Abstract: Elderly men often show a concurrence of a decline of testosterone with attributes of the metabolic syndrome. This study tested the effects of normalization of testosterone.: A total of 122 hypogonadal men (18–83 years, mean 59.6±8.0 years; n=11<45 years, n=25<55 years, n=53<65 years) were included in the study. Their baseline testosterone levels were between 0.14 and 4.51 ng/mL (n>4.90 ng/mL) and were treated with parenteral testosterone undecanoate for 2 years as the sole

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... (administration at 0 and 6 weeks, and thereafter every 12 weeks).: Plasma testosterone increased from 3.3±1.9 ng/mL to 4.1±1.5 ng/mL (p<0.01) at 3 months, and then stabilized at 6.8±1.3 ng/mL after the first 6 months. There was a remarkable progressive linear decline in body weight, body mass index, and waist circumference over the entire study period. Plasma cholesterol decreased significantly over the first 12 months, and then stabilized. Plasma glucose, triglycerides, low-density lipoprotein cholesterol, and C-reactive protein decreased significantly and high-density lipoprotein cholesterol increased significantly over the 24-month study period in a non-linear manner. There was a significant decrease in aspartate aminotransferase and alanine aminotransferase levels over the first 9 and 12 months, and then values leveled off. Changes in variables were largely correlated with changes in testosterone levels. At baseline, 47 out of 122 subjects fulfilled the metabolic syndrome criteria as defined by the National Cholesterol Education Program (2001); after 2 years of testosterone treatment, this number had declined to 11 out of 122 subjects.: With testosterone treatment over 2 years, the most significant improvement of the metabolic syndrome was noted over the first 12 months, but over the following 12 months further improvement was also observed. With regard to safety of testosterone administration to mainly elderly men, a number of safety measures were carried out.