The pituitary, a pea-sized gland, is part of the endocrine system. It is located at the base of the brain deep in the center of the skull where it hangs from the hypothalamus by a thread-like stalk. Known as the "master gland of the body," it synthesizes, stores and releases many hormones that control the function of other glands in the body, including the thyroid gland, adrenal glands, ovaries and testes. The pituitary sends signals to these other glands telling them to produce thyroid hormone, cortisol, estrogen, testosterone, and other hormones.

Hormones and their Function

The gland itself consists of a larger anterior lobe that makes the following hormones: adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH) and Prolactin. The posterior lobe releases two hormones, oxytocin and vasopressin (ADH) that are produced in the hypothalamus. The hypothalamus relays signals from many parts of the brain to the pituitary, which in turn sends its own messages to various parts of the body.

ACTH is made in the pituitary gland and travels through the bloodstream to the adrenal glands. It stimulates the adrenals to release cortisol, a key factor in many functions in the body's metabolism of fats, carbohydrates, sodium, potassium, and protein as well as blood pressure.

• TSH causes the thyroid gland to produce two hormones, triiodothyronine (T3) and thyroxine (T4), which help control the body's metabolism.
• LH and FSH control the production of testosterone, estrogen, sperm, and egg maturation and release.
• GH is a major participant in control of several complex physiologic processes, including growth and metabolism.
• Prolactin stimulates the production of breast milk and is necessary for normal milk production during breastfeeding.
• Oxytocin is responsible for stimulation of milk ejection (milk letdown) and for stimulation of uterine smooth muscle contraction at birth.
• ADH is the primary regulator of body water.

Pituitary tumors are abnormal growths of cells found in the pituitary gland. They are not brain tumors. Benign tumors, called adenomas, are the most common cause of pituitary disorders. They grow slowly and do not spread to other parts of the body. Although they are not cancer, some pituitary tumors can cause harm because they compress and damage normal pituitary tissue, interfering with hormone production, thus causing the pituitary gland to produce excess or reduced levels of hormones—which in turn causes problems throughout the body.

Some pituitary tumors grow large enough to press on or invade surrounding structures such as the optic nerve, causing loss of vision, for example. It is estimated that 10-25 percent of the US population has some form of small pituitary tumor, an adenoma 2-3mm, but most of these people suffer no ill effects from the tumor. Although they can occur in any age patient, most of the tumors are found in older people and are more common in women than in men. The causes for the vast majority of pituitary tumors are unknown.

Other tumors that appear in this area, called the sellar/parasellar region, include craniopharyngiomas, germ cell tumors, and epidermoid cysts, which are tumors that arise from developmental cells; meningiomas, tumors of the protective covering of the brain; gliomas, tumors that arise from the supporting cells in the brain; and metastatic tumors that originate in another part of the body and spread to the brain.

More than a dozen different disorders result from pituitary tumors and disease. Thus, diagnosis can be a challenge and pituitary disease can be frustrating for the patient. Early detection is optimal so the tumor can be treated or removed before it causes serious problems by putting pressure on the brain or causing serious hormonal imbalances. Evaluation and treatment often involves a team of physicians including a neurosurgeon and endocrinologist, and sometimes a neurologist, radiologist, radiation oncologist, and otorhinolaryngologist. Surgery is a common treatment, with the success rate greater in smaller tumors. Early treatment and diagnosis are keys to success.

Symptoms arise when the tumors cause either excess or reduced production of pituitary hormones or when the tumor presses on adjacent structures. Symptoms and changes in bodily function vary depending upon which lobe of the pituitary gland is affected and the type of tumor.

Excessive Hormone Production

Functional adenomas overproduce one or more hormones and have characteristic sets of clinical features.

ACTH producing tumors cause the pituitary gland to secrete increased amounts of ACTH, stimulating an overproduction of cortisol by the adrenal glands. This pituitary condition, known as Cushing's disease, causes a variety of symptoms, including weight gain, often in the abdomen, upper back and neck, exaggerated facial roundness and acne; skin may become fragile and thin, bruise easily, heal poorly, and develop purplish pink stretch marks. Muscle loss results in thinning arms and legs, and muscle weakness may occur, causing severe fatigue. Loss of bone mass causes osteoporosis. High blood pressure and high blood sugar, irritability, anxiety, depression, difficulty with concentration, memory and sleep are common. Women usually have excess hair growth on their faces and bodies. Men may experience sexual dysfunction.

