The purpose of the Nebido® publications portal (NPP) is to present testosterone related research, in an easily searchable and navigable interface, to health professionals who search for scientific information on hypogonadism, testosterone replacement therapy and testosterone related health issues.
Am J Physiol Endocrinol Metab. 2002 Mar;282(3):E601-7
Testosterone administration to men >60 years with baseline testosterone levels of <17 nmol/l (480 ng/dl) for 6 months increases total and leg lean body mass, muscle volume, and leg and arm muscle strength. Increases in lean body mass resulted from an increase in muscle protein net balance, due to a decrease in muscle protein breakdown.
Testosterone administration increases expression of both androgen receptor and IGF-I protein in muscle. The increased androgen receptor expression may be temporary or required dose escalation in order to not return to baseline levels.
J Gerontol A Biol Sci Med Sci. 2001 May;56(5):M266-72
Testosterone replacement therapy with transdermal testosterone in men aged 65-87 years with low bioavailable testosterone levels <4.44 nmol/L prevents bone loss, decreases body fat, and increases lean body mass.
A modest increase in PSA levels were seen, but no change in signs or symptoms of prostate hyperplasia.
Testosterone replacement therapy with transdermal gel reduces reduction fat mass and percent body fat, while improving sexual function and mood, and increased lean body mass and muscle strength. There were no significant changes in the lipid profile.
As anticipated, hematocrit and hemoglobin increases, but still within the normal range. The increase in mean serum prostate-specific antigen levels (within the normal range) was correlated with the increase in serum testosterone levels. Transdermal gel was better tolerated than patch, and in contrast to patch treatment, resulted in reduction fat mass and percent fat.
Testosterone replacement therapy for up to 3 years safely increases bone mineral density and fat-free mass, with no detrimental effects on lipids, hematocrit or prostate volume. This study shows that there is an initial elevation in safety parameters like hematocrit and prostate volume, from sub-normal to normal, after which they stabilize.
Improvements in self-reported sexual function and sense of energy occur relatively soon within the first 3 months of treatment.
Treatment of middle-aged men with abdominal obesity with transdermal testosterone for 9 months decreased visceral fat mass (measured by CT-scan), increased insulin sensitivity (measured with the euglycemic glucose clamp), decrease in fasting blood glucose, plasma cholesterol and triglycerides as well as diastolic blood pressure. Treatment with DHT increased visceral mass was detected. No other changes were found in the DHT and P groups.
Testosterone therapy in abdominally obese men results in general metabolic and circulatory improvements. There were no detectable changes in prostate volume (measured by ultra-sound), prostate specific antigen concentration, genito-urinary history or urinary flow measurements in any of the groups.
Visceral obesity in men is characterized by low testosterone (T) and insulin-like growth factor I (IGF-I) concentrations, the latter suggesting a relative growth hormone (GH) deficiency. Testosterone therapy in visceral obese men elevates IGF-I levels and improves blood glucose, chlolesterol and triglycerides and diastolic blood pressure.
It is suggested that IGF-I elevation with testosterone therapy might be due either to minor, non-detectable increases in GH secretion, or to direct effects of T on IGF-I concentrations. The mechanisms by which T-administration are leading to metabolic and anthropometric improvements, might be direct effects of T, with or without mediation via GH secretion.