To the Editor: Vance's discussion of growth hormone (Feb. 27issue)1 omits important reports in the literature. The combinationof growth hormone and exercise (unlike exercise alone) has beenshown to increase type II muscle fibers in the elderly2 —an important finding, since frailty and sarcopenia are predominantlyrelated to the loss of type II fibers. There is no mention ofthe fact that decreased levels of insulin-like growth factorI have been reported to be associated with angina pectoris,3myocardial infarction,4 and atherosclerosis,5 which are theleading causes of death in this country. The discussion alsoexcludes a recent report that aging men with low levels of insulin-likegrowth factor I die earlier than those with high levels.6
Long-term prospective studies on the potential of growth hormonewill take decades. In the meantime, the use of growth hormoneshould be based on a patient's clinical status and on a candidpatient–physician discussion of current information onthe pros and cons of such therapy.
Khalid Mahmud, M.D. North Memorial Medical Center Minneapolis, MN 55422 kmahmud{at}idinhealth.com
References
Vance ML. Can growth hormone prevent aging? N Engl J Med 2003;348:779-780. [Free Full Text]
Hennessey JV, Chromiak JA, DellaVentura S, et al. Growth hormone administration and exercise effects on muscle fiber type and diameter in moderately frail older people. J Am Geriatr Soc 2001;49:852-858. [CrossRef][Web of Science][Medline]
Conti E, Andreotti F, Sestito A, et al. Reduced levels of insulin-like growth factor-1 in patients with angina pectoris, positive exercise stress test, and angiographically normal epicardial coronary arteries. Am J Cardiol 2002;89:973-975. [CrossRef][Web of Science][Medline]
Conti E, Andreotti F, Sciahbasi A, et al. Markedly reduced insulin-like growth factor-1 in the acute phase of myocardial infarction. J Am Coll Cardiol 2001;38:26-32. [Free Full Text]
van den Beld AW, Bots ML, Janssen JA, Pols HA, Lamberts SW, Grobbee DE. Endogenous hormones and carotid atherosclerosis in elderly men. Am J Epidemiol 2003;157:25-31. [Free Full Text]
Ruiz-Torres A, Soares de Melo Kirzner M. Ageing and longevity are related to growth hormone/insulin like growth factor-1 secretion. Gerontology 2002;48:401-407. [CrossRef][Medline]
Dr. Vance replies: Dr. Mahmud correctly notes that the combinationof growth hormone and exercise increases type II muscle fibersin the elderly. As stated in my Retrospective article, changesin body composition with growth hormone administration do notimprove function in the elderly. Reduced levels of insulin-likegrowth factor I may be associated with other diseases, althoughsuch an association is not proof of cause and effect and mayecho the effect of disease; for example, insulin-like growthfactor I may be low in young women with anorexia nervosa.1 Thatolder men with low levels of insulin-like growth factor I maydie earlier than those with high levels may reflect underlyingdiseases. Rudman et al. reported that elderly men living independentlyhad higher levels of insulin-like growth factor I than thoseliving in a nursing home and had fewer medical problems.2 Again,these associations are valid but do not demonstrate cause andeffect.
"Long-term prospective studies on the potential of growth hormonewill take decades": I agree. Without such studies, anyone caneasily fall prey to unproven claims. Recall laetrile for cancer:How many people "believed" that it was efficacious? How manydid not receive appropriate therapies, in the quest for a "magicbullet"? Appropriate studies, not opinions, are the only wayto determine whether a treatment is beneficial.
Mary Lee Vance, M.D. University of Virginia Medical Center Charlottesville, VA 22908 mlv{at}virginia.edu
Editor's note: Dr. Vance has reported receiving grant supportand consulting fees from Pharmacia and grant support from EliLilly and Genentech.
References
Caregaro L, Favaro A, Santonastaso P, et al. Insulin-like growth factor 1 (IGF-1), a nutritional marker in patients with eating disorders. Clin Nutr 2001;20:251-257. [CrossRef][Medline]
Rudman D, Nagraj HS, Mattson DE, et al. Hyposomatomedinemia in the men of a Veterans Administration nursing home: prevalence and correlates. Gerontology 1987;33:307-314. [Medline]
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