Objective: The association between testosterone replacement therapy and cardiovascular risk remains controversial. Blood viscosity is a known individual risk factor for cardiovascular disease mortality. The objective of the present study was to investigate the effects of the long-acting injectable testosterone undecanoate (TU) on risk factors of cardiovascular disease. Methods: In total, 24 male New Zealand white rabbits (2.5 kg) were randomly divided into 3 groups of 8. Group 1 was used as control. Group 2 was castrated bilaterally and Group 3 was administrated with 6 mg/kg of TU at day 1 and 6 weeks after castration. Whole blood viscosity, total plasma testosterone, hemoglobin (Hb), hematocrit (Hct), fibrinogen (FBN), total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels were measured at baseline, 6 weeks and 18 weeks. Results: In the control group, whole blood viscosity and FBN were significantly increased at 6 and 18 weeks. Castration significantly increased the levels of TC, TG, HDL-C and LDL-C, but decreased Hct and Hb. In the TU injection group, whole blood viscosity was markedly decreased in all share rates, whereas the FBN level was increased. Hb and Hct showed a tendency for higher concentration at 6 weeks. Conclusions: Long-acting injectable TU provides another reliable treatment option for testosterone replacement therapy. Moreover, the patients may receive additional beneficial effect in lowered whole blood viscosity.
IntroductionTestosterone plays a crucial role in the proper development of male reproductive tissues and in the maintenance of male characteristics.1 Testosterone levels decline gradually with age, and testosterone deficiency can cause significant morbidity and substantial reduction in quality of life.Male hypogonadism, affecting about 30% of men between the ages of 40 and 79 years, 2 is a clinical condition in which abnormally low serum testosterone levels are found associated with typical symptoms, including diminished libido and sense of vitality, erectile dysfunction, reduced muscle mass and bone density, depression and anemia.3 Although many of these symptoms can be relieved by restoring serum testosterone levels to the normal range, there is considerable controversy about the potential risks of testosterone replacement therapy.An increasing incidence of hematopoietic disorders is a risk of testosterone use. Testosterone increases erythropoietin production by hypertrophy of renal tissue, particularly in high doses. 4 Activation of androgen receptors in erythroid cells appears to be necessary for testosterone to develop an erythropoietic effect in the bone marrow.5 Drastic elevations of hematocrit (Hct) may be detrimental to patients with underlying coronary, cerebral or peripheral vascular disease by possibly causing an increase in blood viscosity and increased risk of thrombosis.6-8 However, no causal relation has been found between higher testosterone levels and cardiovascular diseas...