Zollinger-Ellison Syndrome

Zollinger-Ellison syndrome A rare disorder in which the stomach dramatically increases hydrochloric acid production, resulting in rampant peptic ulcer disease. Zollinger-Ellison syndrome develops as a consequence of benign tumors, called gastrinomas, that secrete the digestive hormone gastrin. Gastrin signals the stomach to produce acid, which the stomach continues doing as long as gastrin remains present. The excess acid that results causes extreme irritation of the gastric mucosa (stomach's lining), leading to numerous ulcers. The gastrinomas may form in the pancreas or the duodenum (first segment of small intestine).

Though gastrinomas are noncancerous, they often spread to other locations (notably the liver) and may develop into cancer over time. Doctors do not know what causes Zollinger-Ellison syndrome though it appears to have a correlation with multiple endocrine neoplasia (men) type 1, a disorder in which tumors (including gastrinomas) develop in numerous endocrine glands.

The symptoms of Zollinger-Ellison syndrome are the same as those for peptic ulcer disease (dyspepsia, nausea, sensation of fullness, possible gastrointestinal bleeding). Endoscopy of the upper

gastrointestinal tract may reveal gastrinomas in the duodenum. Abdominal ULTRASOUND, COMPUTED TOMOGRAPHY (CT) SCAN, or MAGNETIC RESONANCE IMAGING (MRI) can detect gastrinomas in the pancreas or the duodenum. Treatment combines medication to reduce gastric acid production, such as H2 ANTAGONIST (BLOCKER) MEDICATIONS or PROTON PUMP INHIBITOR (PPI) MEDICATIONS, and surgery to remove or reduce the gastrinomas when possible.

See also CANCER RISK FACTORS; CANCER PREVENTION; LIVER CANCER; PANCREATIC CANCER; PANCREATITIS; STOMACH CANCER.

The endocrine glands produce hormones, chemical messengers that regulate many functions within the body. Physician specialists who treat endocrine conditions are endocrinologists and neuroendocrinologists. This section, "The Endocrine System," presents a discussion of the endocrine glands and other structures, the hormones they produce and their functions, an overview of endocrine health and disorders, and entries about the health conditions that involve the endocrine system.

Structures of the Endocrine System

hypothalamus                                   thymus

pituitary gland                                 Islets of Langerhans

anterior pituitary lobe                     adrenal glands posterior pituitary lobe                       adrenal cortex

pineal gland                                          adrenal medulla

thyroid gland                                  ovaries (female)

parathyroid glands                           testicles (male)

Functions of the Endocrine System

The endocrine system and the nervous system work in tandem to direct and regulate the myriad functions of the body, the nervous system through electrical impulses that travel along the nerves and the endocrine system via chemical messengers called hormones. Endocrine glands, sometimes called ductless glands, produce hormones. The endocrine glands release their hormones directly into the bloodstream, and the bloodstream transports them to the cells. Cells throughout the body contain receptors for specific hormones, so even though hormones circulate freely through the blood they affect the functions of only the cells that have receptors for them.

The endocrine glands may be clearly defined or loosely configured structures and are in numerous locations throughout the body. Some collections of endocrine cells inhabit other tissues and organs, such as those in the stomach and small intestine, and in the islets of Langerhans in the pancreas. Other endocrine cells form organized and independent structures, such as the adrenal glands that cap the kidneys and the thyroid gland which

lies across the front of the THROAT. Each endocrine structure produces specific hormones. Collectively the endocrine structures function in intimate synchronization and interaction with each other, continuously adjusting their secretions to accommodate the ever-changing conditions and needs of the body. An intricate matrix of cascades and feedback mechanisms allows this dynamic coordination to initiate and inhibit cellular activity.

