An Investigation of the Effects of Melatonin and Vitamin D on the Ovaries of a Rat Model of Premature Ovarian Failure Induced by Cyclophosphamide

In this study, we evaluated the protective effects of combined melatonin and vitamin D3 treatment on ovarian reserve and tissue architecture in a cyclophosphamide-induced premature ovarian failure (POF) rat model. Forty-nine adult female rats were randomly assigned to seven groups, including intact control (group 1), single-agent control (groups 2 and 3), POF (group 4), and POF + treatment (groups 5, 6, and 7) groups. Cyclophosphamide exposure led to elevated FSH and LH levels, reduced estradiol and progesterone levels, extensive follicular atresia, stromal fibrosis, and the marked degeneration of the ovarian ultrastructure. Additionally, the expression levels of PTEN, FOXO3a, and AMH were significantly downregulated, while caspase-3 and TNF-α immunoreactivities were increased. Notably, co-treatment with melatonin and vitamin D3 preserved primordial and growing follicle populations, restored hormonal balance, reduced stromal fibrosis, and attenuated apoptosis and inflammation markers. These findings highlight the potential of combined melatonin and vitamin D3 therapy as a fertility-preserving strategy that functions by mitigating chemotherapy-induced ovarian injury through multi-pathway modulation.