BACKGROUND Testosterone levels decline as men age, as does cognitive function. Whether there is more than a temporal relationship between testosterone and cognitive function is unclear. Chemical castration studies in men with prostate cancer suggest that low serum testosterone may be associated with cognitive dysfunction. Low testosterone levels have also been observed in patients with Alzheime...

Previous investigations suggest that male tropical birds have lower plasma testosterone concentrations than northern latitude species. To test whether this generalization is valid, we analyzed all currently available plasma testosterone data of tropical birds. We focused on peak breeding testosterone levels using phylogenetic and conventional statistics. Explanatory variables considered were so...

Testosterone substitution is reported to produce a wide range of benefits for men with hypogonadism that include improvements in muscle mass, body composition, mood, bone density, libido, and cognition. Understanding the actions of exogenous testosterone on the prostate gland is important since testosterone is the major regulator of growth and function of this organ. To date, clinical studies o...

Testosterone is thought to be positively associated with "mating effort", or the initiation and establishment of sexual relationships (Wingfield et al., 1990). Yet, because testosterone is negatively associated with nurturance (van Anders et al., 2011), high levels of testosterone may be incompatible with relationship maintenance. For instance, partnered men with high testosterone report lower ...

The physiological role of multidrug resistance protein 4 (Mrp4, Abcc4) in the testes is unknown. We found that Mrp4 is expressed primarily in mouse and human Leydig cells; however, there is no current evidence that Mrp4 regulates testosterone production. We investigated its role in Leydig cells, where testosterone production is regulated by cAMP, an intracellular messenger formed when the lutei...

Preparation, evaluation and optimization of testosterone radioimmunoassay (RIA) system using liquid phase double antibody is considered to be the main objective. Three primary components were prepared and characterized to obtain valid and accurate system. These components were polyclonal testosterone antibody, the I-testosterone tracer and set of testosterone standards. The production of polycl...

This article is an adaptation of an abstract/poster presentaton made at the 13th International Congress on Steroidal Hormones and Hormones and Cancer, Quebec City, Canada (September 2008), concerning the topic of breast feeding as a contraindication to testosterone therapy. The purpose of the presentation and this article is to provide a summary of the findings of a study that was conducted to ...

Decreased testosterone levels in men are often a normal sign of aging. Testosterone replacement therapy (TRT) is a well-established option for those with symptomatic hypogonadism related to low testosterone levels. Conversely, designer herbal supplements in the context of testosterone supplementation are poorly studied, yet remain popular among aging men who seek the well-known, often enhancing...

OBJECTIVE Testosterone therapy increases lean body mass and decreases total fat mass in aging men with low normal testosterone levels. The major challenge is, however, to determine whether the metabolic consequences of testosterone therapy are overall positive. We have previously reported that 6-month testosterone therapy did not improve insulin sensitivity. We investigated the effect of testos...

Testosterone has been hypothesized to modulate the trade-off between mating and parenting effort in males. Indeed, evidence from humans and other pair-bonded species suggests that fathers and men in committed relationships have lower testosterone levels than single men and men with no children. To date, only one published study has examined testosterone in relation to motherhood, finding that m...