THE MAJOR ENDOCRINE STRUCTURES AND THEIR HORMONES

Endocrine Structure

ADRENAL GLANDS

adrenal cortex

adrenal medulla

gastrointestinal tract

HYPOTHALAMUS

Primary Hormones

ALDOSTERONE

CORTISOL

DEHYDROEPIANDROSTERONE (DHEA)

DOPAMINE

EPINEPHRINE

NOREPINEPHRINE

cholecystokinin (CCK)

enterogastrone

gastric inhibitive polypeptide (GPI)

gastrin

motilin

secretin

SOMATOSTATIN

vasoactive intestinal peptide (VIP)

ANTIDIURETIC HORMONE (ADH) CORTICOTROPIN-RELEASING HORMONE

(CRH)

The Endocrine System

Pineal gland Hypothalamus

Pituitary gland

Thyroid gland

Parathyroid glands

Thymus

Adrenal glands

Pancreas

Ovaries

(female)

Testicles (male

Female

Male

Endocrine Structure            Primary Hormones

HYPOTHALAMUS                             dopamine

(continued)                                GONADOTROPIN-RELEASING HORMONE

(GNRH)

GROWTH HORMONE-RELEASING

HORMONE (GHRH) OXYTOCIN

somatostatin

THYROTROPIN-RELEASING HORMONE

(TRH)

ISLETS OF LANGERHANS                GLUCAGON

INSULIN

somatostatin

KIDNEYS                                           ERYTHROPOIETIN (EPO)

RENIN

ovaries                                           ESTROGENS

INHIBIN PROGESTERONE

PARATHYROID GLANDS                 PARATHYROID HORMONE

PINEAL GLAND                                MELATONIN

PITUITARY GLAND anterior pituitary lobe ADRENOCORTICOTROPIN HORMONE (ACTH) FOLLICLE-STIMULATING HORMONE (FSH) GROWTH HORMONE (GH) LUTEINIZING HORMONE (LH) PROLACTIN

THYROID-STIMULATING HORMONE (TSH) posterior pituitary lobe stores and releases as needed: ADH oxytocin

PLACENTA                                     CHORIONIC GONADOTROPIN

estrogen

prolactin

human placental lactogen (hPL)

progesterone

RELAXIN

testes                                inhibin

TESTOSTERONE

THYMUS                                        THYMOSIN

Endocrine Structure            Primary Hormones

THYROID GLAND                            CALCITONIN

THYROXINE (T4) TRIIODOTHYRONINE (T3)

Bridge between control systems: the hypothala-mus The HYPOTHALAMUS is the structural and functional bridge between the BRAIN and the endocrine system. Composed primarily of brain tissue, it receives a constant barrage of NERVE signals from the thalamus, a structure of the brain that serves as a neurologic switchboard for sensory information related to sight, sound, touch, and taste. The physical transition from thalamus to hypothala-mus is difficult to distinguish, highlighting the blurred line between neurologic and endocrine activity that gives rise to the subspecialty of medicine known as neuroendocrinology.

The functions of the hypothalamus primarily relate to survival. Through a combination of nerve impulses and hormonal signals, the hypothalamus regulates BLOOD PRESSURE, HEART RATE, gastrointestinal activity and digestion, body temperature, hunger, and thirst. Hypothalamic hormones target the PITUITARY GLAND, acting either to stimulate or inhibit (stop) the pituitary's secretions. The hypo-thalamus receives hormonal messages directly from the pituitary gland and indirectly through HORMONE levels in the BLOOD, one of a number of feedback mechanisms that helps regulate the hypothalamus's hormonal activity and maintain hormonal balance within the body.

Hormonal choreography: the pituitary gland

Extending downward from the base of the hypo-thalamus, the pituitary gland bulbs out from the end of a short stalk. A dedicated capillary network, the hypophyseoportal circulation, circulates blood between the hypothalamus and the pituitary gland to fast track hormone delivery from the hypothalamus to the pituitary gland. A separate network of blood vessels supplies each structure with blood from the body's circulation to meet the metabolic needs of its cells and to carry pituitary hormones into the body. Communication between the pituitary gland and the hypothala-mus is by necessity intimate and continuous, as the relationship between these two structures regulates basic bodily functions of survival.

The pituitary gland has two structural and functional divisions: the anterior lobe and the posterior lobe. The anterior pituitary lobe directs the activities of the thyroid, parathyroid, adrenal, and sex glands (gonads). The posterior pituitary lobe stores and secretes two hormones it receives from the hypothalamus: ANTIDIURETIC HORMONE (ADH), sometimes called vasopressin, and OXYTOCIN. The release of ADH directs the KIDNEYS to withhold more water, increasing blood volume and thus blood pressure. Oxytocin stimulates contractions of the UTERUS during CHILDBIRTH, and the mother's letdown REFLEX when BREASTFEEDING. Oxytocin also appears to play a role in sexual arousal in both women and men.

