Vitamin D is not only essential for bone health, but has recently been known to play an important role in blood pressure, blood sugar control, and immune function, and is even known to be related to cancer, autoimmune diseases, obesity, female reproduction, and depression. In particular, interest has recently increased in the potential role of vitamin D in female reproduction and mental health. Although not yet clearly known, results are accumulating suggesting that vitamin D deficiency may alter ovarian function and may also be related to depression. Ovarian function represents the degree of ovarian aging and can be estimated as an ovarian reserve markers. Interestingly, the relationship between female hormonal changes and depression has already been established in many studies, so proving the role of vitamin D in their relationship could be key to explaining female hormone-related depression. In this book, you will explore the known roles of vitamin D in women's reproductive function, and depression, along with recent two studies on vitamin D's link to ovarian reserve markers and depression.