Objective: The aim of this study was to detect the effect of vitamin D (Vit. D) intake on the mid-luteal estradiol (E2), and progesterone (P), and the relation between vit. D, and the adolescents' mid-luteal E2, and P.
Patients and methods: Eighty-five (85) adolescents were recruited for this cohort study after obtaining informed consent. After a detailed history and clinical examination, the body mass index (BMI) of the studied participants was calculated, followed by pelvic sonography to exclude any pelvic pathology. Participants' blood samples were collected on days 21-22 of the menstrual cycle (mid-luteal) to measure the thyrotropin (TSH) (i.e., to exclude hypothyroidism), prolactin (i.e., to exclude hyperprolactinemia), glycosylated hemoglobin (HbA1C), (i.e., to exclude diabetes), E2, P, and 25(OH)D. Participants received 50,000 IU of vit. D weekly for two months, and on the 3rd month, the mid-luteal E2, P, and 25(OH)D were measured. The mid-luteal E2, P, and 25(OH)D were compared before and after the vit. D intake to detect the effect of vit. D intake (50,000 IU weekly for 2 months) on the mid-luteal E2 and P (primary outcome). Additionally, the relations between vit. D and the adolescents' mid-luteal E2 and P were detected as secondary outcomes using the correlation analysis (Pearson's correlation).
Results: The mid-luteal E2 and P statistically decreased from 109.3±15.7 pg/mL and 9.8±1.01 ng/mL, respectively to 40.7±10.52 pg/mL, and 5.2±0.73 ng/mL, respectively, after vit. D intake (p=0.00015; 95% CI: 64.5, 68.6, 72.7, and p=0.0016; 95% CI: 4.3, 4.6, 4.87, respectively). Significant negative correlations between the 25(OH)D, and both the mid-luteal E2 (r -0.661; p<0.00001), and P (r -0.521; p<0.00001) were detected in this study.
Conclusions: The mid-luteal E2 and P statistically decreased after vit. D intake (50,000 IU of vit. D weekly for 2 months). Significant negative correlations between the 25(OH)D, and both the mid-luteal E2 and P were detected in this study. The relation between vit. D and ovarian steroids, and the effect of vit. D intake on ovarian steroids need further larger studies.