The pea-sized pituitary gland, or “master gland”, is part of the endocrine system, which helps to regulate and maintain many different body functions by synthesizing (making) and releasing hormones. The pituitary gland is located in a bony chamber at the base of the brain, is suspended by a stalk from the hypothalamus,and is located behind the sphenoid sinus, which is behind the nose. The pituitary gland is made of two lobes: the large anterior (front) pituitary lobe and the posterior (rear) lobe.
The frontal lobe controls the production and secretion of 6 hormones. Growth hormone, as its name implies, regulates the physical growth of most parts of your body. Prolactin stimulates the breasts to produce milk. The four other hormones made by the frontal lobe (i.e. thyroid-stimulating hormone (TSH), corticotropin (ACTH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH)) stimulate other endocrine glands, which in turn affect metabolism.
The rear lobe governs the body’s fluid balance by storing and releasing antidiuretic hormone (ADH) and oxytocin, both of which are made in the hypothalamus directly above the pituitary gland.
Diseases of the Pituitary
A variety of symptoms and conditions can be the result of a malfunctioning pituitary gland. This malfunctioning can be due to a pituitary tumor or due to other disease that interferes with the hormone producing and releasing function of the pituitary gland. Please see Endonasal Endoscopic Approach for a new, minimally invasive way to address pituitary tumors.
In this rare condition, the pituitary gland produces too much growth hormone, which causes excessive growth. However, an adult cannot grow taller, since the bones mature and vertical growth stops at the end of adolescence. Instead, the excess growth hormone produces acromegaly, in which your bones thicken and all other structures and organs grow larger. Overproduction of growth hormone is usually caused by a Pituitary tumor.
Acromegaly generally can occur at any time after adolescence. Usually, the first symptom is enlargement of the hands and feet, typically revealed by the tightening of a ring on the finger, or an increase in glove or shoe size.
After the hands and feet increase in size, the head and neck grow broader, and the lower jaw, brows, nose, and ears become prominent. The skin and tongue thicken, and features become generally coarser. The voice may become deeper. Many people with this disorder experience tingling in the hands, fatigue, headaches, increased sweating, stiffness, and generalized aches. In a woman, the amount of hair on the body and limbs may increase.
In some cases of acromegaly, Diabetes mellitus develops. If a large pituitary tumor is present, it may cause a number of other symptoms. The longer acromegaly is left untreated, the greater the risks become. The heart continues to enlarge; high blood pressure and possibly heart failure develop in time. Furthermore, a large pituitary tumor can cause serious problems with the eyesight. Finally, certain cancers are more common in people who have acromegaly.
Gigantism is basically the same disorder as Acromegaly, except that it begins in children and adolescents instead of in adults. In both Acromegaly and Gigantism, the pituitary gland overproduces growth hormone, usually because of a pituitary tumor, which causes excessive growth of all parts of the body. The main difference between the two forms of the disease is that acromegaly occurs when the arm and leg bones have stopped growing in length, and gigantism occurs when they are still growing so that the young person grows to giant proportions. Treatment is the same as acromegaly.
Diabetes insipidus is a condition in which the kidneys are unable to maintain adequate amounts of water in the body. It is characterized by excessive thirst and excessive secretion of very diluted urine.
In the normal production of urine, your kidneys filter water and other substances from your blood, and then reabsorb much of the filtered water, leaving urine ready to be excreted from your body. The absorbed water is returned to the bloodstream to maintain the correct concentrations of minerals, proteins, and other nutrients in blood and body fluids. Normally, the amount and concentration of urine is related to your fluid intake. If you lose a lot of fluids due to e.g. fever, sweating, vomiting, or diarrhea, the kidneys reabsorb almost all of the filtered water from your blood and only a small amount of concentrated urine is excreted. On the other hand, if you drink large amounts of water, the kidneys reabsorb less filtered water, and a large amount of dilute urine is produced.
The process of water reabsorption by the kidneys is regulated by antidiuretic hormone (ADH), a hormone that is produced in the hypothalamus released by the posterior lobe (rear part) of the pituitary gland. Diabetes insipidus is a disorder in which there is a deficiency of ADH, causing your body to pass large quantities of heavily diluted urine, even if fluid intake is reduced.
