Mention the relationships between pituitary and ovarian hormones during a menstrual cycle.

The relationship between pituitary and ovarian hormones during a menstrual cycle is as follows:

The menstrual cycle is the regular change that occurs in the female reproductive system after a woman has attained puberty. The menstrual cycle occurs due to the rise and fall of different hormones of the pituitary and ovary. After the menstrual phase, the follicular phase follows. Here, the primary follicles in the ovary grow to become a fully mature Graafian follicle and at the same time, the endometrium of uterus regenerates. These changes that are brought about in the ovary and the uterus are induced by changes in the levels of pituitary and ovarian hormones.

The secretion of Luteinising hormone(LH) and Follicle Stimulating Hormone(FSH) - pituitary hormones increase gradually during the follicular phase, and in turn, stimulates follicular development as well as secretion of estrogens by the follicles which are growing. Rapid secretion of LH leads to LH surge that induces rupture of Graafian follicle releasing the ovum (ovulation). The ovulatory phase is followed by the luteal phase during which the remaining parts of the Graafian follicle converts to the corpus luteum that produces large amounts of progesterone (ovarian hormone) that maintains the endometrium which is necessary for implantation of the fertilised ovum. Oestrogen (ovarian hormone) is responsible for repairing damaged tissues of the uterus and fallopian tubes after menstruation, etc.

The diagram below shows the various phases in the menstrual cycle as well as the hormone levels during these phases.