eMedicine Specialties > Endocrinology > Pituitary Gland

Acromegaly: Differential Diagnoses & Workup

Author: Hasnain M Khandwala, MD, FRCPC, Endocrinologist, LMC Endocrinology Centers, Canada
Contributor Information and Disclosures

Updated: Feb 13, 2009

Differential Diagnoses

Other Problems to Be Considered

Pseudoacromegaly

Workup

Laboratory Studies

  • Random GH measurements are often not diagnostic because of the episodic secretion of GH, its short half-life, and the overlap between GH concentration in acromegalic patients and healthy subjects.
  • Because GH secretion is inhibited by glucose, measurement of glucose nonsuppressibility might be useful. Two baseline GH levels are obtained prior to ingestion of 75 or 100 g of oral glucose, and additional GH measurements are made at 30, 60, 90, and 120 minutes following the oral glucose load.
    • Patients with active acromegaly are unable to suppress GH concentration below 2 ng/mL after a 75-g oral glucose load. With newer assays for GH using the immunoradiometric assay (IRMA), a criterion of less than 1 mcg/L is used following oral glucose ingestion.
    • A paradoxical rise in GH concentration is observed in 15-20% of patients with acromegaly following oral glucose ingestion.
  • Because IGF-I has a long half-life, its measurement is useful to gauge integrated GH secretion, to screen for acromegaly, and to monitor the efficacy of therapy.
    • IGF-I concentrations vary with age. An assay in which reference ranges have been stratified in such a manner is required.
    • Starvation, obesity, and diabetes mellitus decrease IGF-I concentration.
    • Pregnancy increases IGF-I concentration.
  • Measurement of IGF-binding protein-3 (IGFBP-3), the main binding protein for circulating IGF, is increased in acromegaly and might be useful in the diagnosis of acromegaly. Measurement may also be helpful in following the activity of the disease during treatment.
  • GHRH concentration can be obtained if clinically indicated.
    • Levels of less than 300 pg/mL usually indicate an ectopic source of GHRH.
    • In pituitary disease (GHRH independent), GHRH concentration is within reference ranges or suppressed.
  • Because up to 20% of GH-secreting pituitary adenomas cosecrete prolactin, the prolactin level may also be elevated. However, as indicated above, a rise in prolactin can be due to stalk compression as well as co-secretion from a pituitary adenoma.
  • Pituitary adenomas can be associated with deficiencies of other pituitary hormones. Consider evaluation of the adrenal, thyroid, and gonadal axes.

Imaging Studies

  • Because of the relatively high incidence of nonfunctioning, incidentally discovered pituitary adenomas, obtain imaging studies only after a firm biochemical diagnosis of acromegaly.
  • Because GH-secreting pituitary adenoma is the most common cause, perform imaging of the sella turcica first.
    • MRI is more sensitive than CT scan.
    • MRI provides detailed information about surrounding structures such as the optic chiasm and cavernous sinuses.
  • If the MRI findings of the sella are negative, appropriate studies to localize tumors causing ectopic secretion of GH or GHRH can be obtained.
    • CT scan of the abdomen/pelvis evaluates for pancreatic, adrenal, or ovarian tumors secreting GH/GHRH.
    • Chest CT scanning evaluates for bronchogenic carcinoma secreting GH/GHRH.

More on Acromegaly

Overview: Acromegaly
Differential Diagnoses & Workup: Acromegaly
Treatment & Medication: Acromegaly
Follow-up: Acromegaly
References
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References

  1. Asa SL. The pathology of pituitary tumors. Endocrinol Metab Clin North Am. 28(1):13-43, v-vi. [Medline].

  2. Bates AS, Van't Hoff W, Jones JM, et al. An audit of outcome of treatment in acromegaly. Q J Med. May 1993;86(5):293-9. [Medline].

  3. Ezzat S. Acromegaly. Endocrinol Metab Clin North Am. Dec 1997;26(4):703-23. [Medline].

  4. Feenstra J, de Herder WW, ten Have SM, et al. Combined therapy with somatostatin analogues and weekly pegvisomant in active acromegaly. Lancet. May 7-13 2005;365(9471):1644-6. [Medline].

  5. Freda PU. Current concepts in the biochemical assessment of the patient with acromegaly. Growth Horm IGF Res. Aug 2003;13(4):171-84. [Medline].

  6. Freda PU, Wardlaw SL, Post KD. Long-term endocrinological follow-up evaluation in 115 patients who underwent transsphenoidal surgery for acromegaly. J Neurosurg. Sep 1998;89(3):353-8. [Medline].

  7. Gagel RF, McCutcheon IE. Images in clinical medicine. Pituitary gigantism. N Engl J Med. Feb 18 1999;340(7):524. [Medline].

  8. McCutcheon IE. Management of individual tumor syndromes. Pituitary neoplasia. Endocrinol Metab Clin North Am. Mar 1994;23(1):37-51. [Medline].

