Context: Recent in vitro and in vivo experimental evidence supports a role of vitamin D insufficiency as an important factor in the development of uterine leiomyomas. However, epidemiological data supporting this possibility are scanty.
Objective: Our objective was to investigate vitamin D status in women with and without uterine leiomyomas.
Design: This was a case-control study of women referring to 2 infertility units in Italy. Women were eligible as cases if they were diagnosed with at least 1 uterine leiomyoma with a mean diameter ≥10 mm at transvaginal ultrasound. Each of them was matched to the 2 subsequent women of the same age (±1 year) whose uterus resulted unremarkable at ultrasound. Selected women provided a blood sample for the quantitative detection of 25-hydroxyvitamin D₃ levels.
Main outcome measure: We measured serum concentration of 25-hydroxyvitamin D₃.
Results: A total of 128 women with leiomyomas and 256 controls were selected. The mean ± SD serum concentration of 25-hydroxyvitamin D3 was significantly lower in affected women compared with controls (18.0 ± 7.7 vs 20.8 ± 11.1 ng/mL respectively, P = .010). The number (proportion) of women with 25-hydroxyvitamin D3 deficiency (ie, <10 ng/mL) in cases and controls was 19 (15%) and 19 (7%), respectively (P = .022). The adjusted odds ratio for the presence of leiomyomas in women with serum levels of 25-hydroxyvitamin D₃ deficiency was 2.4 (95% confidence interval = 1.2-4.9) (P = .016).
Conclusions: Vitamin D is an emerging regulator of uterine leiomyoma development. Cohort and interventional studies are pressingly needed to confirm a causal relationship and to investigate the potential therapeutic benefits of vitamin D supplementation.