Does your child seem much shorter - or much taller - than other kids his or her age? It could be normal. Some children may be small for their age but still be developing normally. Some children are short or tall because their parents are.

But some children have growth disorders. Growth disorders are problems that prevent children from developing normal height, weight, sexual maturity or other features.

Very slow or very fast growth can sometimes signal a gland problem or disease.

The pituitary gland makes growth hormone, which stimulates the growth of bone and other tissues. Children who have too little of it may be very short. Treatment with growth hormone can stimulate growth.

People can also have too much growth hormone. Usually the cause is a pituitary gland tumor, which is not cancer. Too much growth hormone can cause gigantism in children, where their bones and their body grow too much. In adults, it can cause acromegaly, which makes the hands, feet and face larger than normal. Possible treatments include surgery to remove the tumor, medicines, and radiation therapy.

People with dwarfism have short stature. This means that their height is under 4' 10" as an adult. They are usually of normal intelligence. Dwarfism most often does happen in families where both parents are of average height.

More than 300 different conditions can cause dwarfism. Achondroplasia is the most common type of dwarfism. Achondroplasia is a genetic condition that affects about 1 in 15,000 to 1 in 40,000 people. It makes your arms and legs short in comparison to your head and trunk. You may also have a larger head and weak muscle tone. Other genetic conditions, kidney disease, and problems with metabolism or hormones can also cause dwarfism.

The conditions that cause dwarfism can also cause other health problems. Most of them are treatable. It is important to have regular checkups throughout your life. With proper medical care, most people with dwarfism have active lives and live as long as other people.

Dwarfism is a condition that is characterized by short stature, usually resulting in an adult height of 4'10" or shorter. Dwarfism can and most often does occur in families where both parents are of average height. It can be caused by any one of more than 300 conditions, most of which are genetic. The most common type, accounting for 70% of all cases of short stature, is called achondroplasia. Other genetic conditions, kidney disease and problems with metabolism or hormones can also cause short stature. Dwarfism itself is not a disease; however, there is a greater risk of some health problems. With proper medical care, most people with dwarfism have active lives and a normal life expectancy.

A genetic or pathological condition that is characterized by short stature and undersize. Abnormal skeletal growth usually results in an adult who is significantly below the average height.

Your endocrine system includes eight major glands throughout your body. These glands make hormones. Hormones are chemical messengers. They travel through your bloodstream to tissues or organs. Hormones work slowly and affect body processes from head to toe. These include

• Growth and development
• Metabolism - digestion, elimination, breathing, blood circulation and maintaining body temperature
• Sexual function
• Reproduction
• Mood

If your hormone levels are too high or too low, you may have a hormone disorder. Hormone diseases also occur if your body does not respond to hormones the way it is supposed to. Stress, infection and changes in your blood's fluid and electrolyte balance can also influence hormone levels.

In the United States, the most common endocrine disease is diabetes. There are many others. They are usually treated by controlling how much hormone your body makes. Hormone supplements can help if the problem is too little of a hormone.

Both the endocrine and nervous systems use chemical signals to communicate and regulate the body's physiology. The endocrine system releases hormones that act on target cells to regulate development, growth, energy metabolism, reproduction, and many behaviors. The nervous system releases neurotransmitters or neurohormones that regulate neurons, muscle cells, and endocrine cells. Because the neurons can regulate the release of hormones, the nervous and endocrine systems work in a coordinated manner to regulate the body's physiology.

Hypothalamic-Pituitary Axis

The hypothalamus in vertebrates integrates the endocrine and nervous systems. The hypothalamus is an endocrine organ located in the diencephalon of the brain. It receives input from the body and other brain areas and initiates endocrine responses to environmental changes. The hypothalamus acts as an endocrine organ, synthesizing hormones and transporting them along axons to the posterior pituitary gland. It synthesizes and secretes regulatory hormones that control the endocrine cells in the anterior pituitary gland. The hypothalamus contains autonomic centers that control endocrine cells in the adrenal medulla via neuronal control.

