy are at higher risk for developing Type II diabetes within 5-10 years. Diabetes also can develop as a result of pancreatic disease,  alcoholism, malnutrition, or other severe illnesses that  stress the body.

Causes

The causes of diabetes mellitus are unclear, however, there seem to be both hereditary (genetic factors passed on in families) and environmental factors involved. Research has shown that some people who develop diabetes have common genetic markers. In Type I diabetes, the immune system, the body's defense system against infection, is believed to be triggered by a virus or another microorganism that destroys cells in the pancreas that produce insulin. In Type II diabetes, age,< obesity, and family history of diabetes play a role.  In Type II diabetes, the pancreas may produce enough insulin, however, cells have become resistant to the insulin produced and it may not work as effectively. Symptoms of Type II diabetes can begin so gradually that a person may not know that he or she has it. Early signs are lethargy, extreme thirst, and frequent urination. Other symptoms may include sudden weight loss, slow wound healing, urinary tract infections, gum disease, or blurred vision. It is not unusual for Type II diabetes to be detected while a patient is seeing a doctor about another health concern that is actually being caused by the yet undiagnosed diabetes.  Individuals who are at high risk of developing Type II diabetes mellitus include people who:

• are obese (more than 20% above their ideal body weight)
• have a relative with diabetes mellitus
• belong to a high-risk ethnic population (African-American, Native American, Hispanic, or Native Hawaiian)
• have been diagnosed with gestational diabetes or have delivered a baby weighing more than 9 lbs (4 kg)
• have high blood pressure (140/90 mmHg or above)
• have a high density lipoprotein cholesterol level less than or equal to 35 mg/dL and/or a triglyceride level greater than or equal to 250 mg/dL
• have had impaired glucose tolerance or impaired fasting glucose on previous testing  Several common medications can impair the body's use of insulin, causing a condition known as secondary diabetes. These medications include treatments for high blood pressure (furosemide, clonidine, and thiazide diuretics), drugs with hormonal activity ( oral contraceptives, thyroid hormone, progestins, and glucocorticorids), and the anti-inflammation drug indomethacin. Several drugs that are used to treat mood disorders (such as  anxiety and depression) also can impair glucose absorption. These drugs include haloperidol, lithium carbonate, phenothiazines, tricyclic antidepressants, and adrenergic agonists. Other medications that can cause diabetes symptoms include isoniazid, nicotinic acid, cimetidine, and heparin. A 2004 study found that low levels of the essential mineral chromium in the body may be linked to increased risk for diseases associated with insulin resistance.

Symptoms

Symptoms of diabetes can develop suddenly (over days or weeks) in previously healthy children or adolescents, or can develop gradually (over several years) in overweight adults over the age of 40. The classic symptoms include feeling tired and sick, frequent urination, excessive thirst, excessive hunger, and weight loss. Ketoacidosis, a condition due to starvation or uncontrolled diabetes, is common in Type I diabetes. Ketones are acid compounds that form in the blood when the body breaks down fats and proteins. Symptoms include abdominal pain, vomiting, rapid breathing, extreme lethargy, and drowsiness. Patients with ketoacidosis will also have a sweet breath odor. Left untreated, this condition can lead to coma and death.

With Type II diabetes, the condition may not become evident until the patient presents for medical treatment for some other condition. A patient may have heart disease, chronic infections of the gums and urinary tract, blurred vision, numbness in the feet and legs, or slow-healing wounds. Women may experience genital itching.

Diagnosis

Diabetes is suspected based on symptoms. Urine tests and blood tests can be used to confirm a diagnose of diabetes based on the amount of glucose found. Urine can also detect ketones and protein in the urine that may help diagnose diabetes and assess how well the kidneys are functioning. These tests also can be used to monitor the disease once the patient is on a standardized diet, oral medications, or insulin.

ACCESSORY STRUCTURES OF THE SKIN

HAIR

A hair fiber is composed of a tightly fused meshwork of cells filled with the hard protein called keratin. Hair growth is similar to the growth of the epidermal layer of the skin. Deeplying cells in the hair root  produce keratinized cells that move upward through hair follicles (sacs within which each hair fiber grows). Melanocytes (see Figure 16-2) are located at the root of the hair follicle, and they donate the melanin pigment to the cells of the hair fiber. Of the 5 million hairs on the body, about 100,000 are on the head. They grow about ½ inch (1.3 cm) per month. Cutting the hair has no effect on its rate of growth.

