Changes in Energy Expenditure (EE) in Transsexuals Undergoing Hormonal Therapy

Study Objective

1. To assess energy expenditure including: resting energy expenditure (RER), - in transgender subjects undergoing hormonal gender affirming treatment.
2. To assess change in Physical Activity (PA) before and after treatment. Methods Study design: A pilot observational prospective study, recruiting 20 transsexuals: 10 transwomen (TW) and 10 transmen (TM).

Criteria for inclusion

1. TW and TM with no prior hormonal therapy in the last one year.
2. Stable weight in last six months (<±5% weight change),

Criteria for exclusion

1. Postmenopausal TM.
2. Oral contraceptive use.
3. Pregnancy or breastfeeding.
4. Glucocorticosteroid treatment
5. Uncontrolled thyroid disorders
6. Use of drugs that potentially impact body metabolism Follow up will be for 6 months.

Baseline tests and after 3 and 6 months of treatment:

1. Anthropometrics:
2. Body weight will be measured to the nearest 10 g on a digital scale (Seca, 'mBCA') after 12 hours of overnight fast.
3. Height will be measured with a wireless digital stadiometer (Seca 274) to the nearest 0.1 cm at baseline.
4. Changes in body composition, including Fat and Fat Free Mass, will be evaluated by multi-frequency bioelectrical impedance analysis (BIA) after 12 hours fasting, using the 'mBCA' body composition analyzer.
5. Waist and hip circumference will be measured with a tape measure
6. Resting blood pressure - diastolic and systolic, and heart rate will be measured by a completely automated device (Omron, M7) after sitting at least 10 min without distractions (e.g. cell phones). Body weight, waist and hip circumference, body composition, blood pressure and resting heart rate measurements will be made pre and 3, 6 months post therapy.
7. Fasting (12 hours) blood tests pre and post therapy: (Blood tests will take place in the endocrinology institute in Ichilov hospital.)
8. Hormone analysis: TSH T4FREE T3, CORTISOL LH FSH ESTRADIOL PROGESTERONE, testosterone, bioavailable testosterone, DHEAS
9. Clinical chemistry: electrolytes, kidney function tests, liver function tests
10. Complete blood count
11. Lipid profile
12. Glucose and HbA1c-levels, INSULIN
13. Fecal microbiota pre and post therapy
14. Measurement of REE will be measured over a 60-minute period using whole-room indirect calorimeter (WRIC) Participants will enter the WRIC at 7am after overnight 12 hours of fasting and at least 24 hours after the last bout of any structured exercise, with instructions to avoid unnecessary activity on the morning of testing, . They will then be instructed to maintain a supine position until 8pm for measuring REE.
15. Changes in daily physical activity and sedentary behavior will be assessed for 7 days pre- and post- hormonal therapy by a tri-axial accelerometer (ActiGraph GT9X Link, Pensacola, Florida).

Whole human room calorimetry The REE will be measured by indirect calorimetry in a small WRIC (~11,500 liters) pre and post hormonal therapy. Air in the calorimeter will be removed at 240 L/min. Oxygen uptake and carbon dioxide production will be measured using gas analyzers (Promethion room calorimeter systems) and calculated by ExpeData software (Sable Systems, USA). The O2 and CO2 gas analyzers will be calibrated using dry chemicals before each experiment, and once a week by using standardized gas mixtures. To calculate EE we will use the Weir's equation (EE = 3.9 × VO2 (L) + 1.1 × VCO2 (L)) and the respiratory quotient (RQ) will be calculated as VCO2/VO2. The accuracy of the WRIC for the measurement of EE, determined repeatedly using a 3 hours N2 injection test, was 99.4% ± 2.6% for O2 consumption. For the duration of the test, the participant will be asked to remain motionless and awake in a supine position, lightly clothed in a thermoneutral (22°C-23°C), dimly lit and quiet room.

Statistical Analysis We plan on using two-tailed tests in SAS with α=0.05. Power analysis indicates that 10 individuals will be needed to have 80% power to detect an 80 kcal/day difference in 24-hr energy expenditure (the primary endpoint), based on unpublished data indicating a within-subjects standard deviation of σ=79 kcal/day (Ravussin et al. 2019). Baseline data and the data for each arm will be reported in the text as raw mean ± SD, while the treatment effects or differences between arms (denoted Δ) are reported as least squares mean ± SEM. The treatment effects and associated p-values were computed using linear mixed models with heterogeneous compound symmetry, with participants as the random effect and the treatment, period, sequence, and BMI as fixed effects, using the Satterthwaite method for calculating degrees of freedom.