The pituitary gland, sometimes called the hypophysis or “master gland” is located at the base of the brain in the sella turcica, a groove of the sphenoid bone of the skull, illustrated in Figure. It is attached to the hypothalamus via a stalk called the pituitary stalk(or infundibulum). The anterior portion of the pituitary gland is regulated by releasing or release-inhibiting hormones produced by the hypothalamus, and the posterior pituitary receives signals via neurosecretory cells to release hormones produced by the hypothalamus. The pituitary has two distinct regions—the anterior pituitary and the posterior pituitary—which between them secrete nine different peptide or protein hormones. The posterior lobe of the pituitary gland contains axons of the hypothalamic neurons.

Anterior Pituitary

The anterior pituitary gland, or adenohypophysis, is surrounded by a capillary network that extends from the hypothalamus, down along the infundibulum, and to the anterior pituitary. This capillary network is a part of the hypophyseal portal system that carries substances from the hypothalamus to the anterior pituitary and hormones from the anterior pituitary into the circulatory system. A portal system carries blood from one capillary network to another; therefore, the hypophyseal portal system allows hormones produced by the hypothalamus to be carried directly to the anterior pituitary without first entering the circulatory system.

The anterior pituitary produces seven hormones: growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TSH), melanin-stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). Anterior pituitary hormones are sometimes referred to as tropic hormones, because they control the functioning of other organs. While these hormones are produced by the anterior pituitary, their production is controlled by regulatory hormones produced by the hypothalamus. These regulatory hormones can be releasing hormones or inhibiting hormones, causing more or less of the anterior pituitary hormones to be secreted. These travel from the hypothalamus through the hypophyseal portal system to the anterior pituitary where they exert their effect. Negative feedback then regulates how much of these regulatory hormones are released and how much anterior pituitary hormone is secreted.

Posterior Pituitary

The posterior pituitary is significantly different in structure from the anterior pituitary. It is a part of the brain, extending down from the hypothalamus, and contains mostly nerve fibers and neuroglial cells, which support axons that extend from the hypothalamus to the posterior pituitary. The posterior pituitary and the infundibulum together are referred to as the neurohypophysis.

The hormones antidiuretic hormone (ADH), also known as vasopressin, and oxytocin are produced by neurons in the hypothalamus and transported within these axons along the infundibulum to the posterior pituitary. They are released into the circulatory system via neural signaling from the hypothalamus. These hormones are considered to be posterior pituitary hormones, even though they are produced by the hypothalamus, because that is where they are released into the circulatory system. The posterior pituitary itself does not produce hormones, but instead stores hormones produced by the hypothalamus and releases them into the blood stream.

Thyroid Gland

The thyroid gland is located in the neck, just below the larynx and in front of the trachea, as shown in Figure. It is a butterfly-shaped gland with two lobes that are connected by the isthmus. It has a dark red color due to its extensive vascular system. When the thyroid swells due to dysfunction, it can be felt under the skin of the neck.

The thyroid gland is made up of many spherical thyroid follicles, which are lined with a simple cuboidal epithelium. These follicles contain a viscous fluid, called colloid, which stores the glycoprotein thyroglobulin, the precursor to the thyroid hormones. The follicles produce hormones that can be stored in the colloid or released into the surrounding capillary network for transport to the rest of the body via the circulatory system.

Thyroid follicle cells synthesize the hormone thyroxine, which is also known as T₄ because it contains four atoms of iodine, and triiodothyronine, also known as T₃ because it contains three atoms of iodine. Follicle cells are stimulated to release stored T₃ and T₄ by thyroid stimulating hormone (TSH), which is produced by the anterior pituitary. These thyroid hormones increase the rates of mitochondrial ATP production.

A third hormone, calcitonin, is produced by parafollicular cells of the thyroid either releasing hormones or inhibiting hormones. Calcitonin release is not controlled by TSH, but instead is released when calcium ion concentrations in the blood rise. Calcitonin functions to help regulate calcium concentrations in body fluids. It acts in the bones to inhibit osteoclast activity and in the kidneys to stimulate excretion of calcium. The combination of these two events lowers body fluid levels of calcium.

