Acromegaly and gigantism
Acromegaly and gigantism: Excerpt from Handbook of Diseases
Chronic, progressive diseases, acromegaly and gigantism are 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 way.
Causes
Typically, oversecretion of human growth hormone (HGH) produces changes throughout the entire body, resulting in acromegaly and, when oversecretion occurs before puberty, gigantism. Somatotrope adenomas and, rarely, extrapyradimal pituitary lesions or other tumors may cause this oversecretion, but the cause of the tumors themselves remains unclear. Elevated HGH levels in more than one family member suggest a genetic cause.
The earliest sign of acromegaly is soft-tissue swelling of the extremities, which causes coarsening of the facial features. This rare form of hyperpituitarism occurs equally among men and women, usually between ages 30 and 50.
AGE ALERT: In gigantism, proportional overgrowth of all body tissues starts before epiphyseal closure. This causes remarkable height increases of as much as 6 " (15.2 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 "(203.2 cm).
Signs and symptoms
Acromegaly develops slowly, whereas gigantism develops abruptly.
Acromegaly
Acromegaly commonly produces hyperdidrosis, arthropathy, carpal tunnel syndrome, proximal muscle weakness and fatigue, acanthosis nigricans and skin tags, and oily skin.
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. Also, the fingers are thickened.
Coronary artery disease, cardiomyopathy with arrhythmias, left ventricular hypertrophy, decreased diastolic function, and hypertension occur in 30% of patients; upper airway obstruction with sleep apnea, in 60% of patients. Generalized visceromegaly occurs, including cardiomegaly, macroglossia, and thyroid gland enlargement.
Prolonged effects of excessive HGH secretion include barrel chest and kyphosis. Both gigantism and acromegaly may also cause signs of glucose intolerance and diabetes mellitus because of the insulin-antagonistic character of HGH.
Gigantism
Gigantism produces 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
Serum HGH levels measured by radioimmunoassay typically are elevated. However, because HGH secretion is pulsatile, the results of random sampling may be misleading. IGF-1 (somatomedin-C) levels offer a better screening alternative.
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 2 ng/ml, when combined with characteristic signs and symptoms, strongly suggests hyperpituitarism.
In addition, skull X-rays, a 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
Overproduction of HGH is curbed through removal of the underlying tumor by cranial or transsphenoidal hypophysectomy or pituitary radiation therapy. With acromegaly, surgery is mandatory when a tumor causes blindness or another severe neurologic disturbance.
Postoperative therapy commonly requires replacement of thyroid and gonadal hormones and cortisone. Adjunctive treatment may include administration of lanreotide, bromocriptine, and octreotide, which inhibit HGH synthesis.
Special considerations
Grotesque body changes characteristic of this disorder can cause severe psychological stress. Provide the patient with emotional support to help him cope with an altered body image.
Examine the patient for skeletal changes, and promote maximum joint mobility with range-of-motion exercises.
Evaluate the patient for muscle weakness. Check the strength of his handclasp. If it’s weak, help with tasks such as cutting food.
Keep the patient’s skin dry. Avoid using an oily lotion because the skin is already oily.
Monitor the patient’s serum glucose level. Check for signs and symptoms of hyperglycemia, including fatigue, polyuria, and polydipsia.
Be aware that the tumor may cause visual problems. If the patient has hemianopia, stand where he can see you.
Keep in mind that 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, if possible, and try to allay the patient’s fear.
AGE ALERT: 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 parents cope with these permanent defects.
After surgery, diligently monitor the patient’s vital signs and neurologic status. Be alert for any alteration in level of consciousness, pupil equality, or visual acuity as well as 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 levels 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 watch for 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 pack 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 (CSF) leaks from the packed site. Look for increased external nasal drainage or drainage into the nasopharynx. CSF leaks may necessitate additional surgery to repair the leak.
Encourage the patient to get out of bed and walk around on the 1st or 2nd day after surgery.
As appropriate, before the patient is discharged, emphasize the importance of continuing hormone replacement therapy. Make sure the patient and his family understand which hormones are to be taken and why, as well as the correct times and dosages.
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 facility.
Instruct the patient to have follow-up checkups for the rest of his life because the tumor that caused his condition could recur.
CLINICAL TIP: A patient with acromegaly should be periodically screened for colon polyps because the incidence of polyps increases with chronic elevated HGH levels.
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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