Adaptions and Resiliency to Multi-Stressor OpeRations

Suppression of the reproductive hypothalamic-pituitary-gonadal (HPG) axis is a common physiological response to strenuous military training and can be difficult to replicate in simulated environments. Additionally, whether HPG suppression contributes to the physiological changes, performance decrements, and high MSK injury risk associated with multi-stressor military training is unknown. Thus, we will utilize pharmacological inhibition of the HPG axis to test if estrogen and testosterone replacement will mitigate injury risk and performance decrements following military-relevant multi-stressor training. This project aims to deliver a state-of-the-art evaluation of male and female adaptive responses to multi-stressor training and evidence-based guidance for the safe and ethical use of exogenous hormone replacement as a MSK injury mitigation solution during multi-stressor training and operations.

Inclusion criteria

• Age 18-40 years
• body mass index (BMI) 18-30 kg/m2
• weight stable (±10 lbs) in past 2 months
• takes part in moderate physical activity for at least 150 minutes/week
• currently free of upper or lower body /extremity injury or impairment
• able to commit to study duration
• agrees to adhere to study requirements
• not taking prescription medications or be willing to refrain from medication prior to and throughout the study period, unless approved by study physician
• in men, total testosterone concentration within normal physiological range (300-1000 ng/dL)
• in women, eumenorrheic (cycles of 26-35 days) and not using hormonal contraceptives for previous 3 months

Exclusion criteria

• Current smoker
• current clinical diagnosis of an eating disorder
• use of medication incompatible with measurement of reproductive and metabolic hormones or which may interfere with any of the study outcomes
• current oligo/amenorrhea in women
• any metabolic or endocrine disease
• has been diagnosed with a medical condition, physical or psychological, that currently prevents potential subjects from exercising
• currently pregnant or becomes pregnant during the study
• history of heart condition OR high blood pressure
• treating physician requires subject participates in medically supervised physical activity only
• history of drug addiction, or regular use of recreational drugs
• currently undergoing treatment for or have a history of mental health conditions
• irregular lab results (e.g., PSA >3 ng/mL)
• Current diagnoses of disorders known to affect bone metabolism including hyperthyroidism, hyperparathyroidism, osteomalacia, Cushing's, diabetes mellitus or renal insufficiency
• Current use of medications known to affect bone metabolism including estrogens, androgens, anti-estrogens, bisphosphonates (oral bisphosphonates within one year of the baseline visit or IV bisphosphonates within three years of the baseline visit), calcitonin, fluoride, oral or inhaled glucocorticoids, suppressive doses of thyroxine, lithium, pharmacological doses of vitamin D (greater than 2000 IU/day), anti-convulsants, depot medroxyprogesterone within 6 months.
• History of deep vein thrombosis, pulmonary embolism, or clotting disorders.
• History of stroke or myocardial infarction
• Serum 25-hydroxyvitamin D < 20 ng/mL
• Thyroid dysfunction
• Serum creatinine > 2 mg/dL
• Personal history or history of a first-degree relative with breast cancer
• Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) > 2x the upper limit of normal
• Serum bilirubin > 2 mg/dL
• Serum alkaline phosphatase > 150 U/L
• Plasma hemoglobin < 10 gm/dL
• Hematocrit > 50
• Fracture within the last 6 months.
• Serum testosterone level < 270 or > 1070 ng/dL
• Systolic blood pressure > 160 or diastolic blood pressure > 95
• Active substance abuse
• Triglycerides > 150 fasting
• History of hereditary angioedema
• History of chest pain at rest, during daily activities of living, or when performing physical activity
• Musculoskeletal injury removing subject from physical activity for more than a month within the past 2 years
• Recreational drug use more than 2 times per month in each of the previous 6 months
• Self-reported vision is worse than 20/20.
• Personal history or history of a first-degree relative with breast cancer
• Experienced a fracture within the last 6 months
• participated and taken investigational drug in any other clinical trial (including bioequivalence study) within six months prior to study drug administration
• Diagnosed with eating disorder
• Have food allergies, intolerance, restriction, or special diet needs
• History of endometriosis
• Current diagnosis of reproductive health issues, such as ovarian cysts, PCOS, pelvic lesions, undiagnosed ovarian enlargement
• Have undiagnosed abnormal vaginal bleeding
• Currently breastfeeding or within 2 months after stopping breastfeeding
• Have dietary restrictions