Parathyroid Glands

Most people have four parathyroid glands; however, the number can vary from two to six. These glands are located on the posterior surface of the thyroid gland, as shown in Figure. Normally, there is a superior gland and an inferior gland associated with each of the thyroid’s two lobes. Each parathyroid gland is covered by connective tissue and contains many secretory cells that are associated with a capillary network.

The parathyroid glands produce parathyroid hormone (PTH). PTH increases blood calcium concentrations when calcium ion levels fall below normal. PTH (1) enhances reabsorption of Ca²⁺ by the kidneys, (2) stimulates osteoclast activity and inhibits osteoblast activity, and (3) it stimulates synthesis and secretion of calcitriol by the kidneys, which enhances Ca²⁺ absorption by the digestive system. PTH is produced by chief cells of the parathyroid. PTH and calcitonin work in opposition to one another to maintain homeostatic Ca²⁺levels in body fluids. Another type of cells, oxyphil cells, exist in the parathyroid but their function is not known. These hormones encourage bone growth, muscle mass, and blood cell formation in children and women.

Adrenal Glands

The adrenal glands are associated with the kidneys; one gland is located on top of each kidney as illustrated in Figure. The adrenal glands consist of an outer adrenal cortex and an inner adrenal medulla. These regions secrete different hormones.

Adrenal Cortex

The adrenal cortex is made up of layers of epithelial cells and associated capillary networks. These layers form three distinct regions: an outer zona glomerulosa that produces mineralocorticoids, a middle zona fasciculata that produces glucocorticoids, and an inner zona reticularis that produces androgens.

The main mineralocorticoid is aldosterone, which regulates the concentration of Na⁺ ions in urine, sweat, pancreas, and saliva. Aldosterone release from the adrenal cortex is stimulated by a decrease in blood concentrations of sodium ions, blood volume, or blood pressure, or by an increase in blood potassium levels.

The three main glucocorticoids are cortisol, corticosterone, and cortisone. The glucocorticoids stimulate the synthesis of glucose and gluconeogenesis (converting a non-carbohydrate to glucose) by liver cells and they promote the release of fatty acids from adipose tissue. These hormones increase blood glucose levels to maintain levels within a normal range between meals. These hormones are secreted in response to ACTH and levels are regulated by negative feedback.

Androgens are sex hormones that promote masculinity. They are produced in small amounts by the adrenal cortex in both males and females. They do not affect sexual characteristics and may supplement sex hormones released from the gonads.

Adrenal Medulla

The adrenal medulla contains large, irregularly shaped cells that are closely associated with blood vessels. These cells are innervated by preganglionic autonomic nerve fibers from the central nervous system.

The adrenal medulla contains two types of secretory cells: one that produces epinephrine (adrenaline) and another that produces norepinephrine (noradrenaline). Epinephrine is the primary adrenal medulla hormone accounting for 75 to 80 percent of its secretions. Epinephrine and norepinephrine increase heart rate, breathing rate, cardiac muscle contractions, blood pressure, and blood glucose levels. They also accelerate the breakdown of glucose in skeletal muscles and stored fats in adipose tissue.

The release of epinephrine and norepinephrine is stimulated by neural impulses from the sympathetic nervous system. Secretion of these hormones is stimulated by acetylcholine release from preganglionic sympathetic fibers innervating the adrenal medulla. These neural impulses originate from the hypothalamus in response to stress to prepare the body for the fight-or-flight response.

Pancreas

The pancreas, illustrated in Figure, is an elongated organ that is located between the stomach and the proximal portion of the small intestine. It contains both exocrine cells that excrete digestive enzymes and endocrine cells that release hormones. It is sometimes referred to as a heterocrine gland because it has both endocrine and exocrine functions.

The pancreas is found underneath the stomach and points toward the spleen. (credit: modification of work by NCI)

The endocrine cells of the pancreas form clusters called pancreatic islets or the islets of Langerhans, as visible in the micrograph shown in Figure. The pancreatic islets contain two primary cell types: alpha cells, which produce the hormone glucagon, and beta cells, which produce the hormone insulin. These hormones regulate blood glucose levels. As blood glucose levels decline, alpha cells release glucagon to raise the blood glucose levels by increasing rates of glycogen breakdown and glucose release by the liver. When blood glucose levels rise, such as after a meal, beta cells release insulin to lower blood glucose levels by increasing the rate of glucose uptake in most body cells, and by increasing glycogen synthesis in skeletal muscles and the liver. Together, glucagon and insulin regulate blood glucose levels.

