Roles of Hormone in Menstrual Cycle

Menstrual cycle consists of 4 phases:
a) Follicular phase
b) Ovulation
c) Luteal phase
d) Menstruation

• Hypothalamus secretes GnRH(gonadotrophin releasing hormone).
• GnRH stimulates anterior pitituary gland to secrete FSH(follicle-stimulating hormone) & low levels of LH(luteinising hormone).
• FSH stimulates development of follicles in ovary. Only one follicle will mature to form Graafian follicle.
• Follicles secrete oestrogen.
• Oestrogen causes healing & repair of uterine lining. At low levels, secretion of FSH & LH are inhibited. At high levels, secretion of LH is stimulated, causing ovulation. Secondary oocyte is released  into fallopian tube.
• LH stimulates convertion of empty follicle into corpus luteum & stimulate corpus luteum to produce oestrogen & progesterone.
• Both oestrogen & progesterone promotes thickening of endometrium/uterine lining to prepare for the implantation of blastocyst.
• Oestrogen & progesterone also inhibits secretion of FSH & LH. Development of new follicles is prevented.
• If fertilisation does not occur, corpus luteum degenerates. Oestrogen & progesterone decreases. Endometrium breaks down. Menstruation occurs.