NAILS

Nails are hard keratin plates covering the dorsal surface of the last bone of each toe and finger. They are composed of keratinocytes that are cemented together tightly and can extend indefinitely unless cut or broken. A nail grows in thickness and length as a result of division of cells in the region of the nail matrix, which is at the base (proximal portion) of the nail plate. Fingernails grow about 1 mm per week, which means that they can regrow in 3 to 5 months. Toenails grow more slowly than fingernails; it takes 12 to 18 months for toenails to be replaced completely. The lunula is a semilunar (half-moon–shaped) whitish region at the base of the nail plate. It generally can be seen in the thumbnail of most people and is evident to varying degrees in other fingernails. Air mixed in with keratin and cells rich in nuclei give the lunula its whitish color. The cuticle, a narrow band of epidermis (layer of keratin), is at the base and sides of the nail plate. The paronychium is the soft tissue surrounding the nail border. Figure illustrates the anatomic structure of a nail.

Nail growth and appearance commonly alter during systemic disease. For example, grooves in nails may occur with high fevers and serious illness, and spoon nails (flattening of the nail plate) develop in iron deficiency anemia. Onycholysis (onych/o = nail) is the loosening of the nail plate with separation from the nail bed. It may occur with infection of the nail and is often seen in psoriasis.

GLANDS

Sebaceous Glands

Sebaceous glands are located in the dermal layer of the skin over the entire body, with the exception of the palms (hands), soles (feet), and lips. They secrete an oily substance called sebum. Sebum, containing lipids, lubricates the skin and minimizes water loss. Sebaceous glands are closely associated with hair follicles, and their ducts open into the hair follicle through which the sebum is released. Figure shows the relationship of the sebaceous gland to the hair follicle. The sebaceous glands are influenced by sex hormones, which cause them to hypertrophy at puberty and atrophy in old age. Increased production of sebum during puberty contributes to blackhead (comedo) formation and acne in some people.

Sweat Glands

Sweat glands (the most common type are eccrine sweat glands) are tiny, coiled glands found on almost all body surfaces (about 2 million in the body). They are most numerous in the palm of the hand (3000 glands per square inch) and in the sole of the foot. As illustrated in Figure, the coiled eccrine sweat gland originates deep in the dermis and straightens out to extend up through the epidermis. The tiny opening on the surface is a pore. Sweat, or perspiration, is almost pure water, with dissolved materials such as salt making up less than 1% of the total composition. It is colorless and odorless. The odor produced when sweat accumulates on the skin is caused by the action of bacteria on the sweat. Sweat cools the body as it evaporates into the air. Perspiration is controlled by the sympathetic nervous system, whose nerve fibers are activated by the heart regulatory center in the hypothalamic region of the brain, which stimulates sweating.

A special variety of sweat gland, active only from puberty onward and larger than the ordinary kind, is concentrated in a few areas of the body near the reproductive organs and in the armpits. These glands (apocrine sweat glands) secrete an odorless sweat, containing substances easily broken down by bacteria on the skin. The bacterial waste products produce a characteristic human body odor. The milk-producing mammary gland is another type of apocrine gland; it secretes milk after the birth of a child.

THE SKIN

INTRODUCTION

The skin and its accessory structures (hair, nails, and glands) make up the integumentary system of the body. Integument means covering, and the skin (weighing 8 to 10 pounds and extending over an area of 22 square feet in an average adult) is the outer covering for the body. It is, however, more than a simple body covering. This complex system of specialized tissues contains glands that secrete several types of fluids, nerves that carry impulses, and blood vessels that aid in the regulation of the body temperature.

The skin has many important functions:

First, as a protective membrane over the entire body, the skin guards the deeper tissues of the body against excessive loss of water, salts, and heat and against invasion of pathogens and their toxins. Secretions from the skin are slightly acidic in nature, which contributes to the skin’s ability to prevent bacterial invasion. Specialized cells (Langerhans cells) react to the presence of antigens and have an immune function.

Second, the skin contains two types of glands that produce important secretions. These glands in the skin are the sebaceous glands and the sweat glands. Sebaceous glands produce sebum, an oily secretion, and sweat glands produce sweat, a watery secretion. Sebum and sweat pass to the outer edges of the skin through ducts and leave the skin through openings, or pores. Sebum lubricates the surface of the skin, and sweat cools the body as it evaporates from the skin surface.

Third, nerve fibers under the skin are receptors for sensations such as pain, temperature, pressure, and touch. Thus, the body’s adjustment to the environment depends on sensory messages relayed to the brain and spinal cord by sensitive nerve endings in the skin.

Fourth, different tissues in the skin maintain body temperature (thermoregulation).Nerve fibers coordinate thermoregulation by carrying messages to the skin from heat centers in the brain that are sensitive to increases and decreases in body temperature.

Impulses from these fibers cause blood vessels to dilate to bring blood to the surface and

cause sweat glands to produce the watery secretion that carries heat away.