Pineal Gland

The pineal gland produces melatonin. The rate of melatonin production is affected by the photoperiod. Collaterals from the visual pathways innervate the pineal gland. During the day photoperiod, little melatonin is produced; however, melatonin production increases during the dark photoperiod (night). In some mammals, melatonin has an inhibitory affect on reproductive functions by decreasing production and maturation of sperm, oocytes, and reproductive organs. Melatonin is an effective antioxidant, protecting the CNS from free radicals such as nitric oxide and hydrogen peroxide. Lastly, melatonin is involved in biological rhythms, particularly circadian rhythms such as the sleep-wake cycle and eating habits.

Gonads

The gonads—the male testes and female ovaries—produce steroid hormones. The testes produce androgens, testosterone being the most prominent, which allow for the development of secondary sex characteristics and the production of sperm cells. The ovaries produce estradiol and progesterone, which cause secondary sex characteristics and prepare the body for childbirth.

Organs with Secondary Endocrine Functions

There are several organs whose primary functions are non-endocrine but that also possess endocrine functions. These include the heart, kidneys, intestines, thymus, gonads, and adipose tissue.

The heart possesses endocrine cells in the walls of the atria that are specialized cardiac muscle cells. These cells release the hormone atrial natriuretic peptide (ANP) in response to increased blood volume. High blood volume causes the cells to be stretched, resulting in hormone release. ANP acts on the kidneys to reduce the reabsorption of Na⁺, causing Na⁺ and water to be excreted in the urine. ANP also reduces the amounts of renin released by the kidneys and aldosterone released by the adrenal cortex, further preventing the retention of water. In this way, ANP causes a reduction in blood volume and blood pressure, and reduces the concentration of Na⁺ in the blood.

The gastrointestinal tract produces several hormones that aid in digestion. The endocrine cells are located in the mucosa of the GI tract throughout the stomach and small intestine. Some of the hormones produced include gastrin, secretin, and cholecystokinin, which are secreted in the presence of food, and some of which act on other organs such as the pancreas, gallbladder, and liver. They trigger the release of gastric juices, which help to break down and digest food in the GI tract.

While the adrenal glands associated with the kidneys are major endocrine glands, the kidneys themselves also possess endocrine function. Renin is released in response to decreased blood volume or pressure and is part of the renin-angiotensin-aldosterone system that leads to the release of aldosterone. Aldosterone then causes the retention of Na⁺ and water, raising blood volume. The kidneys also release calcitriol, which aids in the absorption of Ca²⁺ and phosphate ions. Erythropoietin (EPO) is a protein hormone that triggers the formation of red blood cells in the bone marrow. EPO is released in response to low oxygen levels. Because red blood cells are oxygen carriers, increased production results in greater oxygen delivery throughout the body. EPO has been used by athletes to improve performance, as greater oxygen delivery to muscle cells allows for greater endurance. Because red blood cells increase the viscosity of blood, artificially high levels of EPO can cause severe health risks.

The thymus is found behind the sternum; it is most prominent in infants, becoming smaller in size through adulthood. The thymus produces hormones referred to as thymosins, which contribute to the development of the immune response.

Adipose tissue is a connective tissue found throughout the body. It produces the hormone leptin in response to food intake. Leptin increases the activity of anorexigenic neurons and decreases that of orexigenic neurons, producing a feeling of satiety after eating, thus affecting appetite and reducing the urge for further eating. Leptin is also associated with reproduction. It must be present for GnRH and gonadotropin synthesis to occur. Extremely thin females may enter puberty late; however, if adipose levels increase, more leptin will be produced, improving fertility.

Summary

The pituitary gland is located at the base of the brain and is attached to the hypothalamus by the infundibulum. The anterior pituitary receives products from the hypothalamus by the hypophyseal portal system and produces six hormones. The posterior pituitary is an extension of the brain and releases hormones (antidiuretic hormone and oxytocin) produced by the hypothalamus.

