Cancer Causes Control 2010 Mar;21(3):479-83.
Pub Med: Link
Vitamin D association with estradiol and progesterone in young women
Knight JA, Wong J, Blackmore KM, Raboud JM, Vieth R.
Prosserman Centre for Health Research, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.
CONCLUSIONS: Higher levels of vitamin D may reduce progesterone and estradiol, providing a potential mechanism for reduction in breast cancer risk from increased vitamin D exposure in young women.
**They discovered that administration of 24,000 IU/week for four weeks was associated with lower estrogen levels and progesterone levels. Per 4 ng/ml increase in vitamin D, progesterone levels decreased by 10% and estrogen decreased by 3%.
Vitamin D may reduce breast cancer risk through an effect on steroid hormones in cycling women.We conducted a study to determine whether there is an association between circulating 25-hydroxyvitamin D (25(OH)D) and estradiol and progesterone in young women.
Volunteer women aged 18-22 and not using hormonal contraceptives were recruited during summer and winter. They provided demographic and lifestyle information and a blood sample. Women recruited in winter gave a second sample after taking vitamin D supplement for 4 weeks. There were 101 women sampled during the luteal phase (1-14 days prior to the start of the next menstrual period). Generalized estimating equation linear regression models were used to examine the relationship between 25(OH)D and estradiol and progesterone.
Per increase of 10 nmol/l of 25(OH)D, progesterone multiplicatively decreased by a factor of 10% (95% CI 5-14%, p < 0.001) and estradiol decreased by a factor of 3% (95% CI 0-6%, p = 0.04) after adjustment for age, body mass index, ethnicity, season, alcohol use, smoking, and physical activity.
Another good article: Vit. D-What We Have Learned About Vitamin D Dosing?