I have written before that vitamin D increases testosterone levels in men. It is not a minor effect.
Now, a group in Canada, led by Dr. Julia Knight at Mount Sinai Hospital, 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%. Unlike men, the study was confounded by what estrous cycle phase the women were in.
The favorable implications for breast cancer come immediately to mind, but as an old GP, I can tell you that lower female hormones sometimes help women in all kinds of ways, including psychologically. I suspect the women also became more fertile.