The thyroid gland is located in the neck and is composed of two lobes connected by the isthmus. The thyroid is made up of follicle cells that produce the hormones thyroxine and triiodothyronine. Parafollicular cells of the thyroid produce calcitonin. The parathyroid glands lie on the posterior surface of the thyroid gland and produce parathyroid hormone.

The adrenal glands are located on top of the kidneys and consist of the renal cortex and renal medulla. The adrenal cortex is the outer part of the adrenal gland and produces the corticosteroids, glucocorticoids, and mineralocorticoids. The adrenal medulla is the inner part of the adrenal gland and produces the catecholamines epinephrine and norepinephrine.

The pancreas lies in the abdomen between the stomach and the small intestine. Clusters of endocrine cells in the pancreas form the islets of Langerhans, which are composed of alpha cells that release glucagon and beta cells that release insulin.

Some organs possess endocrine activity as a secondary function but have another primary function. The heart produces the hormone atrial natriuretic peptide, which functions to reduce blood volume, pressure, and Na⁺ concentration. The gastrointestinal tract produces various hormones that aid in digestion. The kidneys produce renin, calcitriol, and erythropoietin. Adipose tissue produces leptin, which promotes satiety signals in the brain.

Hormones are your body's chemical messengers. They travel in your bloodstream to tissues or organs. They work slowly, over time, and affect many different processes, including

• Growth and development
• Metabolism - how your body gets energy from the foods you eat
• Sexual function
• Reproduction
• Mood

Endocrine glands, which are special groups of cells, make hormones. The major endocrine glands are the pituitary, pineal, thymus, thyroid, adrenal glands, and pancreas. In addition, men produce hormones in their testes and women produce them in their ovaries.

Hormones are powerful. It takes only a tiny amount to cause big changes in cells or even your whole body. That is why too much or too little of a certain hormone can be serious. Laboratory tests can measure the hormone levels in your blood, urine, or saliva. Your health care provider may perform these tests if you have symptoms of a hormone disorder. Home pregnancy tests are similar - they test for pregnancy hormones in your urine.

Your pituitary gland is a pea-sized gland at the base of your brain. The pituitary is the "master control gland" - it makes hormones that affect growth and the functions of other glands in the body.

With pituitary disorders, you often have too much or too little of one of your hormones. Injuries can cause pituitary disorders, but the most common cause is a pituitary tumor.

The hypothalamus–pituitary complex can be thought of as the “command center” of the endocrine system. This complex secretes several hormones that directly produce responses in target tissues, as well as hormones that regulate the synthesis and secretion of hormones of other glands. In addition, the hypothalamus–pituitary complex coordinates the messages of the endocrine and nervous systems. In many cases, a stimulus received by the nervous system must pass through the hypothalamus–pituitary complex to be translated into hormones that can initiate a response.

The hypothalamus is a structure of the diencephalon of the brain located anterior and inferior to the thalamus. It has both neural and endocrine functions, producing and secreting many hormones. In addition, the hypothalamus is anatomically and functionally related to the pituitary gland (or hypophysis), a bean-sized organ suspended from it by a stem called the infundibulum (or pituitary stalk). The pituitary gland is cradled within the sellaturcica of the sphenoid bone of the skull. It consists of two lobes that arise from distinct parts of embryonic tissue: the posterior pituitary (neurohypophysis) is neural tissue, whereas the anterior pituitary (also known as the adenohypophysis) is glandular tissue that develops from the primitive digestive tract. The hormones secreted by the posterior and anterior pituitary, and the intermediate zone between the lobes are summarized in image.

Overview

The hypothalamus–pituitary complex is located in the diencephalon of the brain. The hypothalamus and the pituitary gland are connected by a structure called the infundibulum, which contains vasculature and nerve axons. The pituitary gland is divided into two distinct structures with different embryonic origins. The posterior lobe houses the axon terminals of hypothalamic neurons. It stores and releases into the bloodstream two hypothalamic hormones: oxytocin and antidiuretic hormone (ADH). The anterior lobe is connected to the hypothalamus by vasculature in the infundibulum and produces and secretes six hormones. Their secretion is regulated, however, by releasing and inhibiting hormones from the hypothalamus. The six anterior pituitary hormones are: growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL).

