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The purpose of these studies are to evaluate the role of testosterone on autonomic and vascular function in men.
Sex hormones play a pivotal role in neurovascular function in humans. In recent years, great strides have been made in elucidating the roles of estrogen and progesterone on autonomic and vascular control in women; however, very little is known about the impact of testosterone in men. Given that low testosterone levels are associated with an increased risk of cardiovascular disease, reduced exercise capacity and vascular dysfunction, it is evident that testosterone plays a pivotal role in autonomic and vascular function in men. Our current understanding of testosterone's effects on neurovascular control are confounded by numerous factors that independently alter autonomic and vascular function such as aging and chronic disease (e.g. cardiovascular disease, metabolic disease). The purpose of these studies are to evaluate the role of testosterone on autonomic and vascular function in young men to better isolate the effects of testosterone from the aforementioned confounding factors. The outcomes of these studies will provide novel information regarding the role of male sex hormones in autonomic and vascular control, and further our understanding of the influence of sex hormones on human physiology.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| GnRH antagonist alone | Experimental | Intervention: Cetrorelix acetate (Cetrotide) |
|
| GnRH antagonist + Testosterone add-back | Experimental | Intervention: Cetrorelix acetate (Cetrotide) + Testosterone gel (Androgel) |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Cetrorelix Acetate | Drug | GnRH antagonist - subcutaneous injection. Day 1: 1-3 mg; Days 2-14: 0.25mg/daily. |
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| Measure | Description | Time Frame |
|---|---|---|
| Muscle sympathetic nerve activity | Multi-unit postganglionic muscle sympathetic nerve activity (MSNA) will be measured by inserting a unipolar tungsten microelectrode into the peroneal nerve near the fibular head of the leg. Neural signals will be amplified, filtered (bandwidth, 700-2,000 Hz), rectified, and integrated (time constant, 0.1 s) to obtain mean voltage neurograms. MSNA will be measured during both trials to evaluate the effect of testosterone on sympathetic activity directed toward the musculature. | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone |
| Endothelial function | Brachial artery flow-mediated dilation (FMD). Brachial artery FMD measures will be performed non-invasively via Doppler ultrasound. | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone |
| Forearm blood flow | Forearm blood flow will be measured using Doppler ultrasound at baseline and during stress (e.g. exercise) | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone |
| Measure | Description | Time Frame |
|---|---|---|
| Skeletal muscle microvascular blood flow | Microvascular blood flow will be measured using Diffuse correlation spectroscopy. | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone |
| Measure | Description | Time Frame |
|---|---|---|
| Sex hormones | Serum concentrations of total testosterone, estradiol, albumin, and sex hormone binding globulin (SHBG) will be measured to document changes in hormone concentrations. Free testosterone will be calculated using total testosterone, SHBG and albumin. | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone |
Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Andrew D'Souza, MSc | Contact | 519-661-2111 | 88084 | adsouz58@uwo.ca |
| Arlene Fleischhauer, RN | Contact | afleisc@uwo.ca |
| Name | Affiliation | Role |
|---|---|---|
| Joel K Shoemaker, Ph.D. | University of Western Ontario, Canada | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| the University of Western Ontario | London | Ontario | N6A 5B9 | Canada |
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| ID | Term |
|---|---|
| C062876 | cetrorelix |
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| Testosterone gel | Drug | Testosterone gel - transdermal application of 5mg/day on Day 7-14 of GnRH antagonist |
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