Acromegaly and gigantism
Acromegaly and gigantism: Excerpt from Professional Guide to Diseases (Eighth Edition)
Acromegaly and gigantism are chronic, progressive diseases marked by hormonal dysfunction and startling skeletal overgrowth. Acromegaly occurs after epiphyseal closure, causing bone thickening and transverse growth and visceromegaly. Gigantism begins before epiphyseal closure and causes proportional overgrowth of all body tissues. Although the prognosis depends on the causative factor, these disorders usually reduce life expectancy unless treated in a timely fashion.
Causes and incidence
Typically, oversecretion of human growth hormone (hGH) produces changes throughout the body, resulting in acromegaly and, when oversecretion occurs before puberty, gigantism. Eosinophilic or mixed-cell adenomas of the anterior pituitary gland may cause this oversecretion but the etiology of the tumors themselves remains unclear. Occasionally, hGH levels are elevated in more than one family member, which suggests the possibility of a genetic cause.
The earliest clinical manifestations of acromegaly include soft-tissue swelling of the extremities and coarsening of facial features. This rare form of hyperpituitarism occurs equally among males and females, usually between ages 30 and 50. Annually, it affects 3 to 4 people per every million.
In gigantism, proportional overgrowth of all body tissues starts before epiphyseal closure. This causes remarkable height increases of as much as 6"(15 cm) per year. Gigantism affects infants and children, causing them to attain as much as three times the normal height for their age. As adults, they may ultimately reach a height of more than 80"(203 cm). Gigantism is rare; there have only been 100 reported cases.
Signs and symptoms
Acromegaly develops slowly and typically produces diaphoresis, oily skin, hypermetabolism, and hypertrichosis. Severe headache, central nervous system impairment, bitemporal hemianopia, loss of visual acuity, and blindness may result from the intrasellar tumor compressing the optic chiasm or nerves.
Hypersecretion of hGH produces cartilaginous and connective tissue overgrowth, resulting in a characteristic hulking appearance, with an enlarged supraorbital ridge and thickened ears and nose. Prognathism, projection of the jaw, becomes marked and may interfere with chewing. Laryngeal hypertrophy, paranasal sinus enlargement, and thickening of the tongue cause the voice to sound deep and hollow. Distal phalanges display an arrowhead appearance on X-rays, and the fingers are thickened. Irritability, hostility, and various psychological disturbances may occur.
Prolonged effects of excessive hGH secretion include bowlegs, barrel chest, arthritis, osteoporosis, kyphosis, hypertension, and arteriosclerosis. Both gigantism and acromegaly may also cause signs of glucose intolerance and clinically apparent diabetes mellitus because of the insulin-antagonistic character of hGH. If acromegaly is left untreated, the patient is at risk for premature cardiovascular disease, colon polyps, and colon cancer.
Gigantism develops abruptly, producing some of the same skeletal abnormalities seen in acromegaly. As the disease progresses, the pituitary tumor enlarges and invades normal tissue, resulting in the loss of other trophic hormones, such as thyroid-stimulating hormone, luteinizing hormone, follicle-stimulating hormone, and corticotropin, thus causing the target organ to stop functioning.
Diagnosis
Plasma hGH and somatomedin-C levels measured by radioimmunoassay typically are elevated.Because hGH secretion is pulsatile, the results of random sampling may be misleading. The glucose suppression test offers more reliable information. Glucose normally suppresses hGH secretion; therefore, a glucose infusion that doesn’t suppress the hormone level to below the accepted normal value of 5 ng/ml, when combined with characteristic clinical features, strongly suggests hyperpituitarism. The level of insulin-like growth factor 1 is high.
In addition, skull X-rays, computed tomography scan, arteriography, and magnetic resonance imaging determine the presence and extent of the pituitary lesion. Bone X-rays showing a thickening of the cranium (especially of frontal, occipital, and parietal bones) and of the long bones, as well as osteoarthritis in the spine, support this diagnosis.
Treatment
Treatment aims to curb overproduction of hGH through removal of the underlying tumor by cranial or transsphenoidal hypophysectomy or pituitary radiation therapy. In acromegaly, surgery is mandatory when a tumor causes blindness or other severe neurologic disturbances. Postoperative therapy often requires replacement of thyroid, cortisone, and gonadal hormones. Adjunctive treatment may include administration of bromocriptine or cabergoline and octreotide and postoperative conventional proton beam radiation, which inhibit hGH synthesis. The therapeutic goal is to reach and maintain hGH levels less than 2 ng/dl, because at that level, life expectancy is restored to that of age-matched controls.
Special considerations
The extreme body changes characteristic of this disorder can cause severe psychological stress; therefore, emotional support to help the patient cope with his altered body image is an integral part of patient care.
❑ Assess for skeletal manifestations, such as arthritis of the hands and osteoarthritis of the spine. Administer medications as ordered. To promote maximum joint mobility, perform or assist with range-of-motion exercises.
❑ Evaluate muscle weakness, especially in the patient with late-stage acromegaly. Check the strength of his handclasp. If it’s very weak, help with tasks such as cutting food.
❑ Keep the skin dry. Avoid using an oily lotion because the skin is already oily.
❑ Test blood for glucose. Check for signs of hyperglycemia (fatigue, polyuria, and polydipsia).
❑ Be aware that the tumor may cause visual problems. If the patient has hemianopia, stand where he can see you. Remember, this disease can also cause inexplicable mood changes. Reassure the family that these mood changes result from the disease and can be modified with treatment.
❑ Before surgery, reinforce what the surgeon has told the patient, and try to allay the patient’s fear with a clear and honest explanation of the scheduled operation.
PEDIATRIC TIP If the patient is a child, explain to his parents that such surgery prevents permanent soft-tissue deformities but won’t correct bone changes that have already taken place. Arrange for counseling, if necessary, to help the child and his parents cope with these permanent defects.
Alert After surgery, diligently monitor vital signs and neurologic status. Immediately report increased urinary output lasting over 2 hours, alteration in level of consciousness, unequal pupil size, changes in visual acuity, vomiting, falling pulse rate, or rising blood pressure. These changes may signal an increase in intracranial pressure due to intracranial bleeding or cerebral edema.
❑ Check blood glucose level often. Remember, hGH levels usually fall rapidly after surgery, removing an insulin-antagonist effect in many patients and possibly precipitating hypoglycemia. Measure intake and output hourly, and report large increases. Transient diabetes insipidus, which sometimes occurs after surgery for hyperpituitarism, can cause such increases in urine output.
❑ If the transsphenoidal approach is used, a large nasal packing is kept in place for several days. Because the patient must breathe through his mouth, give good mouth care. Pay special attention to the mucous membranes — which usually become dry — and the incision site under the upper lip, at the top of the gum line. The surgical site is packed with a piece of tissue generally taken from a midthigh donor site. Watch for cerebrospinal fluid leaks from the packed site, which may necessitate additional surgery to repair the leak. Look for increased external nasal drainage or drainage into the nasopharynx.
❑ Encourage the patient to walk as soon as possible after surgery.
❑ Before discharge, emphasize the importance of continuing hormone replacement therapy, if ordered. Make sure the patient and his family understand which hormones are to be taken and why as well as the correct times and dosages. Warn against stopping the hormones suddenly.
❑ Advise the patient to wear a medical identification bracelet at all times and to bring his hormone replacement schedule with him whenever he returns to the health care facility.
❑ Instruct the patient to have follow-up examinations for the rest of his life because a slight chance exists that the tumor that caused his condition may recur.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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