Which structure least influences the human female menstrual cycle?

The structure that least influences the human female menstrual cycle is the adrenal glands. While they produce hormones such as androgens and cortisol, their impact on the menstrual cycle is minimal compared to the primary roles of the ovaries and the hypothalamus-pituitary axis. The ovaries are crucial for hormone production and ovulation, while the hypothalamus and pituitary gland regulate the hormonal signals that control the cycle.