Recent research suggests oxytocin interacts with the limbic system, the intersection of neurologic and biochemical response to emotional stress. Levels of oxytocin in the bloodstream rise when stress hormone levels rise, leading researchers to speculate that oxytocin presents a counterbalance to the fight-or-flight response the stress hormones evoke by helping calm the body and restore homeostasis.

Stress management: the adrenal glands The adrenal glands drape across the tops of the kidneys. They produce an array of hormones that increase body functions in response to physiologic stress, such as heart rate and blood pressure. The two portions of the adrenal gland-the cortex (outer portion) and the medulla (inner portion)- have unique functions. The adrenal cortex, rindlike in appearance, secretes steroid hormones that it synthesizes from cholesterol. The primary adrenal cortex hormones are ALDOSTERONE and CORTISOL. Aldosterone regulates the fluid balance in the blood by directing the absorption of water and sodium in the kidneys. This is a fundamental component of a blood pressure-regulation mechanism called the RENIN-angiotensin-aldosterone (RAA) system. Cortisol has numerous effects related to metabolic functions throughout the body. The adrenal cortex also produces small amounts of estrogen, PROGESTERONE, and TESTOSTERONE in men and women alike.

The adrenal medulla, the core of the adrenal gland, secretes EPINEPHRINE, NOREPINEPHRINE (also called adrenaline and noradrenaline), and DOPAMINE. These hormones initiate rapid increases

in heart rate, respiration, and blood pressure, along with changes blood distribution, to allow the body to enter the classic fight-or-flight mode- the stress response. These hormones also provide the "adrenaline rush" that appeals to people who enjoy high-risk activities. Chemically these three substances are catecholamines. In the bloodstream the catecholamines are hormones regulating cell activity. In the interstitial (between-cell) fluid, they function as neurotransmitters, facilitating electrical impulses between nerves. The midbrain, including the hypothalamus, controls the adrenal medulla's secretory activity.

DOPAMINE "TRANSPLANT" FOR PARKINSON'S DISEASE

In the 1980s neurologists experimented with transplanting adrenal medullary tissue into the brains of people who had Parkinson's disease, a progressively degenerative condition that results from depleted dopamine in the brain. Doctors hoped the adrenal medullary tissue would take root in the brain and continue to produce norepi-nephrine, a precursor hormone to dopamine, which other brain chemicals would convert to much-needed dopamine. The risks of the procedure far outweighed the possible benefits, however, and failed to produce consistent results. Doctors today have largely abandoned the method.

Metabolic homeostasis: the thyroid gland

Spread across the throat like an elongated butterfly, the thyroid gland secretes the hormones THY-ROXINE (T4) and TRIIODOTHYRONINE (T3), which direct the rate at which cells consume energy. These hormones regulate numerous body functions, notably heart rate, digestive rate, and thermoregu-lation (body temperature, particularly response to cold). The thyroid's two lobes perform the same functions. The thyroid gland also secretes CALCI-TONIN, which acts to decrease calcium levels in the blood.

Thyroid hormones are essential for life. People who have HYPOTHYROIDISM (underactive thyroid gland) or who have had their thyroid glands destroyed or surgically removed must take lifelong thyroid hormone supplement or replacement therapy. Congenital thyroid deficiency, once called cretinism, in which the thyroid gland is missing or

dysfunctional in the unborn child, results in permanent damage to growth, development, and intellect. Hyperthyroidism, in which the thyroid gland secretes excessive thyroid hormones, can cause serious and permanent damage to the heart and to the eyes (Graves's ophthalmopathy).

Calcium balance: the parathyroid glands Arising from the surface of the thyroid gland where it wraps around the trachea are the four tiny parathyroid glands, arranged in pairs on each of the thyroid gland's two lobes. Though each parathyroid gland alone is barely the size of a grain of rice, the parathyroid glands collectively keep the heart beating, the muscles moving, and the bones solid. The parathyroid glands produce parathyroid hormone, also called parathormone, which regulates the balance between calcium and phosphate. This equilibrium is essential for the conduction of nerve impulses in the heart and the skeletal muscles, proper growth of the bones and teeth in childhood, and bone density and strength in adulthood. The relationship between the thyroid gland and the parathyroid glands is functionally as well as physically intimate. The release of parathyroid hormone causes calcium levels in the blood to rise, counterbalancing the actions of cal-citonin.

