Healthy
Conditions
Brief summary
The purpose of these studies are to evaluate the role of testosterone on autonomic and vascular function in men.
Detailed description
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.
Interventions
GnRH antagonist - subcutaneous injection. Day 1: 1-3 mg; Days 2-14: 0.25mg/daily.
DRUGTestosterone gel
Testosterone gel - transdermal application of 5mg/day on Day 7-14 of GnRH antagonist
Sponsors
Western University, Canada
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
MALE
Age
18 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
* Moderately active * Free of chronic disease
Exclusion criteria
* congenital or acquired hypogonadism * drug/alcohol dependence * hypertension * current smoker * current opioid or cannabis user * diabetes * inability to provide written consent * parkinson's disease * cardiovascular disease * testosterone use within the last year
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Muscle sympathetic nerve activity | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone | 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. |
| Endothelial function | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone | Brachial artery flow-mediated dilation (FMD). Brachial artery FMD measures will be performed non-invasively via Doppler ultrasound. |
| Forearm blood flow | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone | Forearm blood flow will be measured using Doppler ultrasound at baseline and during stress (e.g. exercise) |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Skeletal muscle microvascular blood flow | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone | Microvascular blood flow will be measured using Diffuse correlation spectroscopy. |
Other
| Measure | Time frame | Description |
|---|---|---|
| Sex hormones | After 7 days GnRH antagonist alone and 7 days GnRH antagonist + Testosterone | 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. |
Countries
Canada
Contacts
Primary ContactAndrew D'Souza, MSc
Backup ContactArlene Fleischhauer, RN
Outcome results
None listed