The hypothalamus secretes gonadotrophin releasing hormone (GnRH) that stimulates the anterior pituitary gland to secrete follicle stimulating hormone (FSH) into the bloodstream which travels to the ovaries. FSH stimulates the development of a small number of follicles in the ovaries. One follicle will become the Graafian follicle. FSH also stimulates the cells of the growing follicles to secrete oestrogen. 

2 Day 6-10: Oestrogen causes the growth and repair of the uterine lining (endometrium). Oestrogen also inhibits the secretion of FSH from the anterior pituitary gland, thus preventing the development of more follicles. 

3 Day 11-17: When oestrogen levels increase to a high level, it triggers the secretion of luteinising hormone (LH) from the anterior pituitary gland that travels in the blood to the ovaries. LH causes the follicular wall of the Graafian follicle to rupture, releasing the secondary oocyte into the oviduct funnel (ovulation). This happens on the 14th day from the beginning of menstruation. After ovulation, LH causes the formation of an active corpus luteum from the ruptured follicle. The corpus luteum secretes progesterone and also some oestrogen.

4 Day 18-28: The progesterone secreted by the active corpus luteum keeps the uterine lining (endometrium) thick, well-supplied with blood (vascularised) and stimulates formation of glands secreting nutrients to prepare the endometrium for the implantation of the embryo if there is fertilisation. Progesterone also inhibits both FSH and LH production.

If fertilisation does not occur, the drop in LH level in the blood causes the corpus luteum to degenerate. When this happens, progesterone production stops, thus the uterine lining cannot be maintained in a thickened state anymore, so it breaks down. The lining is discharged with blood through the vagina. This is menstruation and it marks the beginning of the next cycle.

Once the supply side is in place, the demand side can be built through education. Targeted, culturally sensitive education – of men and boys as well as women and girls – works to decrease stigma and increase understanding of the usage, benefits and cost effectiveness of menstrual hygiene products such as reusable pads and menstrual cups. Greater understanding also decreases the stigma that women and girls may feel regarding buying menstrual hygiene products from a shop, and increases the likelihood that men in charge of a family’s finances will provide menstrual hygiene products to their female family members. Improved awareness among teachers can make it easier for girls to change/empty menstrual hygiene products in schools, though support from donors may also be required to fund the creation of suitable toilet facilities in schools for this to take place

https://www.heart-resources.org/blog/challenges-facing-women-girls-accessing-menstrual-hygiene-products-developing-countries-effective-approaches-increasing-access/.