  9. Melmed S, Ho K, Klibanski A, et al. Clinical review 75: Recent advances in pathogenesis, diagnosis, and management of acromegaly. J Clin Endocrinol Metab. Dec 1995;80(12):3395-402. [Medline].

  10. Melmed S, Jackson I, Kleinberg D, Klibanski A. Current treatment guidelines for acromegaly. J Clin Endocrinol Metab. Aug 1998;83(8):2646-52. [Medline].

  11. Newman CB. Medical therapy for acromegaly. Endocrinol Metab Clin North Am. Mar 1999;28(1):171-90. [Medline].

  12. Newman CB, Melmed S, George A, et al. Octreotide as primary therapy for acromegaly. J Clin Endocrinol Metab. Sep 1998;83(9):3034-40. [Medline].

  13. Paisley AN, Trainer PJ. Medical treatment in acromegaly. Curr Opin Pharmacol. Dec 2003;3(6):672-7. [Medline].

  14. Rajasoorya C, Holdaway IM, Wrightson P, et al. Determinants of clinical outcome and survival in acromegaly. Clin Endocrinol (Oxf). Jul 1994;41(1):95-102. [Medline].

  15. Spada A, Vallar L. G-protein oncogenes in acromegaly. Horm Res. 1992;38(1-2):90-3. [Medline].

  16. Thorner M, Vance ML, Laws E. The anterior pituitary. In: Wilson JD, ed. Williams Textbook of Endocrinology. 9th ed. Philadelphia, Pa: Saunders; 1998:249-340.

  17. Trainer PJ, Drake WM, Katznelson L, et al. Treatment of acromegaly with the growth hormone-receptor antagonist pegvisomant. N Engl J Med. Apr 20 2000;342(16):1171-7. [Medline].

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Further Reading

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Keywords

growth hormone, GH, somatotroph tumor, growth hormone-releasing hormone, GHRH, insulinlike growth factor-I, IGF-I, somatomedin C, SM-C, guanosine triphosphate, GTP, glycogen synthetase phosphatase, GSP, acral overgrowth, macrognathia, visceral overgrowth, macroglossia, panhypopituitarism, somatic hypertrophy, hypertrophic arthropathy, kyphosis, hyperhidrosis, visceral hypersomia, multinodular goiter, colon polyposis, pseudoacromegaly, transsphenoidal hypophysectomy, somatostatin analogues, dopamine agonists, immunoradiometric assay, IRMA

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Contributor Information and Disclosures

Author

Hasnain M Khandwala, MD, FRCPC, Endocrinologist, LMC Endocrinology Centers, Canada
Hasnain M Khandwala, MD, FRCPC is a member of the following medical societies: American Association of Clinical Endocrinologists, American College of Physicians, American Diabetes Association, Canadian Medical Association, and Endocrine Society
Disclosure: Nothing to disclose.

Medical Editor

Barry J Goldstein, MD, PhD, Director, Division of Endocrinology, Diabetes and Metabolic Diseases, Professor, Department of Internal Medicine, Thomas Jefferson University
Barry J Goldstein, MD, PhD is a member of the following medical societies: Alpha Omega Alpha, American College of Clinical Endocrinologists, American College of Physicians-American Society of Internal Medicine, American Diabetes Association, and Endocrine Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Arthur B Chausmer, MD, PhD, FACP, FACE, FACN, CNS, Professor of Medicine (Endocrinology, Adj), Johns Hopkins School of Medicine; Affiliate Research Professor, Bioinformatics and Computational Biology Program, School of Computational Sciences, George Mason University; Principal, C/A Informatics, LLC
Arthur B Chausmer, MD, PhD, FACP, FACE, FACN, CNS is a member of the following medical societies: American Association of Clinical Endocrinologists, American College of Endocrinology, American College of Nutrition, American College of Physician Executives, American College of Physicians, American College of Physicians-American Society of Internal Medicine, American Medical Informatics Association, American Society for Bone and Mineral Research, American Society of Law Medicine and Ethics, Endocrine Society, and International Society for Clinical Densitometry
Disclosure: Nothing to disclose.

CME Editor

Mark Cooper, MBBS, PhD, FRACP, Head, Diabetes & Metabolism Division, Baker Heart Research Institute, Professor of Medicine, Monash University
Disclosure: Nothing to disclose.

Chief Editor

George T Griffing, MD, Professor of Medicine, St Louis University School of Medicine
George T Griffing, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Medical Practice Executives, American College of Physician Executives, American College of Physicians, American Diabetes Association, American Federation for Medical Research, American Heart Association, Central Society for Clinical Research, Endocrine Society, International Society for Clinical Densitometry, and Southern Society for Clinical Investigation
Disclosure: Nothing to disclose.

 
 
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