Objective: Cystic fibrosis-related diabetes (CFRD) affects up to half of the people with cystic fibrosis (CF) by adulthood. CFRD is primarily caused by pancreatic dysfunction that leads to insufficient insulin release and/or insulin resistance. Exocrine pancreatic insufficiency in people with CF is associated with fat-soluble vitamin malabsorption, including vitamins A, D, E, and K. This study examined the relationship between vitamin D status, assessed by serum 25-hydroxyvitamin D (25(OH)D), and the development of CF-related diabetes (CFRD) in adults with CF. Methods: This was a retrospective cohort study of adults seen at a single CF center. The data were extracted from the electronic medical records and the Emory Clinical Data Warehouse, a data repository of health information from patients seen at Emory Healthcare. We collected age, race, the first recorded serum 25-hydroxyvitamin D (25(OH)D) concentration, body mass index (BMI), and onset of diabetes diagnosis. Log-rank (Mantel–Cox) tests were used to compare the relative risk of CFRD onset in the subjects with stratified vitamin D status and weight status. A sub-group analysis using chi-square tests assessed the independence between vitamin D deficiency and CFRD risk factors, including gender and CF mutation types (homozygous or heterozygous for F508del, or others). Unpaired t-tests were also used to compare the BMI values and serum 25(OH)D between the CF adults based on the CFRD development. Results: This study included 253 subjects with a mean age of 27.1 years (±9.0), a mean follow-up time period of 1917.1 (±1394.5) days, and a mean serum 25(OH)D concentration of 31.8 ng/mL (±14.0). The majority (52.6%) of the subjects developed CFRD during the study period. Vitamin D deficiency (defined as 25(OH)D < 20 ng/mL) was present in 25.3% of the subjects. Close to two thirds (64.1%) of the subjects with vitamin D deficiency developed CFRD during the study. Vitamin D deficiency increased the risk of developing CFRD (chi-square, p = 0.03) during the course of the study. The time to the onset of CFRD stratified by vitamin D status was also significant (25(OH)D < 20 ng/mL vs. 25(OH)D ≥ 20 ng/mL) (95% CI: 1.2, 2.7, p < 0.0078). Conclusion: Our findings support the hypothesis that adults with CF and vitamin D deficiency are at a higher risk of developing CFRD and are at risk for earlier CFRD onset. The maintenance of a serum 25(OH)D concentration above 20 ng/mL may decrease the risk of progression to CFRD.
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).
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