Association Between Vitamin D and the Risk of Uterine Fibroids

Inclusion Criteria: 1. Volunteer to participate in the study with informed consent; 2. Females aged 35-50 who are confirmed with a normal, fibroid-free uterine structure, by means of transvaginal or abdominal ultrasonography; 3. Serum25-hydroxyvitamin D3 \<20 ng/ml, ≥ 12ng/ml. Exclusion Criteria: 1. Use of sexual hormone, mifepristone, gonadotropin-releasing hormone agonist (GnRHa), or other medication which is likely to interfere with uterine fibroids within 3 months; 2. Pregnancy, lactation, postmenopause, or planned pregnancy within two years; 3. Allergic to vitamin D3; 4. Suspected or identified as other tumors of genital tract; 5. History of hysterectomy or myomectomy; 6. History of osteoporosis or vitamin D deficiency taking vitamin D supplements within previous one month; 7. History of hyperparathyroidism, infectious diseases (tuberculosis, AIDS), autoimmune diseases, or digestive system diseases (malabsorption, crohn disease and dysentery); 8. Alanine aminotransferase (ALT) or aspartate transaminase (AST) more than 3 times of the normal upper limit, total bilirubin (TBIL) more than 2 times of the normal upper limit; 9. Creatinine levels ≥ 1.4 mg/dL (123μmol/L) or creatinine clearance ≤ 50 ml/min; 10. History of malignant tumors; 11. Simultaneous participation in another clinical study with investigational medicinal product(s) or researcher thinks the subjects are not suitable for this trial.