Page 55 Complete Your CE Test Online - Click Here What pituitary hormone is secreted in response to a state of dehydration? ADH (antidiuretic hormone) release is stimulated by dehydration and increased plasma osmolarity. ADH controls water loss by the kidneys. It facilitates water reabsorption in the distal convoluted tubules and collecting ducts of the kidneys. Controlled by negative feedback, ADH release is stimulated by dehydration and increased plasma osmolarity [3] . What is the major role of the thymus? The major role of the thymus seems to be related to the immune system since it produces T cells, which are critical to cell-mediated immunity[1] . The endocrine system depends on both negative and positive feedback. Differentiate between negative and positive feedback. The endocrine system depends on both negative and positive feedback for its regulation. Negative feedback takes place when the rate of production of a particular product decreases as the concentration of that product increases. Negative feedback manages the rate of production to avoid accumulation of a particular product. For example, as the amount of some hormones reach the desired level, the body stops or reduces the rate of their production to avoid excessive accumulation[1,3] . Positive feedback occurs when the rate of production of a particular product increases as the concentration of that product increases. Positive feedback is less common in the body than negative feedback. An example of positive feedback is the secretion of oxytocin that stimulates uterine muscle contraction during labor. As labor progresses, pressure on the cervix continues to stimulate oxytocin release, which continues to stimulate uterine muscle contraction[3] . Hypopituitarism is a rare disorder that usually presents as a rather slow, predictable pattern of hormonal failures. What are the clinical manifestations of this disease? Why do they occur? The pituitary gland secretes TSH, FSH, LH, GH, ACTH, prolactin, ADH, and oxytocin[1,4] . Clinical manifestations depend on the severity of the disease and on the number of hormones that are deficient. Presenting signs and symptoms usually begin with hypogonadism because of decreased FSH and LH levels. In adults, this causes females to stop menstruating, and decreases libido in males. Signs and symptoms of GH deficiency usually follow including osteoporosis, lethargy, subtle emotional changes, adverse lipid changes, and decreased lean-to-fat body mass[4,5] . In children, lack of GH leads to short stature, delayed growth, delayed puberty, and, possibly dwarfism. If hypopituitarism occurs before puberty, the development of secondary sex characteristics is prevented. In males, this means lack of facial and body hair, undersized penis, testes, and prostate gland, and failure to initiate and maintain an erection. In females, there is a lack of pubic and axillary hair, failure to develop mature breasts, and primary amenorrhea[4,5] . It is important to note that clinical signs and symptoms of hypopituitarism do not usually become apparent until 75% of the gland is destroyed[5] . Hypopituitarism that involves all of the pituitary hormones is called _______________________. Panhypopituitarism. It is characterized by involvement of all pituitary hormones. However, it is more likely that only one or more pituitary hormones are involved. This leads to only isolated or partial hypopituitarism[4] . Clinical signs and symptoms of hypopituitarism do not usually become apparent until 75% of the gland is destroyed[5] . What causes dwarfism in children? What signs and symptoms first indicate dwarfism and when do they appear? In children, lack of GH causes short stature, delayed growth, delayed puberty, and, possibly, dwarfism [4,5] . Dwarfism is not often evident at birth but initial signs and symptoms appear in the first few months of life, and by six months growth retardation is apparent[5] . Danielle has been diagnosed with acromegaly. What endocrine gland disorder causes this disorder? What clinical manifestations are associated with this disease? How is it treated? Acromegaly is formally known as hyperpituitarism and is a chronic, progressive disease characterized by hormonal dysfunction and disturbing skeletal overgrowth. Hyperpituitarism also causes giantism. The difference between acromegaly and gigantism is the age of the person affected. Acromegaly affects adults and has a slow, gradual progression. Overgrowth of cartilage and connective tissue, a big nose, enlarged hands and feet, thickened lips, tongue, gingers, and ear, and changes in the shape of the face are characteristic features. The voice deepens, the skin becomes coarse, oily, and thick, and there is extreme diaphoresis. A variety of mood changes and mental health disturbances may occur. Acromegaly affects males and females equally, usually between the ages of 30 and 50[5,8] . Gigantism can affect infants and children and is a very rare disorder, affecting only 100 persons to date. Affected children may reach as much as three times the normal height for their age[5] . The most common cause of excessive GH production is a tumor, usually a benign adenoma of the pituitary gland. Treatment involves surgical removal of the tumor and reducing GH production. Removal of a pituitary is complex and should be performed only by surgeons who are experienced in this type of surgery. If the entire tumor cannot be removed via surgery, radiation may be needed to destroy remaining tumor cells and reduce GH levels. Various medications may be prescribed to lower production or block the action of GH. Since acromegaly progresses so slowly, what is one way that patients and families actually notice changes in the patient’s physical appearance? Since the disease develops so slowly some people may notice physical changes in appearance only by comparing old and current photographs [8] . Several endocrine disorders interfere with normal levels of GH. Therefore, it is important to remember what important point when obtaining blood samples for GH suppression test? Patients should not be emotionally or physically stressed when obtaining blood samples for the GH suppression test since stress can elevate GH levels[9] . What is stereotactic radiosurgery? Why is it performed? Who should perform it? Stereotactic radiosurgery is also known as Gamma Knife radiosurgery. It is performed in order to direct radiation at tumor cells. For example, in cases of acromegaly when it is necessary to destroy pituitary tumor cells and to gradually reduce GH levels, stereotactic radiosurgery may be used. A high dose of radiation directed at the tumor cells is administered in a single dose while limiting radiation exposure to surrounding normal cells. This type of radiation therapy may bring GH levels to within normal limits within three to five years. Administration of stereotactic radiosurgery requires an extremely high level of technical skill and is available at only a few United States health care facilities. Mark is a healthy 30-year-old sales manager at a luxury car dealership. While accompanying a potential buyer on a test-drive, a motorcycle runs a red light and crashes into Mark’s car. The airbag deploys and strikes Mark’s head with considerable force. Mark is evaluated at the hospital and diagnosed with a mild concussion. Three days later Mark returns to work feeling fine and resumes his busy schedule. However, later in the afternoon, Mark complains of feeling dizzy and weak. He is extremely thirsty and begins to void large quantities of urine. Mark leaves work early, telling his boss that he is too tired even to drive himself home. His wife arrives to take him home. Alarmed she insists that he see their family physician. Upon arrival at the doctor’s office Mark heads straight for the nearest bathroom, overwhelmed by an urgent need to void. His doctor arranges for Mark to be transported to the hospital for further evaluation. Mark is found to have a subdural hematoma that is increasing intracranial pressure. In addition to the subdural hematoma, what is causing some of Mark’s symptoms? Why have they occurred? What treatment is needed? Mark is exhibiting signs of diabetes insipidus, a water metabolism disorder due to a deficiency of antidiuretic hormone (AHD). There are several types of diabetes insipidus. Central diabetes insipidus is the result of intracranial neoplastic tumors, metastatic lesions, surgical removal of the pituitary, skull fracture, or, as in Mark’s case, head trauma. The cerebral hematoma is causing intracranial pressure. Once that pressure is relieved, Mark’s symptoms will most likely stop as quickly as they began[5,11] . Prognosis is good since relieving the intracranial pressure is the focus of treatment for Mark. He will also need fluid replacement and supportive