Acromegaly is most often caused by a somatotroph adenoma of the pituitary gland. Infrequently, these adenomas co-secrete other hormones. Transsphenoidal resection is the treatment of choice for these adenomas, especially when they cause visual impairment. The role of medical therapy has not been clearly established as primary treatment, but medical therapy is often used when surgery carries an unacceptable risk. Studies have shown that treatment with somatostatin analogues decreases IGF-1 levels and also decreases adenoma size. However, these studies have measured the outcomes at a minimum of 3 months. We report a unique case of acromegaly due to a somatotroph adenoma with a dramatic response to octreotide within 1 week. A 53-year-old woman with a history of multiple myeloma, colon cancer, and recent-onset diabetes mellitus was referred to our institution for headaches, blurry vision, left visual field cut, decreased hearing, and ataxia. MRI of the brain revealed a large, lobulated homogeneous enhancing mass extending superiorly and posteriorly from the clivus, causing compression of the optic chiasm as well as encasing bilateral carotid arteries. Biopsy of the mass revealed a pituitary adenoma with staining strongly positive for chromogranin and prolactin along with focal GH, LH, and FSH immunoreactivity. Serum laboratories included IGF-1 level 926 ng/mL, GH 2.17 ng/mL, prolactin 30.6 ng/mL, LH < 0.2 mIU/mL, FSH 1.2 mIU/mL, TSH 0.747 UIU/mL, free T4 0.7 ng/dL, and glucose 395 mg/dL. The patient was started on octreotide 100 μg subcutaneously every 8 hours. After 1 week of therapy, the patient had significantly improved visual acuity, improved visual fields, and decreased insulin requirement. Her IGF-1 level decreased by > 50% to 434 ng/mL. Repeat MRI revealed a decrease in size of the adenoma and no compression of the optic chiasm. This case illustrates an unusually rapid response of a somatotroph adenoma to octreotide. Thus, octreotide should be strongly considered in patients with an advanced tumor burden and in patients with compressive neurologic symptoms for whom urgent surgical intervention may be indicated. Response to the octreotide, as demonstrated by this case, may occur more quickly than previous studies have shown.
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