It is now known that BNP and NT-proBNP levels are decreasing with increased BMI, regardless of other metabolic syndrome (MS) constituents. Additionally, testosterone deficiency may intensify frequency of ventricular rhythm disorders in obese individuals by inhibition of the parasympathetic system. Determination of heart rhythm turbulence (HRT) is a useful, noninvasive method used for evaluation of equilibrium of the vegetative system. The aim of the study was to evaluate effect of testosterone therapy on HRT and NT-proBNP levels in MS patients. Eighty males were qualified for the study. They were divided into 3 groups: I (n=30), males with testosterone deficiency syndrome and metabolic syndrome (MS+TDS+); II (n=25), males with MS+TDS-; III (n=25), healthy males. The patients with MS+TDS+ received Omnadrem 250 in the form of intramuscular injections for 9 weeks. Laboratory tests and 24-h Holter ECG were taken twice before the therapy and directly after completion of the therapy. Males with MS+TDS+ more often presented irregular HRT parameters and were characterised by lower NT-proBNP levels compared to the healthy individuals. Testosterone replacement therapy caused improvement of HRT and had no significant effect on the NT-proBNP level. Testosterone replacement therapy and body weight reduction may significantly decrease negative consequences of MS and TDS.