O 25. Role of testosterone on whole blood viscosity in rabbit

Introduction: The association between testosterone replacement therapy and cardiovascular risk remains unclear. Most recent reports suggest that low testosterone level is associated with increased male morbidity and mortality. The objective of the present study was to evaluate the effect of testosterone undecanoate (TU) in physiologic dose on blood hematocrit, haemoglobin, fibrinogen and viscosity.

Materials and Methods: Twenty four male New Zealand White rabbits (2-2.5 kg) were involved in this study, of which 16 underwent orchiectomy and the other 8 underwent a sham procedure. The 16 rabbits were randomly divided into 2 groups (8/group): Castrated group and castrated TU injection group. The 8 rabbits in TU injection group were administrated 6 mg/kg TU i.m at 1 day and 6 weeks after orchiectomy. The blood viscosity, testosterone, hematocrit, haemoglobin, blood chemistry and fibrinogen levels were measured at 0 week, 6 weeks and 18 weeks after orchiectomy.

Results: In control group, the blood viscosity, testosterone and fibrinogen levels were significantly increased at 6 and 18 weeks (P<0.01). In castrated group, the blood viscosity decreased and the fibrinogen level increased but without statistical significance compared with before orchiectomy. In TU injection group, the blood viscosity was significantly decreased compared with either before orchiectomy or control group (P<0.01), altogether the fibrinogen level significantly increased. In all groups, the hematocrit and haemoglobin had no significant difference.

Conclusions: The patients who received physiologic dose of TU may also have a beneficial effect in lowing cardiovascular risk. Further study is needed to find out the underlying mechanism.