Does Growth Hormone Cause Cancer?

P. J. Jenkins; A. Mukherjee; S. M. Shalet

Disclosures

Clin Endocrinol. 2006;64(2):115-121. 

In This Article

Acromegaly

One of the more controversial issues in the GH and cancer debate is that which relates to cancer risk in patients with acromegaly. Several retrospective studies have reported a variety of cancers in these patients (reviewed in reference 41), although others suggest the risk is actually lower than would be expected within the general population.[42,43] However, older reviews are limited by the use of mortality data from more than 50 years ago and will not reflect the current morbidity of patients with acromegaly that have been subjected to modern therapeutic strategies. Regardless, there appears to be general consensus that these patients are at increased risk of colorectal cancer, although there is on-going debate as to the exact extent of this risk. A summary of 14 prospective colonoscopic screening studies, involving more than 800 patients, suggests a 7·6-fold increased risk of colorectal cancer, compared to matched control subjects.[41] Other workers suggest the risk is considerably lower at approximately twofold.[42]

The risk of premalignant colonic adenomas is also controversial. The majority of clinical observations demonstrate an increased prevalence and suggest that these colonic adenomas behave more aggressively with an increased tendency for malignant progression,[44] but Renehan et al., using other control groups, made a case that adenoma prevalence rates were not increased.[45] Importantly, the relation of this neoplasia to IGF-1 was clarified by a prospective study involving a second colonoscopic evaluation of more than 100 patients at intervals after the original screening examination, when all visible polyps had been removed.[46] The occurrence of new adenomas was significantly related to both serum GH and IGF-1 levels and patients who had IGF-1 levels above the normal range had a 4·5-fold increased risk of developing a new adenoma compared to patients in whom disease activity was controlled. Previous work has also shown the colonic epithelium of patients with acromegaly to be characterized by increased proliferation, which is proportional to serum IGF-1 levels.[47]

Whether the prevalence of other cancers in acromegaly is increased remains unproven. Orme et al. reported the mortality from breast cancer to be increased, although this did not reach statistical significance[48] and an early retrospective review suggested the incidence but not mortality from this disease was increased fourfold.[49] The rarity of this condition and the consequent small number of patients in these studies makes it difficult to determine the true incidence of cancer in acromegaly.

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