Glucose balance: the islets of Langerhans Distributed throughout the exocrine cells that make up the pancreas are about a million clusters of endocrine cells ranging in size from a few dozen to a few hundred cells. These clusters are the islets of Langerhans, and their three distinct cell types secrete the hormones glucagon, insulin, and somatostatin. These hormones regulate the body's balance and use of glucose, the primary source of fuel for many functions of metabolism. The islet cells also secrete a number of other hormones whose functions remain less clearly understood.

Reproduction: the gonads (sex glands) The gonads (sex glands)-the ovaries in women and the testes in men-produce the hormones responsible for sexual maturity and reproductive capability. The gonads become active at puberty, when the hypothalamus signals the pituitary gland to begin producing follicle-stimulating hormone (fsh) and luteinizing hormone (lh). These hormones in turn stimulate the gonads to produce the sex hormones. Men and women alike have all

of these hormones in their bodies; men have a predominance of testosterone and women have a predominance of estrogen and progesterone.

In women the ovaries produce estrogen, progesterone, and a small amount of testosterone. In men the testes produce testosterone, INHIBIN (which regulates SPERM production), and a small amount of estrogen along with a number of other minor hormones that have narrowly specialized functions. In men and women alike, the adrenal cortex produces small amounts of estrogen, progesterone, and testosterone. Estrogen is important for lipid metabolism and storage, testosterone is important for building and maintaining MUSCLE mass, and progesterone is an important precursor hormone for the synthesis of other steroid (lipid-based) hormones.

Building the immune system: the thymus In the 1940s doctors believed there was a connection between an enlarged THYMUS and sudden, unex-plainable death in infants. They termed this condition status thymicolymphaticus and treated it with RADIATION THERAPY to destroy the thymus. There was little evidence to support this connection, however, and doctors began to notice that children treated with irradiation were unusually susceptible to infection. By the 1960s, as understanding began to grow about the functions of the immune system and researchers began to recognize the thymus had a role in immune function, and doctors abandoned both the concept of status thymicolymphaticus and its treatment.

The thymus secretes the hormone THYMOSIN, which helps the immune system's T-cell lymphocytes reach maturity and stimulates blood stem cell production in the BONE MARROW. Researchers speculate the thymus also produces several as yet unidentified hormones that influence immune function. Doctors now know, too, that the normal release of GROWTH HORMONE (GH) during the middle years of childhood stimulates an increase in the size of the thymus, explaining the reason for its enlargement in young children. During this period of development the thymus becomes particularly active in maturing and releasing into the body the T-cells that will form the foundation of immune function for the remainder of life.

Circadian cycles: the pineal gland The PINEAL GLAND, a small pinecone-shaped structure buried

deep in the brain, releases MELATONIN, a hormone associated with sleep cycles. Eastern traditions have long viewed the pineal gland as the metaphysical "third eye," an energy pathway by which the brain communicates directly with the external environment. Western researchers are now discovering this perception may have tangible scientific substance. The pineal gland is located near the optic nerve, which appears to convey input about external light and dark to the pineal gland. Though researchers do not yet fully understand the mechanisms through which this occurs, they do know that melatonin secretion increases with darkness and decreases with lightness, apparently to facilitate the circadian cycle of sleep and wake-fulness. Though as yet melatonin is the only identified hormone the pineal gland produces, researchers believe the pineal gland has additional functions and continue to study its role in the body.

Hormonal rhythms, cascades, and feedback loops The structures of the endocrine system function in tight synchronization with one another. Some hormonal processes are cyclic, under the control of the body's circadian rhythm. Others are "on demand," with physiologic events triggering the release of hormones.

For example, the hypothalamus releases CORTI-COTROPIN-RELEASING HORMONE (CRH) on a regular cycle that begins a sharp spike a few hours before daybreak and peaks a few hours later, dropping off over the daylight hours to trough in the early evening. The release of CRH initiates a cascade of hormonal responses that accelerate metabolism in preparation for the body's heightened level of activity during waking hours: CRH stimulates the pituitary gland to release ADRENOCORTICOTROPIC HORMONE (ACTH), which subsequently stimulates the adrenal cortex to release cortisol. Cortisol then initiates numerous metabolic actions throughout the body.

