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Reductions In Serum Igf-1 During Aging Impair Health Span, Zhenwei Gong, Oran Kennedy, Hui Sun, Yingjie Wu, Garry A. Williams, Laura Klein, Luis Cardoso, Ronald W. Matheny Jr, Gene B. Hubbard, Yuji Ikeno, Roger P. Farrar, Mitchell B. Schaffler, Martin L. Adamo, Radhika H. Muzumdar, Shoshana Yakar

Publications and Research

In lower or simple species, such as worms and flies, disruption of the insulin-like growth factor (IGF)-1 and the insulin signaling pathways has been shown to increase lifespan. In rodents, however, growth hormone (GH) regulates IGF-1 levels in serum and tissues and can modulate lifespan via/or independent of IGF- 1. Rodent models, where the GH/IGF-1 axis was ablated congenitally, show increased lifespan. However, in contrast to rodents where serum IGF-1 levels are high throughout life, in humans, serum IGF-1 peaks during puberty and declines thereafter during aging. Thus, animal models with congenital disruption of the GH/ IGF-1 axis are unable …

Testosterone, Cardiovascular, Men, Trial, Lin Xu, Guy Freeman, Benjamin J. Cowling, Mary Schooling

Publications and Research

Background
Testosterone therapy is increasingly promoted. No randomized placebo-controlled trial has been implemented to assess the effect of testosterone therapy on cardiovascular events, although very high levels of androgens are thought to promote cardiovascular disease.

Methods
A systematic review and meta-analysis was conducted of placebo-controlled randomized trials of testosterone therapy among men lasting 12+ weeks reporting cardiovascular-related events. We searched PubMed through the end of 2012 using “(“testosterone” or “androgen”) and trial and (“random*”)” with the selection limited to studies of men in English, supplemented by a bibliographic search of the World Health Organization trial registry. Two reviewers independently searched, …

The Effect Of Statins On Testosterone In Men And Women, A Systematic Review And Meta-Analysis Of Randomized Controlled Trials, Mary Schooling, Shiu Lun Au Yeung, Guy Freeman, Benjamin J. Cowling

Publications and Research

Background
Statins are extensively used for cardiovascular disease prevention. Statins reduce mortality rates morethan other lipid-modulating drugs, although evidence from randomized controlled trials also suggests that statinsunexpectedly increase the risk of diabetes and improve immune function. Physiologically, statins would beexpected to lower androgens because statins inhibit production of the substrate for the local synthesis of androgens and statins’ pleiotropic effects are somewhat similar to the physiological effects of lowering testosterone, so we hypothesized that statins lower testosterone.

Methods
A meta-analysis of placebo-controlled randomized trials of statins to test the a priori hypothesis that statins lower testosterone. We searched the PubMed, …