Cardiac Function in GHR–/– Mice

The studies discussed in this chapter highlighted the role of GH signaling in heart function, cardiovascular disease, and glucose homeostasis. Interestingly, GHR−/− mice do not present major cardiovascular abnormalities, and their overall cardiovascular risk seems to be diminished, independently of their age and/or gender. Thus, the extended longevity of GHR−/− mice may be due in part to their improved cardiovascular health and increased insulin sensitivity. Although important aspects of GH signaling and the cardiovascular system have been revealed, the underlying mechanisms linking GH insensitivity and cardiovascular health/disease need to be investigated further. In a recent study, the effects of GH in coagulation or thrombosis were evaluated in a model of pulmonary embolism. Expression of coagulation inhibitors was strongly modulated by sex-specific GH secretion patterns (Wong et al. 2008).This study highlights the significance of GH on thrombosis in vivo and raises interesting questions. What are the specific effects of reduced IGF-1 vs. increased GH on thrombotic events? Thus, the thrombotic evaluation of GHR−/− mice will aid in redefining the role of GH/IGF-1 in thrombosis-related diseases.