The most common cause of the disorder is damage to the pituitary gland from a severe head injury. The condition may also result from scarring or damage caused by an operation on the pituitary gland, or may be due to the effects of radiation therapy on the gland or on the surrounding area. In unusual cases, diabetes insipidus is caused by pressure on the posterior lobe of the gland from a pituitary tumor.
In a different form of the disorder, called nephrogenic diabetes insipidus, the condition results from an insensitivity of the kidney tubules to ADH. In this condition, the level of pituitary secretion of ADH is normal.
The main symptom of diabetes insipidus is that you pass large quantities of colorless urine, as much as 21 qt (20 liters) every 24 hours. This great fluid loss results in an unquenchable thirst. You will constantly be interrupted during the day and awakened at night by the strong need to urinate and drink. Potentially fatal dehydration can occur rapidly. Hormone tests to access ADH function are done by an endocrinologist and they will confirm the diagnosis.
The treatment of diabetes insipidus is the use of a synthetic form of ADH, taken either as nose drops or by injection. The length of time you must take the drops or receive the injections is determined mainly by what has caused the disorder. If it was caused by a head injury, surgery, or radiation therapy, the defective gland may return to normal within a year, and symptoms will go away. If this fails to happen, you may have to take medication for the rest of your life. If the disorder is caused by a pituitary tumor, the tumor will probably have to be removed (see Endonasal Endoscopic Approaches to Pituitary Tumor).
In the nephrogenic form of the disorder, you may only need to restrict your salt intake and take certain diuretics or other medication to help your kidneys conserve water.
Galactorrhea is a condition in which breast milk is being produced when it is not supposed to be produced. Normally, milk production only occurs in a woman a few days before, and in the months following, the birth of a baby. Production at any other time in a woman, and at any time in a man, is called galactorrhea. Galactorrhea is not a serious threat to health, although it may be annoying. In women, galactorrhea is often coupled with an absence of periods.
Galactorrhea is uncommon in women and even more rare in men. There are different underlying problems that can cause galactorrhea. Often, it is caused by excessive amounts of the female sex hormone estrogen, which can occur during pregnancy or from taking oral contraceptives or some other medications. In males, low testosterone can be a cause for galactorrhea. Another possible cause is excessive production of the hormone prolactin. Prolactin is made by the pituitary gland and stimulates milk production. Galactorrhea can also be caused by a disorder of the pituitary gland such as a tumor. In this case, while galactorrhea itself is generally harmless, the tumor can cause other problems over time and needs addressed.
In order to eliminate the possibility of a pituitary tumor or another underlying disorder, the endocrinologist will probably refer you for diagnostic tests, which may include a MRI scan and blood and urine tests.
If tests fail to reveal any cause for the condition, you will probably not need any treatment. If the problem is caused by drugs, discontinuing the drugs will clear it up. If galactorrhea is caused by a pituitary gland disorder or some other disease, the endocrinologist may prescribe hormone treatment or the drug bromocriptine to prevent milk production. If the cause is a pituitary tumor, you will be referred to Dr. Maroon or another qualified neurosurgeon for possible surgery.
As mentionned before, the pituitary gland is divided into two parts, the anterior (frontal) lobe and the posterior (rear) lobe. Pituitary gland tumors almost always occur in the anterior lobe. More than 10 percent of all tumors inside the skull develop in the pituitary gland. There are two main types of pituitary tumors:
Pituitary adenomas are overgrowths of one or more of the cell types in the gland. These tumors are almost always benign, and most are less than ½ inch (12 mm) in size. But, because they grow in a confined space (the pituitary gland is located in a boney chamber in the brain base) the benign tumor can run out of room and may damage the nerves from the eyes, and they can cause headaches and eventually serious brain disorders if they begin to increase further in size.
About 50 percent of all pituitary adenomas secrete abnormal amounts of the hormone prolactin (prolactinomas). The effect of this can range from no symptoms at all to impotence, absence of menstrual periods, or galactorrhea. Pituitary adenomas may also secrete other hormones, and this can lead to some of the diseases described above as well as Cushing’s syndrome. If the tumor enlarges, it an press upon surrounding areas, causing a variety of other problems. The causes of pituitary tumors are unknown. The incidence is 1 out of 10,000 people.
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