Findings from a feasibility study of estradiol for hypogonadal women with cystic fibrosis-related bone disease

BACKGROUND: Advancements in therapies for patients with cystic fibrosis (CF) have decreased mortality, leading to increased prevalence of chronic complications including bone disease. CF-related bone disease (CFBD) is characterized by low bone mineral density (BMD) and fragility fractures. Estrogen deficiency increases bone resorption, resulting in decreased BMD that can be restored with estrogen replacement. Current CF guidelines recommend treating female hypogonadal patients with CFBD with estrogen replacement, but no prospective study has investigated the effects of estrogen supplementation on CFBD. Estrogen is known to modulate inflammatory markers and autoimmune diseases. We proposed to test the hypothesis that estrogen status plays a critical role in optimizing bone health, modulating inflammation, preserving lung function, and maximizing quality of life in premenopausal women with CF. METHODS: We planned a randomized, placebo-controlled, investigator- and patient-blinded, pilot trial with two parallel arms. Eligible subjects were women with CF 18–50 years old with hypogonadism and low BMD who were not taking systemic glucocorticoids, had not had a prior transplant, and did not have contraindications to oral estradiol. Subjects would be block randomized to receive oral estradiol or placebo for 6 months. The primary outcome was feasibility metrics. Secondary outcomes included relative changes in estradiol, bone turnover markers, lung function, inflammatory markers, and quality of life metrics. The study was funded through departmental funds. RESULTS: Of 233 subjects screened, 86 subjects were women with CF 18–50 years old and none were eligible for participation. Most subjects were excluded due to absent DXA report (24%), normal BMD (22%), or use of systemic estrogen (16%). Due to difficulty recruiting the planned 52 subjects, the trial was closed for recruitment and no subjects were randomized. CONCLUSION: This study was designed to investigate the feasibility of a safety and efficacy trial of estrogen therapy for women with CF. Unfortunately, due to eligibility criteria, the study was unable to recruit subjects. This feasibility study highlights the need for improved BMD screening in young women with CF. Future study designs may require the incorporation of a screening DXA as part of subject recruitment. TRIAL REGISTRATION: The study was registered on ClinicalTrials.gov (NCT03724955).