Turner syndrome is a genetic disorder that affects a girl's development. The cause is a missing or incomplete X chromosome. Girls who have it are short, and their ovaries don't work properly.

Other physical features typical of Turner syndrome are

• Short, "webbed" neck with folds of skin from tops of shoulders to sides of neck
• Low hairline in the back
• Low-set ears
• Swollen hands and feet

Most women with Turner syndrome are infertile. They are at risk for health difficulties such as high blood pressure, kidney problems, diabetes, cataracts, osteoporosis, and thyroid problems.

Doctors diagnose Turner syndrome based on symptoms and a genetic test. Sometimes it is found in prenatal testing. There is no cure for Turner syndrome, but there are some treatments for the symptoms. Growth hormone often helps girls reach heights that are close to average. Hormone replacement can help start sexual development. Assisted reproduction techniques can help some women with Turner syndrome get pregnant.

Acromegaly is a hormonal disorder that results from the pituitary gland producing too much growth hormone (GH). It is most often diagnosed in middle-aged adults, although symptoms can appear at any age. Signs and symptoms include abnormal growth and swelling of the hands and feet; bone changes that; alter various facial features; arthritis; carpal tunnel syndrome; enlargement of body organs; and various other symptoms. The condition is usually caused by benign tumors on the pituitary called adenomas. Rarely, it is caused by tumors of the pancreas, lungs, and other parts of the brain stimulating the pituitary gland to produce GH. When GH-producing tumors occur in childhood, the disease that results is called gigantism rather than Acromegaly. Acromegaly may also be part of other genetic syndromes such as multiple endocrine neoplasia syndrome type 1 and type 4, hereditary paraganglioma-pheochromocytoma syndrome, McCune-Allright syndrome, neurofibromatosis or Carney complex.

Acromegaly is a disorder that occurs when your body makes too much growth hormone (GH). Produced mainly in the pituitary gland, GH controls the physical growth of the body. In adults, too much of this hormone causes bones, cartilage, body organs, and other tissues to increase in size. Common changes in appearance include enlarged or swollen nose, ears, hands, and feet.

Acromegaly is rare. Scientists estimate that about 3 to 14 of every 100,000 people have been diagnosed as having acromegaly.

Beckwith-Wiedemann syndrome is a condition that affects many parts of the body. It is classified as an overgrowth syndrome, which means that affected infants are larger than normal (macrosomia), and some may be taller than their peers during childhood. Growth begins to slow by about age 8, and adults with this condition are not unusually tall. In some children with Beckwith-Wiedemann syndrome, specific body parts may grow abnormally large on one side of the body, leading to an asymmetric or uneven appearance. This unusual growth pattern, which is known as hemihyperplasia, usually becomes less apparent over time.

The signs and symptoms of Beckwith-Wiedemann syndrome vary among affected individuals. Some children with this condition are born with an opening in the wall of the abdomen (an omphalocele) that allows the abdominal organs to protrude through the belly-button. Other abdominal wall defects, such as a soft out-pouching around the belly-button (an umbilical hernia), are also common. Some infants with Beckwith-Wiedemann syndrome have an abnormally large tongue (macroglossia), which may interfere with breathing, swallowing, and speaking. Other major features of this condition include abnormally large abdominal organs (visceromegaly), creases or pits in the skin near the ears, low blood glucose (hypoglycemia) in infancy, and kidney abnormalities.

Children with Beckwith-Wiedemann syndrome are at an increased risk of developing several types of cancerous and noncancerous tumors, particularly a form of kidney cancer called Wilms tumor and a form of liver cancer called hepatoblastoma. Tumors develop in about 10 percent of people with this condition and almost always appear in childhood.

Most children and adults with Beckwith-Wiedemann syndrome do not have serious medical problems associated with the condition. Their life expectancy is usually normal.

Growth charts consist of a series of percentile curves that illustrate the distribution of selected body measurements in children. Pediatric growth charts have been used by pediatricians, nurses, and parents to track the growth of infants, children, and adolescents in the United States since 1977.

