endocrine and metabolic disorders
Gigantism and Acromegaly
Diagnosis of Gigantism and Acromegaly
CT or MRI Insulin-like growth factor 1 (IGF-1) levels Usually growth hormone levels Diagnosis can be made from the characteristic clinical findings. MRI of the sella is the imaging test of choice for diagnosis of pituitary adenoma. CT, MRI, or skull x-rays disclose cortical thickening, enlargement of the frontal sinuses, and enlargement and erosion of the sella turcica. X-rays of the hands show tufting of the terminal phalanges and soft-tissue thickening. Serum IGF-1should be measured in patients with suspected acromegaly; IGF-1 levels are typically substantially elevated (3-fold to 10-fold), and because IGF-1 levels do not fluctuate like GH levels do, they are the simplest way to assess GH hypersecretion. IGF-1 levels also can be used to monitor response to therapy. Plasma GH levelsare typically elevated. Blood should be taken before the patient eats breakfast (basal state); in normal people, basal GH levels are low or undetectable. Transient elevations of GH are normal, due to the pulsatile secretion of GH, and must be distinguished from pathologic hypersecretion. The degree of GH suppression after a glucose load remains the standard and thus should be measured in patients with elevated plasma GH; however, the results are assay-dependent, and the cutoff for normal suppression is controversial. Secretion in normal people is suppressed to<1 ng/mL ([< 1 mcg/L]; a cutoff of<0.4 ng/mL [< 0.4 mcg/L] is often used) within 120 minutes of oral administration of 75 g of glucose. Most patients with acromegaly have substantially higher values. In some cases, basal plasma GH levels are also used in monitoring response to therapy. CTorMRIof the sella should be done to look for a tumor. If a tumor is not visible, excessive secretion of pituitary GH may be due to a non-central nervous system tumor producing excessive amounts of ectopic GHRH. Demonstration of elevated levels of plasma GHRH can confirm the diagnosis. Lungs and pancreas may be first evaluated in searching for the sites of ectopic production. Screening for complications, including Diabetes Mellitus (DM) , heart disease, and gastrointestinal cancer, should be done at the time of diagnosis. Fasting plasma glucose levels, glycosylated Hb (HbA1C), or an oral glucose tolerance test can be done to test for diabetes. Electrocardiography and, preferably, echocardiography are done to detect heart disease. Colonoscopy is done to detect colon polyps and cancer. Follow-up screening depends on the results of the initial testing and the patient's response to treatment. 