TSH secreting tumors cause overproduction of TSH, which stimulates the thyroid glands to make too much thyroid hormone, thyroxine, causing hyperthyroidism. This condition accelerates metabolism and can result in weight loss, rapid heartbeat and breathlessness, decreased concentration, tremor, fatigue coupled with difficulty sleeping, nervousness, heat intolerance and excessive sweating, increased bowel movements and light or absent menstrual periods.

GH producing tumors produce excess growth hormone, which results in a condition known as acromegaly. Physical changes caused by this tumor occur gradually: enlarging of the hands and feet, broadening of the brow and nose, changes in the jaw/bite, sleep apnea, high blood pressure, diabetes mellitus (high blood sugar), oily skin, acne and excessive sweating.

Prolactin-producing tumors (prolactinomas) account for about half of pituitary adenomas. They can cause a decrease in normal levels of sex hormones, estrogen in women and testosterone in men. Men may experience enlarged breasts and decrease of body hair, erectile dysfunction or impotence, infertility and loss of interest in sexual activity. Women may experience irregular or lack of menstrual periods, infertility and inappropriate breast milk production. Post-menopausal women suffer headaches and visual problems.

Reduced Hormone Production

Pituitary hormone deficiency is usually caused by a benign pituitary tumor pressing on and destroying the cells of the pituitary gland. All of the hormones except prolactin can be replaced by medications—pills, injections, nasal spray, skin patches and/or skin gel, depending on the type of hormone.

ACTH deficiency means that the hormone is not stimulating the adrenal glands to produce cortisol, necessary in the regulation of blood pressure and cardiovascular function as well as regulation of the body's use of proteins, carbohydrates, and fats.

Adrenal insufficiency affects blood pressure, bone density, kidney function, and metabolism. The patient may suffer fatigue, stomach pain and weight loss, nausea and vomiting, especially in the morning, low blood pressure, dizziness and even loss of consciousness. Cortisol is necessary for life.

TSH deficiency means that the thyroid gland is not stimulated to make enough thyroid hormone, which is necessary for maintaining normal body metabolism. Because this hormone affects the function of so many bodily systems—nervous, digestive, endocrine, as well as the function of the heart, lungs, blood cells, bone and muscle, and response to stress, this hormone is necessary for life. Low thyroid, hypothyroidism, results in fatigue, weight gain, memory problems, constipation, cold-intolerance, hair loss, water retention and more.

GH deficiency is the most common pituitary hormone deficiency. Children suffering from this deficiency may have growth retardation and short stature. Adults lacking growth hormone have decreased energy, loss of bone density and thus an increased risk of bone fracture, accumulation of fat and decrease in muscle mass.

Tumors that cause a deficiency of ADH affect water and sodium balance. Insufficient ADH causes excessive and frequent urination and extreme thirst. The patient must drink large amounts of water to prevent blood sodium levels from increasing abnormally and causing dehydration.

LH and FSH deficiencies cause a decrease in normal levels of sex hormones, estrogen in women and testosterone in men. Women experience menstrual irregularities, infertility, bone loss, hot flashes and deceased sexual interest. Men may experience enlarged breasts and decrease of body hair, testicle size, muscle mass, bone density, energy, interest in sex; they may also suffer from impotence.

Prolactin deficiency renders women unable to nurse after pregnancy.

Pituitary tumors can cause a wide variety of symptoms because of the hormonal influence of the gland and because of its location near the brain. Thus, diagnosis of pituitary disease is often problematical because it is often confused with the symptoms, not the primary source of the symptoms. Patients consistently and inexplicably suffering from three or more of the following symptoms should be examined for a pituitary tumor: aching joints, carpal tunnel syndrome, disrupted menses, depression, early menopause, easy bruising, fatigue, growth problems, headache, inappropriate lactation, infertility, muscle weakness, obesity, osteoporosis, vision problems.

In diagnosing what could be a pituitary problem, the physician should take a complete medical history and do a physical examination. Further tests will include measurement of hormones in the blood and/or urine, and imaging studies. Two non-invasive studies are a CT or CAT scan to detect any abnormalities that do not appear on an ordinary x-ray, and/or an MRI, which produces three dimensional images of an internal organ or structure of the body, including the brain and spinal cord. The MRI can detect some tumors a fraction of an inch in size but other microadenomas may not appear. Additional tests include vision testing to determine if growth of a pituitary tumor has impaired the patient's vision and an x-ray of a child's hand and wrist to measure whether bone growth is normal.