Correspondingly, hormonal activity from the thyroid gland, islets of Langerhans, and gastrointestinal tract accelerates, instigating further cascades of hypothalamic-pituitary-adrenal activity. As the flow of CRH diminishes, the hormonal cascade slows. Feedback mechanisms also come into play. Cortisol reaches a certain level in the blood circulation, signaling the hypothalamus to stop

releasing CRH. The body's metabolic activity begins to drop off. By nightfall the CRH level reaches its lowest point, and the body is metaboli-cally ready for rest. The pineal gland's release of melatonin similarly follows, and may in fact establish, the body's circadian rhythm.

Other hormonal cycles follow different patterns. The hormonal cascades of puberty, for example, continue during the period of growth during which the secondary sex characteristics emerge-typically a range between the ages of 11 to 12 and 18 to 20. A woman's MENSTRUAL CYCLE repeats approximately every 28 days. The hormones of PREGNANCY follow a precise schedule. Additional hormonal activity occurs in response to physiologic needs in integration with routine hormonal cycles. Feedback loops regulate such activity, with the endocrine system responding to stimuli from other body systems.

During intense physical exercise, for example, the hypothalamus releases ADH in response to hormonal signals from the kidneys (renin release) and barosensory signals from the cardiovascular system, stimulating the adrenal glands to release aldosterone, epinephrine, and norepinephrine to readjust fluid volume, electrolyte balance, heart rate, BREATHING rate, and blood pressure. The various physiologic changes that occur then signal the hypothalamus to stop releasing ADH. Such changes may take the form of rising levels of hormones in the blood or events that indicate the body's needs are being met, such as increased blood volume and elevated blood pressure. Some hormones, such as ADH, are stimulatory; they initiate activity. Other hormones, such as somato-statin, are inhibitory; they stop activity.

Health and Disorders of the Endocrine System

Some endocrine structures are more active early in life, then recede to maintenance roles later in life. The thymus, for example, establishes the foundation of the immune system in early to middle childhood and subsequently shrinks in size and function at puberty to take a background, supportive role in immune function. Other endocrine structures become active at puberty such as the ovaries (female) or testes (male), known collectively as the gonads or sex glands. The sex glands establish the body's SECONDARY SEXual characteristics and reproductive maturity. The functions of the sex glands taper with aging, most prominently in women to define the conclusion of fertility (menopause). Though men can remain fertile throughout their lives, testosterone levels begin to gradually diminish in the mid-30s. Still other endocrine tissues function only under special circumstances, such as the placenta which secretes dozens of hormones that regulate pregnancy.

The most common endocrine disorder in the United States is diabetes (known clinically as diabetes mellitus). Approximately 13 million Americans know they have diabetes, and health experts believe another 5 to 6 million more have diabetes though do not yet know, more than half of whom are over age 60. Diabetes is a significant health influence among adults as the leading cause of heart disease, kidney disease, blindness, and nerve damage (neuropathy). Diabetes accounts directly for more than 70,000 lives lost each year, making it the sixth leading cause of death in the United States. Some people are able to manage their diabetes through lifestyle factors such as diet, exercise, and weight loss and weight management. Others must take medication such as oral antidia-betic medications or insulin injections. Type 1 diabetes is an autoimmune disorder in which the immune system attacks the islets of Langerhans, killing the cells that produce insulin. Type 2 diabetes typically develops in midlife or later, nearly always as a consequence of insulin resistance arising from lifestyle factors. Health experts believe most type 2 diabetes is preventable.

Also common is hypothyroidism (underactive thyroid). About 5 million Americans know they have hypothyroidism. Hypothyroidism affects numerous body functions, including heat regulation, heart rate, blood pressure, body weight, fertility, energy levels, and sleep quality. As with diabetes, health experts believe many more-per-haps another 10 million-have the condition and do not yet know. Hypothyroidism is more common among women and becomes more frequent with advancing age, with some health experts estimating as many as 20 percent of women over age 60 have the condition.

Obesity, in which body weight due to excessive body fat is 20 percent or more greater than healthy

weight, is a complex confluence of endocrine, genetic, and lifestyle factors. Much research focuses on the role of hormones in body functions related to APPETITE (the desire to eat) and metabolism. Research in the 1990s identified two hormones, leptin and ghrelin, that strongly influence appetite. The stomach secretes ghrelin, and adipose (fat) cells throughout the body secrete leptin. The hypothala-mus perceives the changing levels of these hormones in the bloodstream as signals of either hunger or satiety (sense of fullness), and correspondingly accelerates or decelerates digestion and metabolism (use of energy). This research holds intriguing implications, especially for type 2 diabetes. Doctors know that 90 percent of people who have type 2 diabetes also have obesity and estimate that a comparable percentage of people who have obesity also have either insulin resistance or diabetes. Health experts estimate obesity affects 15 percent of American children and 30 percent of American adults.

