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Mechanisms of Blood Pressure Dysfunction in Transmen Receiving Testosterone

Primary Purpose

Transgender Men, Blood Pressure, Hyperandrogenism

Status
Withdrawn
Phase
Not Applicable
Locations
Study Type
Interventional
Intervention
Trans men
Sponsored by
Yale University
About
Eligibility
Locations
Arms
Outcomes
Full info

About this trial

This is an interventional basic science trial for Transgender Men focused on measuring transgender, baroreflex, testosterone

Eligibility Criteria

18 Years - 45 Years (Adult)FemaleAccepts Healthy Volunteers

Inclusion Criteria:

  • Both groups (trans men and cisgender women) must be healthy and non-smoking. Control participants must be cisgender women with regular menses every 26-34 days. Trans men participants must be currently receiving testosterone for gender affirming hormone therapy where physiologic doses of exogenous Dihydrotestosterone have been administered (via injection or transdermal application) for at least 3 months as prescribed by their local endocrine provider as part of their clinically indicated hormone therapy. Doses can vary depending on the size and goals of each patient, but blood testosterone will be between 400-1000 ng/dl.

Exclusion Criteria:

  • Subjects who smoke, have diabetes, or BP>140/90 will be excluded.
  • Subjects will not be taking medications during the study, including any insulin-sensitizing or cardiovascular medications.
  • Subjects are excluded if they have lost > 5 kg of weight within the past 6 months or perform high-intensity exercise > 3 times/week.

Sites / Locations

    Arms of the Study

    Arm 1

    Arm 2

    Arm Type

    Active Comparator

    No Intervention

    Arm Label

    Trans men

    control

    Arm Description

    transgender men taking physiologic doses of testosterone for gender affirming hormone therapy

    cisgender women not receiving testosterone and with normal sex hormone levels

    Outcomes

    Primary Outcome Measures

    Muscle Sympathetic Nerve Activity (MSNA)
    MSNA is recorded continuously at rest and during O/LBNP protocols with a tungsten microelectrode (0.2 diameters insulated shaft tapered to an uninsulated tip of ~1-5 μm) inserted percutaneously into the median nerve. Multiunit, postganglionic MSNA is distinguished from other sources of nerve activity by the presence of spontaneous pulse synchronous bursts, increased activity when the subject holds their breath or clenches their first (stretches forearm muscles around median nerve), or if activity does not change when the skin is stimulated by light brushing or stroking (indicates lack of skin nerve activity). Bursts of MSNA at rest and during LBNP are quantified as total activity (AU/min), burst frequency (bursts/min) and burst incidence (bursts/100 heartbeats). The MSNA burst incidence is expressed in bursts/100 heartbeats to normalize for differences in heart rate among subjects.
    Systolic Blood Pressure (SBP)
    SBP is measured continuously with a Finometer beat-to-beat blood pressure measurement system at rest and during O/LBNP protocols. Units are mm Hg.
    Diastolic Blood Pressure (DBP)
    DBP is measured continuously with a Finometer beat-to-beat blood pressure measurement system at rest and during O/LBNP protocols. Units are mm Hg.
    Mean Arterial Pressure (MAP)
    MAP at rest and during O/LBNP protocols is calculated as 1/3(SBP-DBP)+DBP using the beat-to-beat SBP and DBP measurements taken with the Finometer system. Units are mm Hg.
    Sympathetic Baroreflex (BR) Gain
    Sympathetic BR gain is used as an index of sympathetic (neural) control of blood pressure, where gain is determined by the slope of the linear relationship between MSNA (burst/100 heartbeats) and DBP (mm Hg) at rest and during LBNP. The relationship produces a negative slope in that for a given subject, when DBP falls below the normal level sustained at rest, sympathetic activity increases to restore DBP back to that normal level. Thus, more MSNA bursts are observed at lower levels of DBP and vice versa. A steeper (more negative) slope suggests greater sensitivity of the baroreceptors to changes in blood pressure, and thereby more effective sympathetic control of blood pressure. A flatter slope suggests impaired BR sensitivity and blood pressure dysfunction, which is expected for the trans men group compared to cisgender women controls.
    Frequency in the Neural Cardiovascular Control
    The frequency of SBP, DBP and heart rate during OLBNP is analyzed in Matlab in a linear time-invariant system (LTI) framework. Heart rate and BP measures taken during OLBNP are low-pass filtered (0.05 Hz estimated example) and corrected for end-effects using a Hamming window. The derived impulse responses (IRs) are 1/3rd octave smoothed before calculating the frequency power spectra (0.001-0.05 Hz estimated example). The power of DBP and SBP at the OLBNP frequency are anticipated to be independently inversely related to the efficiency of BP control. Further, the difference in heart rate and SBP, and in heart rate and DBP, power at those frequencies reflects the degree of autonomic function, analogous to baroreflex gain.
    Electrocardiogram (ECG)
    A 3-lead ECG is continuously recorded at rest and during the O/LBNP protocols. The R-wave of the QRS complex of the ECG recording will be used for measures of pulse interval by determining the amount of time in seconds between the R-waves of 2 consecutive QRS complexes.

