Association of insulin resistance and nocturnal fall of blood pressure in GH-deficient adults during GH replacement

Growth hormone and the cardiovascular system

Growth hormone (GH) exerts its effects through insulin-like growth factor-1, and although ubiquitous in human tissues, it has a significant role in cardiovascular function. In recent years, there has been a great deal of interest in GH as an etiologic factor in many cardiovascular disease states. Acromegaly, a state of endogenous GH excess, results in myocardial hypertrophy and decreased cardiac performance with increased cardiovascular mortality. Additional insight into the role of excess GH on the cardiovascular system has been gained from data collected in athletes doping with GH. Likewise, GH deficiency is associated with increased mortality, possibly from the associated increase in atherosclerosis, lipid abnormalities, and endothelial dysfunction. However, further research is required to clarify the benefit of GH treatment in both deficient states and in heart failure patients.

Effects of 5 years of growth hormone (GH) replacement therapy on cardiac parameters and physical performance in adults with GH deficiency

The purpose of this study was to evaluate the effects of 5 years of GH substitution on cardiac structure and function, physical work capacity and blood pressure levels in adults with GH deficiency (GHD). Fourteen patients were clinically assessed every 3 months for 5 years. Transthoracic echocardiography and exercise test were performed at baseline, 24, 48 and 60 months. Blood pressure (BP) was measured by means of ambulatory monitoring of blood pressure at baseline, 6, 12, 24 and 60 months. Left ventricular mass and its index increased progressively during the 5 years of GH substitution (P = 0.008 and 0.007, respectively). There were no significant changes in all others cardiac parameters evaluated. It was observed a significant improve in functional capacity (P < 0.001) and maximal oxygen uptake (P = 0.006) during the treatment. Diurnal systolic BP increased by 15 mmHg (P = 0.024) and diurnal diastolic BP by 4.5 mmHg (P = 0.037). There was no change in dirnal systolic pressure load but a considerable but non-statistically significant reduction in diurnal diastolic pressure load was observed during the study. During the night diastolic BP increased by 4 mmHg (P = 0.012) despite a substantial but non-statistically significant reduction in diastolic pressure load. We observed an increase in the proportion of persons with a non-physiological nocturnal fall (non-dippers) throughout the study (from 36.4% at baseline to 54.6% after 60 months of therapy). We concluded that 5 years of GH replacement promoted positive effects on exercise capacity and maximum oxygen uptake in spite of a modest increase in BP levels and left ventricular mass. Continuous monitoring is mandatory to arrive at further conclusions concerning the effects of GH substitution in adults on cardiovascular parameters with respect to possible unfavorable long term effects.