Traditions in Medical History

For centuries mystery shrouded the very existence of the endocrine glands and their functions. Until human autopsy (cutting open the body after death) became ethically and legally acceptable, doctors learned of endocrine glands or their functions only unintentionally. Physicians knew the signs consistent with the diseases of endocrine dysfunction but lacked the understanding of their causes and thus could not treat them. Historical records dating from ancient Mesopotamia, India, Greece, Rome, and China, for example, document the universal manifestation of diabetes, the first recognized, and even today the most common, endocrine disorder. In diabetes, the islets of Langerhans, collections of endocrine cells in the pancreas, stop secreting insulin, the hormone that "unlocks" cells to allow glucose (sugar), their primary fuel, to enter. As a result, glucose accumulates in the blood while cells literally starve to death.

Antiquarian healers diagnosed diabetes using the same concept modern doctors use (though with vastly different methods), testing the URINE for sugar. Because blood glucose levels rise with inadequate insulin presence, the kidneys attempt to restore the balance by extracting glucose from

the blood and passing it into the urine for excretion from the body. Though the modern method employs laboratory equipment that measures the amount of glucose present in the urine, the ancient physician relied on a far less sophisticated approach: An unfortunate assistant tasted the patient's urine, with sweetness confirming the diagnosis. More innovative or perhaps simply less influential healers had their patients urinate on the ground, then watched to see whether ants swarmed to the site. When ants were attracted to the urine, the diagnosis was "honey urine disease," known today as diabetes.

The diagnosis unfortunately offered little hope for treatment. Ancient healers knew honey urine was a harbinger of death but they did not understand the accountable disease mechanisms. Not until the early 20th century did the scientists Frederick Banting (1891-1941), Charles Best (1899-1978), and John James Rickard Macleod (1876-1935) discover insulin and correlate it to pancreatic function and diabetes. Their research ultimately demonstrated that regular injections of a purified solution prepared with ground pancreatic tissue from pigs or cows, which provided insulin, restored glucose metabolism in people who had diabetes.

The work earned the trio the 1923 Nobel Prize in Physiology or Medicine. More significant, it gave the prospect of normal life to countless people otherwise consigned to near-certain death. And it threw open the door to expanded knowledge of the role of the body's chemical messengers in health and in illness. Modern researchers hope to build on this knowledge to find a cure for diabetes, a disorder that despite treatment remains the leading cause of RENAL FAILURE and blindness and a significant cause of CARDIOVASCULAR DISEASE (CVD).

Breakthrough Research and Treatment Advances

The 20th century saw the field of endocrinology grow from the introduction of the term hormone in 1902 to amazing breakthroughs in understanding of, and treatments for disorders of, endocrine function and neuroendocrine interactions. Researchers now know of nearly 100 hormones the body produces and have developed synthetic hormones to replace or supplement the body's natural hormones as treatments for conditions such as diabetes, hypothyroidism, and osteoporosis. People who have insulin-dependent diabetes now take injections of insulin products genetically engineered in the laboratory to emulate human insulin's precise molecular structure, no longer dependent on purified extracts from animal tissues. Research exploring ISLET CELL TRANSPLANTATION shows promise for being among the therapies that might someday allow doctors to cure diabetes.

Researchers entered other frontiers of endocrine understanding as well. In 1935 scientists finally isolated and named testosterone, the male sex hormone. Shortly after came the discovery of estrogen, the female sex hormone. A quarter century later researchers had turned this knowledge into significant advances on both ends of the fertility spectrum, with the debut of the oral contraceptive (birth control pill) in 1960 and the birth of the first "test tube baby" in 1978. Both discoveries manipulate the hormones responsible for OVULATION, CONCEPTION, and pregnancy. Researchers also have come to recognize that hormones drive most primary cancers of the BREAST, uterus, PROSTATE GLAND, and testicles. New therapies use pharmaceutical interventions (synthetic hormones and chemicals that mimic the structure and action of hormones) to treat or prevent these cancers.

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