CDC recommends that health care providers:

• Use the WHO growth standards to monitor growth for infants and children ages 0 to 2 years of age in the U.S.
• Use the CDC growth charts for children age 2 years and older in the U.S.

Growth charts are not intended to be used as a sole diagnostic instrument. Instead, growth charts are tools that contribute to forming an overall clinical impression for the child being measured.

McCune-Albright syndrome is a disorder that affects the bones, skin, and several hormone-producing (endocrine) tissues.

People with McCune-Albright syndrome develop areas of abnormal scar-like (fibrous) tissue in their bones, a condition called polyostotic fibrous dysplasia. Polyostotic means the abnormal areas (lesions) may occur in many bones; often they are confined to one side of the body. Replacement of bone with fibrous tissue may lead to fractures, uneven growth, and deformity. When lesions occur in the bones of the skull and jaw it can result in uneven (asymmetric) growth of the face. Asymmetry may also occur in the long bones; uneven growth of leg bones may cause limping. Abnormal curvature of the spine (scoliosis) may also occur. Bone lesions may become cancerous, but this happens in fewer than 1 percent of people with McCune-Albright syndrome.

In addition to bone abnormalities, affected individuals usually have light brown patches of skin called café-au-lait spots, which may be present from birth. The irregular borders of the café-au-lait spots in McCune-Albright syndrome are often compared to a map of the coast of Maine. By contrast, café-au-lait spots in other disorders have smooth borders, which are compared to the coast of California. Like the bone lesions, the café-au-lait spots in McCune-Albright syndrome may appear on only one side of the body.

Girls with McCune-Albright syndrome may reach puberty early. These girls often have menstrual bleeding by age 2. This early onset of menstruation is believed to be caused by excess estrogen, a female sex hormone, produced by cysts that develop in one of the ovaries. Less commonly, boys with McCune-Albright syndrome may also experience early puberty.

Other endocrine problems may also occur in people with McCune-Albright syndrome. The thyroid gland, a butterfly-shaped organ at the base of the neck, may become enlarged (a condition called a goiter) or develop masses called nodules. About 50 percent of affected individuals produce excessive amounts of thyroid hormone (hyperthyroidism), resulting in a fast heart rate, high blood pressure, weight loss, tremors, sweating, and other symptoms. The pituitary gland (a structure at the base of the brain that makes several hormones) may produce too much growth hormone. Excess growth hormone can result in acromegaly, a condition characterized by large hands and feet, arthritis, and distinctive facial features that are often described as "coarse." Excess growth hormone secretion may also lead to increased expansion of the fibrous dysplasia in the bones, most visibly in the skull. Rarely, affected individuals develop Cushing syndrome, an excess of the hormone cortisol produced by the adrenal glands, which are small glands located on top of each kidney. Cushing syndrome causes weight gain in the face and upper body, slowed growth in children, fragile skin, fatigue, and other health problems. In people with McCune-Albright syndrome, Cushing syndrome occurs only before age 2.

Problems in other organs and systems, such as noncancerous (benign) gastrointestinal growths called polyps and other abnormalities, can also occur in McCune-Albright syndrome.

Russell-Silver syndrome is a growth disorder characterized by slow growth before and after birth. Babies with this condition have a low birth weight and often fail to grow and gain weight at the expected rate (failure to thrive). Head growth is normal, however, so the head may appear unusually large compared to the rest of the body. Affected children are thin and have poor appetites, and some develop recurrent episodes of low blood glucose (hypoglycemia) as a result of feeding difficulties. Adults with Russell-Silver syndrome are short; the average height for affected men is about 151 centimeters (4 feet, 11 inches) and the average height for affected women is about 140 centimeters (4 feet, 7 inches).

Many children with Russell-Silver syndrome have a small, triangular face with distinctive facial features including a prominent forehead, a narrow chin, a small jaw, and downturned corners of the mouth. Other features of this disorder can include an unusual curving of the fifth finger (clinodactyly), asymmetric or uneven growth of some parts of the body, and digestive system abnormalities. Russell-Silver syndrome is also associated with an increased risk of delayed development, speech and language problems, and learning disabilities.