    Secondary Outcome Measures

    Brachial Artery Mean Blood Flow Velocity
    Mean blood flow velocity in the brachial artery will be examined at rest and during LBNP using Doppler ultrasound velocimetry. Blood flow velocity spectra and arterial diameter are measured simultaneously with a Doppler probe and SonoScape S2 ultrasound system. The brachial artery is imaged with a 6.0-MHz linear array probe positioned at a 45° angle over the skin at the distal one-third of the upper arm. Brachial blood flow is expected to decrease as the level of LBNP increases and induces a greater orthostatic challenge. For example, blood flow would be highest at the -10LBNP stage and continually decrease during the following stages of -20, -30 and finally -40LBNP, where blood flow would be the lowest.
    Cardiovagal Baroreflex (BR) Gain
    Cardiovagal BR gain is determined by the slope of the linear relationship between R-R Interval (seconds) and SBP (mm Hg) at rest and during LBNP. R-R Intervals are obtained from the ECG recording and SBP is obtained from the beat-to-beat measures taken by the Finometer.

    Full Information

    First Posted
    August 17, 2020
    Last Updated
    October 31, 2022
    Sponsor
    Yale University
    Collaborators
    The John B. Pierce Laboratory
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    1. Study Identification

    Unique Protocol Identification Number
    NCT04524325
    Brief Title
    Mechanisms of Blood Pressure Dysfunction in Transmen Receiving Testosterone
    Official Title
    Mechanisms of Blood Pressure Dysfunction in Transmen Receiving Testosterone
    Study Type
    Interventional

    2. Study Status

    Record Verification Date
    October 2022
    Overall Recruitment Status
    Withdrawn
    Why Stopped
    Funding never received.
    Study Start Date
    January 1, 2023 (Anticipated)
    Primary Completion Date
    July 1, 2023 (Anticipated)
    Study Completion Date
    June 30, 2024 (Anticipated)

    3. Sponsor/Collaborators

    Responsible Party, by Official Title
    Sponsor
    Name of the Sponsor
    Yale University
    Collaborators
    The John B. Pierce Laboratory

    4. Oversight

    Studies a U.S. FDA-regulated Drug Product
    No
    Studies a U.S. FDA-regulated Device Product
    No
    Data Monitoring Committee
    No

    5. Study Description

    Brief Summary
    The purpose of this research is to explore the effects of chronic androgen exposure on sympathetic nervous system activity (SNSA) and baroreflex control of blood pressure responses in transgender men (trans men) taking gender affirming hormone therapy (HT). Blood pressure, baroreflex gain, and frequency of sympathetic responses to changes in blood pressure will be assessed in trans men and a control group of cisgender women. To fully understand HT effects on blood pressure regulation in trans men, it is crucial to understand how both SNSA, and the pattern of SNSA, can be influenced by high levels of androgen exposure in the female cardiovascular system, as well as how the two regulatory components may interact.
    Detailed Description
    The purpose of this research is to study how testosterone affects blood pressure control in trans men. High testosterone levels are detrimental to the female cardiovascular system in that higher levels are associated with increased blood pressure. Humans control blood pressure in the autonomic nervous system via the baroreflex mechanism. The arterial baroreflex is a key autonomic homeostatic mechanism involved in maintaining arterial blood pressure, and gain of the baroreflex is used as a measure of the sensitivity of sympathetic responses that act to restore acute blood pressure fluctuations. This autonomic regulation of blood pressure is also characterized by rhythmic activity (changes in cardiac frequency), which can be observed by recording sympathetic nerve traffic. When the female cardiovascular system is exposed to elevated androgens, baroreflex gain is impaired, and blood control is less efficient during an orthostatic challenge. However, to best understand the effect of a given stimulus on autonomic function, changes in frequency of the SNSA response must also be quantified in addition to the gain. Sympathetic control of arterial blood pressure is most effective in a narrow frequency range, and if this frequency range for responsiveness should narrow further, control of arterial blood pressure becomes less efficient and presents as dysfunction. The central hypothesis for this research is that dysregulation of blood pressure in trans men taking testosterone for gender affirming HT is a function of both reduced baroreflex gain and narrowed frequency-dependent relationship between arterial pressure and peripheral sympathetic vascular responsiveness. Specifically, these studies test the hypothesis that androgen supplementation with HT is associated with 1) lower baroreflex gain during a lower body negative pressure (LBNP) challenge, and 2) a narrowed response frequency range that precedes impaired sympathetic vascular response dynamics in trans men compared to control cisgender women. Study procedures include an oral glucose tolerance test (OGTT), microneurography of the median nerve in the forearm to assess SNSA, and 2 LBNP challenges designed to examine baroreflex gain during static LBNP and then the frequency of SNSA during oscillating LBNP (OLBNP). Participants complete 3 visits for this study. Visit 1 is for informed consent procedures; Visit 2 is a pre-screening visit to complete the OGTT; Visit 3 is for experimental testing to assess gain and the frequency range. Blood pressure, heart rate and muscle SNSA (MSNA) are measured during LBNP and OLBNP. MSNA is recorded using 2 microelectrodes inserted through the skin of the forearm to record activity (firing) of the median nerve. Blood samples are taken via IV placement to measure insulin and glucose during the OGTT for Visit 2, and then sex hormones and catecholamines during Visit 3. Results from the group of young trans men will be compared to a control group of cisgender women matched for age and body mass index.

