Some elucidation of the mechanisms of vascular disease in hypopituitarism

Growth hormone (GH) treatment does not restore endothelial function in children with GH deficiency

BACKGROUND

In adults with growth hormone (GH) deficiency (GHD), GH treatment restores impaired endothelial function, a precursor of cardiovascular disease. Its effect in children with GHD is unknown.

METHODS

Three months of GH (0.3 mg/kg/wk) were given to nine children with GHD. Endothelial function was measured via reactive hyperemic response. Forearm blood flow (FBF, strain gauge plethysmography) was measured before and after 5 min of upper arm arterial occlusion. Blood pressure and lipid, insulin and glucose levels were measured. Pretreatment endothelial function was compared to 18 previously studied control children.

RESULTS

Percent fall in forearm vascular resistance was greater in controls (81.2 +/- 1.9%) than in children with GHD (69.6 +/- 5.3%, p = 0.021) but was not affected by GH (60.6 +/- 7.5%). GH markedly increased HOMAIR (21 +/- 7 versus 43 +/- 8, p = 0.004). Plasma lipid levels did not significantly differ.

CONCLUSION

These results indicate that endothelial function is impaired in children with GHD. GH therapy does not restore the impairment.

Cardiovascular risk in patients with growth hormone deficiency: effects of growth hormone substitution

OBJECTIVE

To review the literature on the increased cardiovascular risk in patients with growth hormone (GH) deficiency and the positive effects of GH replacement.

METHODS

We analyze the factors that contribute to cardiovascular risk in GH deficiency, including body composition and lipid profile, and summarize GH treatment strategies and results described in the literature.

RESULTS

The prominent clinical finding in patients with GH deficiency is the increased abdominal fat, even in patients with normal weight. Cardiac ejection volume tends to be decreased, and arterial distensibility is diminished. The lipid status is also worsened, accompanied by increased inflammatory markers, such as highly sensitive C-reactive protein. Typically, GH treatment reduces visceral fat and increases muscle mass, changes that diminish cardiovascular risk. Because of direct effects as well as increased hemodynamic performance and increased blood volume, cardiac performance is improved. With GH therapy, total cholesterol and low-density lipoprotein levels decrease by 10% to 20%, and inflammatory markers such as C-reactive protein decline. Carbohydrate metabolism during moderate to long-term treatment is minimally affected, although obese patients with GH deficiency on rare occasion may have hyperglycemia or even diabetes.

CONCLUSION

The relevance of the beneficial effects of GH on the cardiovascular system is strongly suggested but not fully proved. The results in a large cohort of GH-treated patients (the KIMS or Pharmacia and Upjohn International Metabolic Surveillance database) demonstrated no difference in cardiovascular risk in comparison with that in a control population after a mean of 3 years of treatment.