ANATOMY OF THE SKIN

Figure A shows three layers of the skin. Label them from the outer surface inward:

Epidermis [1]—a thin, cellular membrane layer; containing keratin

Dermis [2]—dense, fibrous, connective tissue layer; containing collagen

Subcutaneous layer [3]—thick, fat-containing tissue

EPIDERMIS

The epidermis is the outermost, totally cellular layer of the skin. It is composed of squamous epithelium. Epithelium is the covering of both the internal and the external surfaces of the body. Squamous epithelial cells are flat and scale-like. In the outer layer of the skin, these cells are arranged in several layers (strata) to form stratified squamous epithelium. The epidermis lacks blood vessels, lymphatic vessels, and connective tissue (elastic fibers, cartilage, fat) and is therefore dependent on the deeper dermis layer and its rich network of capillaries for nourishment. In fact, oxygen and nutrients seep out of the capillaries in the dermis, pass through tissue fluid, and supply nourishment to the lower layers of the epidermis.

Figure B illustrates the multilayered cells of the epidermis. The deepest layer is called the basal layer [4]. The cells in the basal layer are constantly growing and multiplying and are the source of all the other cells in the epidermis. As the basal layer cells divide, they are pushed upward and away from the blood supply of the dermal layer by a steady stream of younger cells. In their movement toward the most superficial layer of the epidermis, called the stratum corneum [5], the cells flatten, shrink, lose their nuclei, and die, becoming filled with a hard protein material called keratin. The cells are then called keratinocytes, reflecting their composition of keratin. Finally, within 3 to 4 weeks after beginning as a basal cell in the deepest part of the epidermis, the keratinized cell is sloughed off from the surface of the skin. The epidermis is thus constantly renewing itself, with cells dying at the same rate at which they are replaced. are pushed upward and away from the blood supply of the dermal layer by a steady stream of younger cells. In their movement toward the most superficial layer of the epidermis, called the stratum corneum [5], the cells flatten, shrink, lose their nuclei, and die, becoming filled with a hard protein material called keratin. The cells are then called keratinocytes, reflecting their composition of keratin. Finally, within 3 to 4 weeks after beginning as a basal cell in the deepest part of the epidermis, the keratinized cell is sloughed off from the surface of the skin. The epidermis is thus constantly renewing itself, with cells dying at the same rate at which they are replaced.

The basal layer of the epidermis contains special cells called melanocytes [6]. Melanocytes contain a pigment called melanin that is transferred to other epidermal cells and gives color to the skin. The number of melanocytes in all human races is the same, but the amount of melanin within each cell accounts for the color differences among the races. Individuals with darker skin possess more melanin within the melanocytes, not a greater number of melanocytes. Individuals who are incapable of forming melanin are called albinos. Skin and hair are white. In albinos, eye color varies from red to blue to brown, depending on the amount of melanin present in the iris (pigmented portion of the eye). Occulocutaneous albinism affects eyes, skin, and hair, while ocular albinism affects the eyes only.

Melanin production increases with exposure to strong ultraviolet light, and this creates a suntan, which is a protective response. When the melanin cannot absorb all of the ultraviolet rays, the skin becomes sunburned and inflamed (redness, swelling, and pain).

Over a period of years, excessive exposure to sun tends to cause wrinkles, permanent pigmentary changes, and even cancer of the skin. Because dark-skinned people have more melanin, they acquire fewer wrinkles and they are less likely to develop the types of skin cancer that are associated with ultraviolet light exposure.

DERMIS

The dermis, directly below the epidermis, is composed of blood and lymph vessels and nerve fibers, as well as the accessory organs of the skin, which are the hair follicles, sweat glands, and sebaceous glands. To support the elaborate system of nerves, vessels, and glands, the dermis contains connective tissue cells and fibers that account for the extensibility and elasticity of the skin.

The dermis is composed of interwoven elastic and collagen fibers. Collagen (colla = glue) is a fibrous protein material found in bone, cartilage, tendons, and ligaments, as well as in the skin. It is tough and resistant but also flexible. In the infant, collagen is loose and delicate; it becomes harder as the body ages. During pregnancy, overstretching of the skin with weight gain may break the elastic fibers, resulting in linear markings called striae (“stretch marks”) on the woman’s abdomen and elsewhere. Collagen fibers support and protect the blood and nerve networks that pass through the dermis. Collagen diseases affect connective tissues of the body. Examples of these connective tissue collagen disorders are systemic lupus erythematosus and scleroderma.

SUBCUTANEOUS LAYER

The subcutaneous layer (epidermis and dermis are the cutaneous layers) specializes in the formation of fat. Adipocytes (fat cells) are predominant in the subcutaneous layer, and they manufacture and store large quantities of fat. Obviously, fat deposition varies in different areas of the body and among individual people. Functionally, this layer of the skin is important in protection of the deeper tissues of the body, as a heat insulator, and for energy storage.

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