PLOD1 and hyperprolactinemia: Occasional anovulatory cycles are normal in otherwise regularly ovulating women and they are a complex and heterogeneous phenomenon, resulting from various forms of hypothalamic dysfunctions, hyperprolactinemia, excessive LH and androgen concentrations, lack of progesterone, or constantly elevated estrogen levels [52]; hence, the hormonal profile across an anovulatory cycle can be substantially different compared to the ovulatory cycle.