    6. Conditions and Keywords

    Primary Disease or Condition Being Studied in the Trial, or the Focus of the Study
    Transgender Men, Blood Pressure, Hyperandrogenism
    Keywords
    transgender, baroreflex, testosterone

    7. Study Design

    Primary Purpose
    Basic Science
    Study Phase
    Not Applicable
    Interventional Study Model
    Parallel Assignment
    Model Description
    There is 1 group of trans men (n=20) and 1 group of cisgender women (n=20). Study procedures, protocols, and measurements will be the same for both groups and performed and/or taken in a similar time period.
    Masking
    None (Open Label)
    Allocation
    Non-Randomized
    Enrollment
    0 (Actual)

    8. Arms, Groups, and Interventions

    Arm Title
    Trans men
    Arm Type
    Active Comparator
    Arm Description
    transgender men taking physiologic doses of testosterone for gender affirming hormone therapy
    Arm Title
    control
    Arm Type
    No Intervention
    Arm Description
    cisgender women not receiving testosterone and with normal sex hormone levels
    Intervention Type
    Other
    Intervention Name(s)
    Trans men
    Intervention Description
    We are studying the effects of testosterone taken by trans men on mechanisms of blood pressure control and comparing those results to cisgender women that have normal (ie lower) testosterone levels.
    Primary Outcome Measure Information:
    Title
    Muscle Sympathetic Nerve Activity (MSNA)
    Description
    MSNA is recorded continuously at rest and during O/LBNP protocols with a tungsten microelectrode (0.2 diameters insulated shaft tapered to an uninsulated tip of ~1-5 μm) inserted percutaneously into the median nerve. Multiunit, postganglionic MSNA is distinguished from other sources of nerve activity by the presence of spontaneous pulse synchronous bursts, increased activity when the subject holds their breath or clenches their first (stretches forearm muscles around median nerve), or if activity does not change when the skin is stimulated by light brushing or stroking (indicates lack of skin nerve activity). Bursts of MSNA at rest and during LBNP are quantified as total activity (AU/min), burst frequency (bursts/min) and burst incidence (bursts/100 heartbeats). The MSNA burst incidence is expressed in bursts/100 heartbeats to normalize for differences in heart rate among subjects.
    Time Frame
    3 hours
    Title
    Systolic Blood Pressure (SBP)
    Description
    SBP is measured continuously with a Finometer beat-to-beat blood pressure measurement system at rest and during O/LBNP protocols. Units are mm Hg.
    Time Frame
    3 hours
    Title
    Diastolic Blood Pressure (DBP)
    Description
    DBP is measured continuously with a Finometer beat-to-beat blood pressure measurement system at rest and during O/LBNP protocols. Units are mm Hg.
    Time Frame
    3 hours
    Title
    Mean Arterial Pressure (MAP)
    Description
    MAP at rest and during O/LBNP protocols is calculated as 1/3(SBP-DBP)+DBP using the beat-to-beat SBP and DBP measurements taken with the Finometer system. Units are mm Hg.
    Time Frame
    3 hours
    Title
    Sympathetic Baroreflex (BR) Gain
    Description
    Sympathetic BR gain is used as an index of sympathetic (neural) control of blood pressure, where gain is determined by the slope of the linear relationship between MSNA (burst/100 heartbeats) and DBP (mm Hg) at rest and during LBNP. The relationship produces a negative slope in that for a given subject, when DBP falls below the normal level sustained at rest, sympathetic activity increases to restore DBP back to that normal level. Thus, more MSNA bursts are observed at lower levels of DBP and vice versa. A steeper (more negative) slope suggests greater sensitivity of the baroreceptors to changes in blood pressure, and thereby more effective sympathetic control of blood pressure. A flatter slope suggests impaired BR sensitivity and blood pressure dysfunction, which is expected for the trans men group compared to cisgender women controls.
    Time Frame
    3 hours
    Title
    Frequency in the Neural Cardiovascular Control
    Description
    The frequency of SBP, DBP and heart rate during OLBNP is analyzed in Matlab in a linear time-invariant system (LTI) framework. Heart rate and BP measures taken during OLBNP are low-pass filtered (0.05 Hz estimated example) and corrected for end-effects using a Hamming window. The derived impulse responses (IRs) are 1/3rd octave smoothed before calculating the frequency power spectra (0.001-0.05 Hz estimated example). The power of DBP and SBP at the OLBNP frequency are anticipated to be independently inversely related to the efficiency of BP control. Further, the difference in heart rate and SBP, and in heart rate and DBP, power at those frequencies reflects the degree of autonomic function, analogous to baroreflex gain.
    Time Frame
    0.5 hours
    Title
    Electrocardiogram (ECG)
    Description
    A 3-lead ECG is continuously recorded at rest and during the O/LBNP protocols. The R-wave of the QRS complex of the ECG recording will be used for measures of pulse interval by determining the amount of time in seconds between the R-waves of 2 consecutive QRS complexes.
    Time Frame
    3 hours
    Secondary Outcome Measure Information:
    Title
    Brachial Artery Mean Blood Flow Velocity
    Description
    Mean blood flow velocity in the brachial artery will be examined at rest and during LBNP using Doppler ultrasound velocimetry. Blood flow velocity spectra and arterial diameter are measured simultaneously with a Doppler probe and SonoScape S2 ultrasound system. The brachial artery is imaged with a 6.0-MHz linear array probe positioned at a 45° angle over the skin at the distal one-third of the upper arm. Brachial blood flow is expected to decrease as the level of LBNP increases and induces a greater orthostatic challenge. For example, blood flow would be highest at the -10LBNP stage and continually decrease during the following stages of -20, -30 and finally -40LBNP, where blood flow would be the lowest.
    Time Frame
    3 hours
    Title
    Cardiovagal Baroreflex (BR) Gain
    Description
    Cardiovagal BR gain is determined by the slope of the linear relationship between R-R Interval (seconds) and SBP (mm Hg) at rest and during LBNP. R-R Intervals are obtained from the ECG recording and SBP is obtained from the beat-to-beat measures taken by the Finometer.
    Time Frame
    3 hours

    10. Eligibility

    Sex
    Female
    Gender Based
    Yes
    Gender Eligibility Description
    Transgender men will be recruited for participating in the experimental group; cisgender women will be recruited for participation in the control group.
    Minimum Age & Unit of Time
    18 Years
    Maximum Age & Unit of Time
    45 Years
    Accepts Healthy Volunteers
    Accepts Healthy Volunteers
    Eligibility Criteria
    Inclusion Criteria: Both groups (trans men and cisgender women) must be healthy and non-smoking. Control participants must be cisgender women with regular menses every 26-34 days. Trans men participants must be currently receiving testosterone for gender affirming hormone therapy where physiologic doses of exogenous Dihydrotestosterone have been administered (via injection or transdermal application) for at least 3 months as prescribed by their local endocrine provider as part of their clinically indicated hormone therapy. Doses can vary depending on the size and goals of each patient, but blood testosterone will be between 400-1000 ng/dl. Exclusion Criteria: Subjects who smoke, have diabetes, or BP>140/90 will be excluded. Subjects will not be taking medications during the study, including any insulin-sensitizing or cardiovascular medications. Subjects are excluded if they have lost > 5 kg of weight within the past 6 months or perform high-intensity exercise > 3 times/week.

    12. IPD Sharing Statement

    Plan to Share IPD
    Undecided

    Learn more about this trial

    Mechanisms of Blood Pressure Dysfunction in Transmen Receiving Testosterone

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